However, it turns out that lots of indoor growers (especially those growing short-cycle plants) choose a different route. In short, they reuse their growing media! And before you think this is just the preserve of penny-pinching hippies, it turns out that it’s not all about saving a few dollars – it could increase your yields too!

Aha, there we go … increased yields … that’s all we needed to say wasn’t it?

What is Coco Coir?

Grab some coco coir out of the bag and, at first glance, it looks like soil. But it isn’t.

It’s actually a bi-product comprised of the fibrous husk of … you guessed it … coconuts. From this husk three main horticultural coir products can be acquired; coir chips, coir fiber or coir pith/dust. The latter dust retains water well while the fibers and chips help with air space and drainage. Many mixes and grades of coco coir are on sale in grow stores, variations of coir media exist to suit the irrigation strategy or hydroponic system of the grower.

Coco coir dust is the major constituent of most coir products and is composed of millions of capillary micro-sponges that absorb and hold up to nine times its own weight in water. It has a natural pH of around 5.7 to 6.5, plus a good cation exchange capacity or ‘CEC’ (how easily it gives up nutrients to the plant’s roots), making it ideal for hydroponic cultivation.

Plants grown in coir can develop large roots, stems and blooms. Unlike regular potting soil, which can easily become compacted, coco coir has plenty of air spaces for plant roots, giving rise to a healthy aerobic rhizosphere—essential for favorable nutrient and water uptake. Coco coir has a naturally high lignin content which encourages favorable micro-organisms around the roots and discourages decomposition, making it an ideal growing media for reuse.

Buffered and Non-Buffered Coco Coir

Coco coir in its natural state contains a lot of sodium ions, which cling to the coco coir like a magnet on the cation exchange sites, and is also rich in potassium. In order to make coco coir suitable for use as a growing media it must be pretreated or ‘buffered’ before use. The buffering process involves pre-soaking the coir for 12-24 hours with a buffering solution high in calcium; this displaces the sodium and balances the naturally occurring potassium. After the soaking period the media is washed with water, this removes the displaced sodium, leaving the calcium in the coir. This buffering process prevents unwanted draw down or ‘lockout’ of calcium and magnesium, and avoids sodium toxicity issues. Luckily for us home growers, most pre-packaged coir products in grow stores are buffered at the point of manufacture and will be ready to use, however; it doesn’t hurt to check the packaging before use!

In the early days when coir was first introduced into the hydroponic market, the pretreatment process was overlooked. Young non-composted and non-buffered coir products were sold without instruction and many growers suffered major nutrient issues and lost crops. Although these days are behind us, this initial introduction to coir tarnished its reputation as a quality growing media for many years.

It’s worth pointing out that not all growing media is suitable for re-use. So first, here’s what you should factor into your evaluation:

1.            Structure stability

2.            Nutrient retention

3.            Practicality

Now let’s look at coco coir in these three terms. Coco coir, as a soilless growing media, is usually a mix dust and fiber, but some mixes can also contain larger coir chips.

1.            Structure

Good quality, buffered coco coir, will keep most of its attributes throughout its useable life. However, the structure of steam sterilized coco coir will degrade faster than its un-cooked counterpart. For the purpose of this discussion we will assume that the coco coir is soft water washed, unpasteurized and chemically buffered; this represents the majority of coir available to hydroponic growers. Coco coir’s miniature “sponges” will become misshaped and smaller towards the end of their life, resulting less air space between particles and an overall higher water holding capacity. Even though this is a slow process some adaptation in watering may be required. After using coir for short cycle crops, amendments with 10-20% fresh coir or perlite may be required when being reused for the 3^rd and 4^th cycle. Care must be taken with the irrigation regime and nutrient program to insure coir has an adequate life span. Principally, good watering practices and monitoring run-off EC (keeping it within optimal range) will permit seamless re-use.

2.            Nutrient Retention

Buffered coco remains relatively chemically stable throughout its life, particularly when used with a coco coir specific nutrient; formulated to complement the unique cation exchange properties of the media. Coco coir can be easily EC controlled by monitoring the EC of the run-off.  Watering with a low EC nutrient solution will reduce its EC without rinsing off the famous buffer.  If plain water is used in excess, the coir may be rendered chemically imbalanced and may create problems in subsequent culture.  On the other hand, coir reacts quickly to low EC rinse and thus it requires much less run-off than peat mixes.  Unpasteurized coco coir is also a very hospitable substrate for its natural beneficial fungal inhabitant trichoderma, making it a very disease resistant and root protective growing medium.

3.            Practicality

The widely held belief in the gardening industry is that coir may be used for up to one year, or three to four crops for short cycle plants, without any compromise on crop quality. Others growers claim that they have successfully re-used coir for years. The amount of times that coir cam be utilized ultimatly depends on the initial quality of the coir and the steps taken to prepare the media between each use. The first thing that must be done is the removal of dead cellulose e.g. root matter left over from previous plants. To remove the large roots the coco coir can be broken up, passed through a ¼ inch soil sieve and larger roots can be discarded. Enzyme products (e.g. CANNAZym, Hygrozyme / Grozyme, or Multi Zen) when applied in the latter stages of the crops cycle will do a sufficient job of cleaning up the residual decaying material. It is not advisable to have lots of dead roots remaining in the media because they can contribute to an anaerobic (low oxygen) environment. Once the root material has been disposed of, coco coir should be flushed with water or a low EC nutrient solution to bring the nutrient levels back down to an acceptable range.

Preparations and Considerations

Once the media is ‘clean’, the addition of beneficial microbes is highly recommended. Coco is an ideal environment for beneficial bacteria and fungi, in particular, the introduction of trichoderma and mycorrhizal fungi will help maintain good growth and disease resistance. Inoculating coco coir with beneficial fungi also has great benefits when re-using the media, as fungal colonies improve with time.

The key component to how long coco may be reused all has to do with how far it has decomposed naturally. Coir does decompose when wet over a period of time. Unfortunately, fungus gnats thrive in the presence of decaying organic matter, and coir is a perfect environment for them. Making sure that all the dead roots are removed, the coir isn’t over-watered and a using dry mulch of coir chips or clay pebbles on the surface of the media will all help to prevent fungus gnats. Utilizing certain “drench” products definitely controls gnat populations, along with sticky traps and the natural predator Hypoaspis miles.

IMPORTANT: You should not reuse coco coir if you encountered any pathogenic or root insect issues during a cycle.

Conclusion

Coco can often produce better results on the second or third use; this can be due to a number of factors.  Coir can get better after the first successful crop because there will be a stable balance of ions on the cation exchange sites, leading to subsequent crops starting life with an improved root environment. Another reason growers often see improved results is due to the beneficial microbes present in media, these take time to develop and flourish; particularly mycorrhizae and Trichoderma, which can reach much higher potentials for growth improvement over longer time frames. However, an alternate explanation might be that the original coir coco was too young in decomposition first time round and may have degraded in a favorable way after reuse.

Crops that went through a flush period at the end of a crop cycle fair better because salt levels are reduced during the leaching process. Salts are constantly given off by coco coir as it decomposes, mainly potassium and sodium. Since the medium decomposes throughout its life, this process is continuous. Washing the media out well before planting should mitigate any negative effects. Reusing coir that has not been flushed often results in nutrient imbalance and over-fertilization issues. However, it should be noted that the presence of some of these ions is what buffers the coco. If you lose this buffer you return to calcium and magnesium lockout and pH issues of untreated coco.

In summary, coco has great potential as a reusable media, but to what extent is dependent on the motivation of the gardener. Should a gardener decide that the preceding is too much trouble, coco may always be reused as a soil improver for outdoor plants as well as a ‘brown’ high carbon addition to compost piles.

About the authors:
Robert Hunt is the owner of Rocky Mountain Hydroponics in Golden and Edwards, CO and of Evergreen Garden Center in Portland, ME. Zac Ricciardi is the products trainer for Rocky Mountain Hydroponics in CO.

For those not familiar with Sure To Grow, allow me to enlighten. Plastic bottles are recycled and reconstituted into a growing medium that is Sure To Grow (STG). The medium feels light and fluffy. You can purchase it in any form factor that you need: sheets, blocks, loose-fill, and pre-formed cones for net pots (2″ seedling pucks up to 10″ for 2-gallon buckets).

In contrast to other mediums, raw materials are not utilized in the creation of Sure to Grow. Reduce, recycle, and reuse. Plastic bottles feed Sure To Grow. However, the tradeoff of utilizing raw, virgin ingredients which can be reused vs. waste products which would otherwise be thrown away—-I choose the medium from waste recycled products.

Why is it a great growing medium?

One of the single most important and hard-learned benefits of Sure to Grow—-plant resiliency. During the 2 years that I’ve been using Sure To Grow, I’ve had root rot occur twice. The roots started in STG popped back almost instantly. No other medium that I tried worked this well.

The reason why this occurred is that the roots were protected in the bubble that is Sure To Grow. With Hygromite (diatomaceous earth) and Hydroton (clay pebbles), root rot affected the roots up to the root ball. With Sure To Grow, root rot stopped at the medium. After trimming the foliage and affected roots, roots took 4x as long to restore with Hygromite and Hydroton than with Sure To Grow.

With STG, the entire plant didn’t have to start rerooting from scratch. The new rooting started right from the edge of the medium. BAM! Almost. . .insta-re-rooting.

Here we have a couple of pics of plants that suffered from root rot.  These shots are after 1 week and 2 weeks, respectively, from Sure to Grow in Current Culture H2O’s 4XL system.

Transplantability. Say you start your plant in dirt, or any other medium and you want to change it up. You can repot your plant into STG. You carve out a suitable cavern inside STG and insert your plant.

Transplant from dirt? Impossible, you say! Possible, says I. Sure To Grow functions as a micro-filter. Wash away what soil that you can, carve out a suitable pocket—without permeating the medium’s shell—and you have a nice home for your previously soil-based plant. The soil will not flow out of the STG to muck up your growing system. Except for the normal transplant adjustment, the plants take to it like ducks to water.

“

How to improve it?

STG cannot support larger, heavier plants on its own. Unless there is a stiffer superstructure around the medium (i.e. net basket, tomato cage, etc.), a heavy plant will topple in this medium. As plants grow larger, their root structure will firmly hold them in place. I don’t know that it’s possible, but a denser, heavier Sure To Grow would solve this.

Conclusion

For me, perfect growing materials utilize waste from other processes. Compost from kitchen scraps, manure from animals, and garden beds from old railroad ties are all perfect. So is Sure To Grow. Recycled plastic bottles transformed into a growing medium. Awesome!

No virgin rocks or wooly sheep were hurt in the writing of this article.

Happy Gardening!

Curtis

Jargon Buster

Cation Exchange Capacity – CEC
The ability of a growing media to hold and release positive charged elements (cations). Important nutrient cations include calcium, magnesium, sodium and potassium. Growing media with a low CEC allows cations to be easily leached away whereas growing media with a high CEC withhold cations and act as a long term store.

Air Filled Porosity – AFP
The amount of air space in the growing media.

Water Holding Capacity – WHC
The ability of a growing media to hold and store water.

Coco Fiber (Coir)

What is it? The shredded inner pith of the coconut husk
Where does it come from? Mostly from coconut palms in Sri Lanka and India.
Cost? $13–$50 (3 cu. ft.)
Reusable? Yes
pH: 6.0
CEC: Medium
AFP: Medium
WHC: High
Pros: Naturally contains the beneficial fungus Trichoderma, slowly releases potassium.
Cons: Draws down calcium, easily over-watered.
Irrigation: Manual top-fed, ebb/flow, drip.
Nutrient Requirements: Many growers choose coco coir specific nutrients, others add calcium-magnesium additives.
Usage notes: Coco coir comes in various compressed forms: bricks, bales and slabs. Also available in ready to use loose fill bags.

Coco Chips (Croutons)

What is it? Cube-shaped coconut husk chips
Where does it come from? Mostly from coconut palms in Sri Lanka and India.
How much? Around $65 (3 cu. ft.)
Reusable? Yes
pH: 6.0
CEC: Medium
AFP: High
WHC: Very low
Pros: Naturally contains the beneficial fungus Trichoderma, slowly releases potassium, natural alternative to clay pebbles.
Cons: Tends to float when flooded, needs frequent irrigation.
Irrigation: Ebb/flow, drip
Nutrient Requirements: When using on their own consider incorporating a calcium-magnesium additive to your nutrient regimen.
Usage notes: Excellent for mixing with coco coir fiber to lower the WHC, ideal for using as a mulch on the top of other growing media; excellent for growing orchids.

Vermicrop’s Coco Not

What is it? a soilless medium made from the bark of sustainably harvested redwood trees blended with the fibers of a Kapok fruit
Where does it come from? Mostly California
How much? TBC
Reusable? Yes
pH: Normally 5.5 but increased to a range of 6-7 with oyster flour.
CEC: Low
AFP: Medium
WHC: Low
Pros: Locally made, natural and organic
Cons: Low water retention
Irrigation: Manual top-fed, ebb/flow and DWC
Nutrient Requirements: no special requirements
Usage notes: Does not need to be rinsed but should be fed water only for the first 5-10 days

Perlite

What is it? Superheated and expanded volcanic glass
Where does it come from? Produced worldwide but now mostly in China.
How much? $45 3 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High-medium
WHC: Medium
Pros: Lightweight, readily-available, great for rooting cuttings
Cons: Has no buffering qualities, leaches nutrient easily and tends to float when flooded
Irrigation: Manual top-feed, Drip, ebb/flow and aeroponics
Nutrient Requirements: Naturally Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Perlite is available in many grades. 4-12mm is most common for horticulture. Perlite can be used alone or amended into coir, vermiculite, peat moss, or soil mixes to improve aeration/drainage. A 50/50 mix of perlite and vermiculite is ideal for rooting most cuttings.

Vermiculite

What is it? A natural micaceous mineral that expands when heated
Where does it come from? South Africa, China, USA, or Brazil
How much? $40 (3 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Medium
AFP: Medium-Low
WHC: High
Pros: Lightweight, excellent buffering qualities
Cons: Easily over-watered,
Irrigation: Drip, ebb/flow, and manual top-feed
Nutrient Requirements: Naturally Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Used neat, vermiculite holds too much water for most plants’ needs. Amendment is necessary (see also perlite)

Diatomaceous Earth

What is it? A sedimentary rock made from fossilized remains of diatoms
Where does it come from? Worldwide
How much? $55 (40 litres)
Reusable? Yes
pH: Neutral
CEC: Medium
AFP: High
WHC: Medium-low
Pros: Does not roll, contains silica, sterile (but harbors beneficials well), holds more water than clay pebbles
Cons: Heavy weight; releases sediment
Irrigation: Ebb/flow, drip, DWC, aeroponics
Nutrient Requirements: No special requirements. Diatomite contains silica, which is absorbed into plant tissue and helps improve plant structure and resistance to pests / diseases
Usage notes: Prewash, as sediment may clog drippers. Many growers mix it with hydroton; this makes for improved air / water ratio. Also acts as a good killer of soil dwelling pests.

Sure To Grow

What is it? Recycled polyethylene terepthalate (PET) fibers
Where does it come from? North Carolina (USA)
How much? $60 (9 6”x6” blocks + 3 slabs)
Reusable? Not recommended by the manufacturer
pH: Neutral
CEC: Low
AFP: Medium-High
WHC: High – can hold up to 82% of its total volume when saturated
Pros: Sterile, lightweight, contains no residual particulates, recyclable
Cons: Larger plants will need extra support (i.e., staking / screening)
Irrigation: Top-feed, drip (except waterfarm systems), ebb/flow, DWC, NFT, aeroponics
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: STG comes in starter cubes, grow blocks, loose-fill cubes, flock, net pot inserts, capillary mats, and starter tray mats.

Rockwool

What is it? Heated basalt rock spun into a fibrous, lightweight material
Where does it come from? Mainly Europe
How much? $80 (9 4”x4” blocks + 3 slabs)
Reusable? No
pH: 8.0
CEC: Low
AFP: Medium
WHC: High
Pros: Lightweight, sterile, recyclable
Cons: Skin irritant, needs pre-treating before use.
Irrigation: Manual top-fed, ebb/flow, drip, DWC, NFT
Nutrient Requirements: Inert medium; requires pre-soaking, suits most hydroponic nutrient solutions.
Usage notes: Presoak with a water and pH Down solution of no less than 5.5 pH. After soaking, allow to drain and irrigate with a suitable nutrient solution before planting. Rockwool comes in starter cubes, plugs, blocks, slabs, mats, and loose-fill (absorbent or repellent granulate).

Clay Pebbles

What is it? Heat-expanded, round-shaped clay pebbles of mixed sizes (8-16mm most commonly used)
Where does it come from? Worldwide, mainly Europe
How much? $70 (100 liters)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High
WHC: Low
Pros: Difficult to over-water, maintains an excellent air to water ratio when irrigated correctly.
Cons: Bulky, nutrient precipitation on outer surface is common, needs washing before use
Irrigation: ebb/flow, drip, DWC, aeroponics
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Spills can be messy. Wash thoroughly before use to remove the small clay particles, this messy sediment may clog pumps and drippers.

Growstones

What is it? Porous rocks made from recycled glass beverage containers received from either the landfill or another source collecting and processing waste glass.
Where does it come from? Santa Fe, NM (USA)
How much? $80 (3.75 cu. ft.)
Reusable? Yes
pH: Neutral
CEC: Low
AFP: High
WHC: Medium-low
Pros: Lightweight; 35% water-holding capacity while maintaining an 85% air-filled porosity; capillary action up to 6″ (15 cm).
Cons: Bulky, needs frequent irrigations.
Irrigation: ebb/flow, DWC, aeroponics.
Nutrient Requirements: Inert medium, suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use to remove small particles. Ideal for using neat or for mixing into coco coir, peat and other growing media.

Peat

What is it? A naturally occuring deposit of partially decomposed vegetation, mainly mosses.
Where does it come from? Peat forms in wetland areas of North America, Ireland, Russia and Northern Europe
How much? Varies
Reusable? Yes
pH: 3.4 to 4.8
CEC: Medium – High
AFP: Medium
WHC: Medium-high
Pros: Readily available,supports beneficials, excellent at holding nutrients and has a good air to water ratio.
Cons: Limited natural resource, extaraction is harmful to the environment, does not re-wet well if left to dry out, naturally acidic.
Irrigation: Manual top-fed, drip
Nutrient Requirements: ‘Soil’ specific nutrients are recommended.
Usage notes: Peat is found in many grow stores in pre-mixed bags or bales. It usually has perlite added for improved drainage, a wetting agent for good re-wetting, and dolomite lime to raise the pH.

SteadyGROW

What is it? Phenolic resin and air
Where does it come from? USA and Canada, out of materials from India
How much? $41 (9 4″x4″ blocks and 3 slabs)
Reusable? Not recommended by manufacturer
pH: 6.0
CEC: Low-medium
AFP: Medium
WHC: High
Pros: No algae growth, sterile
Cons: Reports of phenolic resin’s carcinogenicity by NTP, IARC, and OSHA
Irrigation: Manual top-fed, ebb/flow, DWC, and NFT
Nutrient Requirements: inert medium, suits most hydroponic nutrient solutions.

Usage notes: Comes in two varieties: SteadyGroPro (low water retention) and SteadyGroPro H+ (high water retention)

Water (DWC, NFT)

What is it? Although pebbles may be used to anchor the stem, the plant’s bare roots are in direct contact with an oxygen-rich nutrient solution.
Where does it come from? Good question. Obtain a water analysis.
How much? 0.1 cent per liter for domestic volumes, and 0.03 cents per liter for industrial volumes.
Reusable? Yes (in recalculating systems)
pH: varies; distilled water is 7.0 pH
CEC: N/A
AFP: % of dissolved O2 increases as temperature drops
WHC: N/A
Pros: Readily-available, roots love it when properly aerated and at the correct temperature (64-70F)
Cons: Poor buffering capacity, pH-fickle, may harbor pathogens
Irrigation: DWC, NFT
Nutrient Requirements: inert medium, suits most hydroponic nutrient solutions.
Usage notes: Requires constant aeration to maintain dissolved oxygen levels necessary for healthy roots.

Sand

What is it? a naturally occurring granular material composed of finely divided rock and mineral particles
Where does it come from? Varies
How much? $10-$15 (3 cu/ ft.)
Reusable? Yes
pH: Varies according to its mineral content
CEC: Low
AFP: Low
WHC: Medium
Pros: Cheap, excellent drainage
Cons: heavy, must be irrigated on a schedule for optimal results
Irrigation: manual top-fed, ebb/flow, drip
Nutrient Requirements: Most are inert, some may contain lime. Suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use. Check and correct pH of runoff prior to planting.

Sawdust

What is it? Wood shavings
Where does it come from? Varies, usually as the byproduct of sawmills and retail hardware stores
How much? If you ask nicely, they may give it to you for free!
Reusable? Not recommended
pH: 6.1
CEC: Medium
AFP: Medium-High
WHC: Medium
Pros: Inexpensive, lightweight, biodegradable, harbors beneficials
Cons: pH-fickle, needs frequent irrigations
Irrigation: Manual top-fed, ebb/flow, DWC
Nutrient Requirements: Diligent pH monitoring and adjusting is of the essence. Suits most hydroponic nutrient solutions.
Usage notes: Best used for cycle crops and annuals.

Gravel

What is it? Any loose rock that is larger than 2 mm (0.079 in) in its smallest dimension (about 1/12 of an inch) and no more than 64 mm (2.5 in).
Where does it come from? Worldwide, mostly USA
How much? $12-$15 (3 cu. ft.)
Reusable? Yes
pH: neutral
CEC: Low
AFP: Medium-high
WHC: Low
Pros: Inexpensive, easily-available
Cons: Heavy weight, bulky
Irrigation: Ebb/flow, DWC, Aeroponics
Nutrient Requirements: Mostly inert medium, may contain soluble minerals. Suits most hydroponic nutrient solutions.
Usage notes: Wash thoroughly before use. Gravel is an old school hydroponic substrate.

by Eliab Lozada

Rockwool is a mainstay of commercial hydroponic growers – and for good reason. It takes up a minimal footprint and, when used correctly, yields like crazy. We asked Dr Lynette Morgan, a world authority on hydroponic vegetable production, to give us some expert advice on growing tomatoes in rockwool. There’s LOTS to be learned here as Dr Morgan takes us through how to develop irrigation strategies for your particular growing environment.

Rockwool, also known as stone wool or mineral wool, is the most widely used substrate for the commercial production of hydroponic tomatoes. It is also a great tool for smaller growers who can benefit just as much from its use in a range of different systems and situations. While rockwool is relatively easy to set up and use, it does require some monitoring and irrigation adjustment to make the best of its ability to hold high levels of moisture and aeration at the same time.

Rockwool originally started as a thermal insulation material in the construction industry: its lightweight but highly aerated nature helps keep heat in buildings, while being easy to handle, cut and install. However, towards the end of the 1960s, trials were carried out in Denmark to test the possibility of using stone wool as a substrate for plants. Things went well and since then rockwool as a growing media has seen some continuing development of the substrate and the tools used to manage it.

Rockwool comes in a range of sizes from propagation cubes to large slabs and even a granulated product.

Rockwool is manufactured by melting basaltic rock and spinning this molten mix into thin fibers which are then cooled by a stream of air. Although rockwool is a man-made substrate it is essentially made from rock and considered by many to be a natural product. Grodan dominates the rockwool market world-wide and is the most common brand used by large and small hydroponic growers alike. Grodan rockwool is highly advanced and is not a single product – growers can select from a number of different Grodan rockwool types such as `Grotop Master,’ `Grotop Master dry,’ and `Grotop Expert,’ all of which have slightly different properties and uses. `Grotop Master Dry,’ for example, maintains a slightly drier root zone and is used by tomato growers to steer crops away from overly vegetative growth. `Grodan Classic’ is used for multi-year use, while `Grotop Expert’ is designed for ultra quick root growth and development. Along with these product differences, rockwool of many brands comes in a huge range of sizes from tiny propagation plugs for seeds to larger cubes for cuttings, mega sized cubes for large plants, a wide range of slab sizes, and as a granulated product as well.

Setting up to grow with rockwool

1. Sit the rockwool down

Whether you are using the standard rockwool growing slabs, large cubes, or even pots of granulated rockwool, basic preparation is important. Slabs and cubes in particular need to be on a flat, even surface as any indentations will cause the material to sink and create pockets of unwanted moisture. Next, realizing that nutrient solution will be draining from holes cut in the slab’s plastic wrapper or from the base of cubes, some consideration for drainage of this solution away from the slab is important. There is no point in having well placed and made drainage holes if the solution can’t be channeled away from the slab and the material ends up sitting in a pool of stagnant waste nutrient. Many small hydroponic systems on the market these days designed for use with rockwool have trays and channels designed to do just this and these are a good choice for inexperienced growers.

2. Settle the rockwool in

Rockwool, whether it is slabs, small propagation blocks, or large growing cubes, needs to be prepared correctly by fully wetting the substrate before use. Some growers like to adjust the pH of their water to 5.5 before wetting up rockwool, but generally for small systems it’s not necessary with good quality brands (unless you have a very `hard’ water supply in which case acidification of the water before making up any nutrients would be a good idea). The rockwool should be fully saturated so that all of the material is wetted and then left to drain. Some growers pour water into the rockwool slab before the drainage holes have been cut to make sure everything has had a good drenching, while others just pour water on or run the irrigation long enough for saturation to take place.

3. Remember the holes

Rockwool slabs need drainage – holes or slits should be cut in the plastic sleeve the material comes in. Several cuts are required along the base of the slab. Granulated rockwool should be placed into containers or pots with plenty of drainage holes in the base.

4. Irrigation programs

The most common way of applying nutrient to rockwool slabs or large blocks is with the use of dippers. A simple drip irrigation system should use a dripper with a capacity of 2 litres/hour, with one dripper per plant. Because a standard rockwool slab may hold four tomato plants, four drippers per slab are required, which also means that if any one dripper becomes clogged, the entire slab will still be getting enough irrigation until the problem is fixed.

Developing an Irrigation Strategy for Rockwool – The Moisture Gradient

Rockwool is the most widely used substrate for hydroponic tomato production.

The irrigation program for any hydroponic plant is vital for successful growth, development and optimal yields. The most common problem experienced by smaller or new growers is over watering, and usually the grower is totally unaware that it is their irrigation program causing problems with plant growth. Flushing vast amounts of nutrient solution through the root zone in a substrate-based system often equates to plant murder – more is not necessarily better when it comes to nutrient application. This type of mistake is easy to make. After all, many new growers get enthused about hydroponics after seeing a well-run NFT or other solution culture system and assume that plants are more than happy to grow and thrive in a flooded root zone environment. However, solution culture and substrate systems are completely different and need to be managed in different ways for the plants to get the optimal root zone conditions they need. In NFT the roots should never be flooded: they sit in a very thin film of nutrient flow (2-3 mm or about 0.1″ deep), hence the roots have moisture at the base of the root system, but many of the other roots are sitting up in the moist air, accessing all the oxygen they need without being submerged. In a rockwool slab the plants are in a similar situation – at the base of the slab there is plentiful moisture, usually at media saturation levels, while in the upper layers of the rockwool slab the roots are in drier conditions and hence have access to plenty of aeration and oxygen for root uptake and respiration. It is this moisture gradient from the top to the bottom of the rockwool material that makes it such a good substrate. At the same time, growers who are not aware of this property can make the mistake of thinking the rockwool is too dry on the surface and over-irrigate their plants despite having plenty of nutrient solution being held deep down in the root system. Rockwool growing media, when being irrigated correctly, should not sit in a pool of nutrient and be completely saturated from top to bottom like a sponge. It is essential that the rockwool is allowed to completely drain so that excess nutrient leaves the slab or cube under the pull of gravity after being applied– in doing so, fresh air is drawn into the top layers of the material, providing fresh oxygenation for the root zone. By allowing the rockwool material to drain freely, over-watering becomes more difficult, although vast amounts of nutrient drainage from the base of rockwool slabs or cubes is not an ideal situation either.

Setting up an Irrigation Program

Obviously the amount of nutrient required is going to depend on factors such as the size of the plant, the growing conditions, light, temperature and, in particular, humidity, which drives plant transpiration and water uptake. So the irrigation program is going to change as the plants develop. Also an irrigation program needs to be developed and adjusted by each grower for their particular system, environment, and set up and this has to be monitored and adjusted as required. Just following guidelines for the amount of nutrient to apply at certain times will eventually lead to over or under-watering, as each plant and situation is different when it comes to nutrient and water requirements.

Commercial hydroponic rockwool growers have some good tools for fine-tuning their irrigation. The Grodan water content meter allows growers to measure the water content, EC and temperature in the rockwool slab root zone using hand-held meters or a continuous monitoring system hooked up to the computerized irrigation program. However, these sorts of high-tech tools are not often used by smaller growers and a successful irrigation strategy can be put together with just observation, some innovation, and a little time.

Remember the Moisture Gradient

Rockwool propagation cubes and slabs are designed to be used together to minimize root disturbance. Excellent moisture holding capacity and good aeration of the root zone are features of rockwool substrates.

Irrigation of rockwool is a little different to other solid substrates because of the way the material is manufactured to have just the right degree of moisture gradient, and because it does give quite a limited root zone for plants that eventually grow fairly large. For this reason, rockwool is best irrigated with short, frequent applications of nutrient, with just enough at each irrigation for the rockwool to reach ‘field capacity’. Field capacity is a term that means the substrate has drained fully but is still holding a good level of moisture for the plant roots to access until the next irrigation. At each irrigation, there should be some drainage from the rockwool material. However, this doesn’t need to be excessive. Even in closed systems where the drainage solution is being collected and reused, it pays not to over-water and not to run the irrigation continuously. Having around 10-15% of the nutrient solution fed to the plants, drain from the slab at each irrigation is considered to be optimal. This amount of drainage of solution flushes fresh nutrient solution right through the slab without too much wastage and usually keeps the EC in the slab fairly stable.

When rockwool is irrigated and allowed to drain naturally, it will then contain 80% nutrient solution, 15% air pore space and 5% rockwool fibers. A typical rockwool tomato growing slab actually holds around four gallons (about 15 liters) of nutrient solution immediately after irrigation, despite the drainage holes allowing free drainage of excess solution. Four gallons is a good reserve of moisture for four plants, so drying down to wilting point could take a long period of time for small plants.

How much solution should be given at each irrigation?

Having a drainage collection tray or channel under each slab allows growers to see how much drainage they are getting after each irrigation (even if this has to be poured off and measured in a jug) and the irrigation program can be increased or decreased to keep this at the 10-15% level. By doing this, the amount of solution to be given at each irrigation can be worked through and adjusted as the plants grow. Keep cutting back the irrigation amount until only 10-15% of the solution volume applied drains from the slab, and then the amount of irrigation has been fully adjusted for.

How often should nutrient be applied?

Rockwool needs small frequent irrigations, particularly under hot or low humidity conditions when the plants are taking up a lot of water. However, the frequency of irrigation can be as low as once per day (or every other day) for small plants under cool conditions, to over 10 times a day for large plants in a hot or dry environment. It can be hard to judge just how much moisture the rockwool material may be holding at any one time to determine when to irrigate. Smaller propagation blocks and even larger cubes can be gently picked up – the weight will soon tell you if the cube is saturated (it will be comparatively heavy and moisture will drip from the wet base), or whether it has dried out considerably, in which case it will feel very light (compare an unused dry cube to one in use). Rockwool is an unusual material in that, even when the slab has lost 50% of its moisture to plant uptake, the plants are still able to very easily keep extracting water until the slab is almost completely dry – so plants in rockwool can’t get water stressed until the rockwool is almost completely dry, by which time the cube or slab has become much lighter in weight. For granulated rockwool in pots or containers, a similar method can be used, either by gently lifting the pot to see what the weight might be (a light pot is a dry pot) or by a light tap or kick: if the pot moves, the rockwool has become quite light and potentially too dry.

Another method to try and gauge the moisture status of the rockwool and how often to irrigate is to carefully remove a small piece of the wrapper plastic and examine the moisture gradient of the slab from top to bottom. Like all growing media, moisture in rockwool can be gauged manually. Lightly touching or pressing the rockwool at the base of the slab will soon determine if there is still a good level of nutrient held in the base of the slab or whether it has become too dry. The top and middle layers of the slab should always appear drier than the base where the reservoir of moisture is naturally held, so only the base of the slab should be checked. Even if the top of the slab appears to be dry, this is not important as the moisture gradient has been designed to give these sorts of root zone conditions – only ensure the base of the slab has sufficient moisture.

This process of working out how much moisture is still in the rockwool material is not something that needs to be done for long. Growers will soon become quite skilled at working out their frequency and amount of irrigation for each stage of plant growth and may only need to do this for their first crop provided growing conditions remain stable. Other times when it might be important to have a quick check of the amount of solution drainage or amount of moisture in the slab is when conditions suddenly change – addition of more grow lamps, sudden changes in temperature or humidity, or rapid growth spurts can all change the irrigation requirements of the plants.

Generally, good brands of rockwool are quite forgiving compared to other substrates – the material is naturally well aerated and doesn’t suffer the compaction issues that some substrates do during the life of the crop. It does hold high levels of moisture, so the chance of drying out is not as severe as it might be with other substrates and being sterile gives young plants, seedlings and cuttings an advantage as well. The irrigation program and water holding capacity of the substrate depends on the fiber density and arrangement, which can differ from brand to brand.

More Advanced Irrigation Practices

With tomatoes and similar crops, growers have the option of using the EC and moisture content of the rockwool slab to help ’steer’ the plants into either more vegetative or ‘generative/reproductive’ growth, depending on what is required. Drying the slab back between irrigations and allowing the EC in the root zone to increase pushes tomato plants into a more generative or reproductive state with less leaf growth and more assimilate being directed into the fruit. A higher level of moisture maintained in the rockwool and a lower EC pushes the plants towards more lush vegetative growth. Skillful growers use these techniques to direct their crop and control leaf, flower and fruit growth at different times, and rockwool is a great substrate for this sort of control via the root zone.

Other Rockwool Tips

EC Levels and Management

Checking the EC in the root zone is important with rockwool just as it is with any media. The EC of the nutrient solution in the growing substrate changes as plants extract different ratios of water and nutrients from the root zone. The EC in the drainage solution coming from the base of the rockwool cubes or slabs is the best indication of the EC the plants are actually experiencing in the root zone. As a general rule, the EC in the drainage solution should be the same as or only slightly higher than that applied to the plants in the feed solution. If the EC is becoming much higher in the drainage than what was fed to the plants, then the EC in the feed solution should be dropped back – this is common under hot growing conditions when the plants might be taking up far more water than nutrients, hence concentrating the nutrient solution.

Rockwool Reuse

Rockwool for tomato crops can be reused – some commercial growers get many successive crops from rockwool slabs by steaming these after the plants have been removed and then replanting. Smaller growers can also do this – a few slabs can be heat treated by pouring hot water through them. Solarization is also possible, as is using chemical disinfectants, although care should be taken to rinse the rockwool well with plenty of water after using these. Commercial Grodan users have the option of the Grodan recycling service, which picks up the used slabs and recycles them into new product. However, smaller growers with just a few slabs of used rockwool can recycle the material by shredding it and reusing it as a growing media, as a component of potting mixes, or by incorporating it into outside soils and gardens.

Real World Rockwool Q&A

Q: What pH should I adjust the nutrient solution to and how do I monitor and adjust accordingly? For instance, keeping the tank pH at 5.8 and the run-off at 6.0 is perfect, but what happens if the pH starts to come back higher or lower than expected? What could / does this mean? And what should be done to correct it? How much should a grower raise or lower the pH of the tank with pH adjusters – when does a situation become ‘too extreme’ to use pH adjusters?

A: There are many factors that affect pH in the nutrient: some are normal like plant uptake and nutrient formulation salts (NH4 in particular), and some are not so good, like root disease. Water plays a big role and can range from very hard to very soft and hence needs to be handled differently depending on what a specific grower is dealing with. Chemicals for pH adjustment are also a huge topic! The nutrient solution pH is usually optimal at around 5.8 – 6.0 for commercial tomatoes; however, for small systems pH in the range of 5.5 – 6.8 is usually fine and having tight control at 5.8 is not necessary. The main problem with pH is with growers who might have a `hard’ water source, which is highly alkaline. In that case, acidifying the water with acid (nitric or phosphoric) before making up any nutrient will give better and longer term control of pH swings (in any growing media). pH should not need to be raised in most situations unless the water supply is very acid: in that case, potassium hydroxide should be used.

Q: I understand that rockwool can be prone to salt build-up if you don’t know what you’re doing like the commercial guys. Most hobby rockwool growers I have talked to flush either one day a week, throughout the whole grow and bloom cycle, or when they dump the res. (They will commonly give their plants 24 hours of either very low nutrient solution (if so, what EC?) or pure water, or even pure water with a product like GH Flora Kleen. What do you think of these flushing techniques? Do you have any better advice?

A: Rockwool is actually one of the better media for preventing salt build up as it tends to be drip irrigated from above and not bottom watered like with ebb and flow. Flushing is another subject that really needs a whole article to cover the theory, practice and problems with it. Flushing with straight water after a plant has been sitting at normal or high EC is not recommended: it causes the plant cells to suddenly take up huge volumes of water (because the osmotic pressure has been dropped in the root zone). This can cause cells to burst and create major physiological problems – splitting of tomato fruit is one common one; many other fruits and vegetables do the same. Even low strength nutrient can do this. Any changes in EC in the root zone should be done slowly (i.e over days), so a gradual dropping back of the EC over a few days should be done rather than flushing with water. Or better still, don’t let EC build up in the first place!

Q: What is the disadvantage of watering rockwool for a minute and getting 50% run-off in a closed system with adequate drainage, as opposed to watering for a minute and getting, say, 15% runoff? If you are only achieving 15% run off, is it not the case that the rockwool is already fully saturated and any additional runoff will just wash out the excess salts more thoroughly? In short, how difficult is it to over-water rockwool? I also can’t see what the problem would be for the plant if more run-off was created unless, of course, you were irrigating for several minutes to achieve this much run off, but even then surely the plant won’t feel any effect having its roots flooded for, say, 10 minutes, then allowed to drain freely?

A: Rockwool is a media which has been specifically designed for commercial growers who aim to have the recommended 10-15% run-off with the slabs spending as little time as possible at saturation levels – when doing this, the structure of the rockwool has been manufactured so that the root zone will remain at the correct moisture status which is why it is recommended. Also, with rockwool systems, the feed nutrient should be applied so that ‘excess salts’ don’t occur and therefore don’t need continual flushing. If the EC is getting high in the drainage solution, drop it back in the feed solution and/or increase the frequency of short irrigations. Rockwool, like any media, can be over-watered if flooded and is best kept below the saturation level for balanced growth.

Q. What’s the scientific explanation behind the influence that irrigation strategies have (or, to be more precise, the levels of moisture in the root zone) on generative / vegetative growth? Is this peculiar to tomatoes or is it applicable to other species?

A. Crop ’steering’ as it’s called is a technique used by commercial growers to manipulate the natural growth pattern of the plant. It’s widely used by skilled growers of tomato crops, but also on capsicum and many other plants as well. It’s quite a complex topic as there are a number of tools a grower can use in a controlled environment to direct the growth of the crop – commercial growers will use a combination of DIFs (day/night temperature differentials), EC, CO2, moisture control in the root zone and directional heating (i.e. directing heat towards the fruit or tops of the plants) to manipulate the growth of the plant. Different techniques force the plant to send the assimilate produced in the leaves into flowers/fruits when required or direct the plant back to some more vegetative growth if that was what was required. Various temperature techniques are sometimes used to keep seedlings or older plants as short and compact as possible (i.e. prevent stem elongation) and to get the plant to hold back on the production of overly large, succulent leaves. Commercial tomato growers use tools such as measurement of stem diameter to determine if their plants are getting overly vegetative or too generative at certain times of the year. The basic scientific explanation of why this works is that when a flowing plant encounters ’stressful’ conditions such a drying back of the root zone, high EC, high light and temperatures, it triggers a response – the plant wants to hurry up and flower, and to set seed to make sure it reproduces before the harsh conditions can kill it. We sometimes see this effect on lettuces which, under high light, temperature and moisture stress, can flower (or bolt) while the plant is still only a seedling and far from maturity. A plant with plenty of moisture under no particular stress is happy to go on producing a lot of large leaves with no hurry to set fruit and seed, which is great for vegetative crops such as lettuce but not so much with fruiting crops like tomatoes and capsicums. The ‘controlled stress’ commercial growers use to direct plants into more generative growth is often via the root zone because with Grodan rockwool very precise control of moisture content in the substrate can be controlled – particularly with the use of the Grodan moisture meter. And in hydroponics, control over EC is also fairly easy and precise. For this reason, Grodan Rockwool has different products for growers who might need to steer their crops towards more generative growth by having a drier root zone. It makes it much easier for the grower to then restrict irrigation and moisture levels in the root zone to steer the plants towards more generative growth and generally the technique is very effective. However, commercial growers use high tech tools likes moisture meters linked to their computerized irrigation program so that the crop is not at risk of being damaged by delaying irrigation to long. Smaller growers can certainly use similar techniques and allow the rockwool to run a little drier between irrigations and keep their nutrient run off to an absolute minimum if their plants are getting a bit too vegetative. Running a lot of nutrient through the rockwool on a frequent basis means the slabs or media are at saturation for much longer, and that favours vegetative growth (although we should also remember a lot of other factors, such as the growing environment, play in a role in the vegetative/generative balance as well).

Dr Lynette Morgan holds a B.Hort.Tech(Hons) degree and a PhD in hydroponic greenhouse production from Massey University in New Zealand. Her PhD thesis focused on hydroponic tomato production in both NFT and media systems and improvement of fruit quality aspects. Now a partner in SUNTEC International Hydroponic Consultants, Lynette is involved in many aspects of hydroponic production, including remote and on-site consultancy services for new and existing commercial greenhouse growers worldwide as well as research trials and product development for manufacturers of hydroponic products. Lynette is also the author of 5 hydroponic technical books: Hydroponic Lettuce Production, Hydroponic Capsicum Production, Fresh Culinary Herb Production, Hydroponic Strawberry Production and her latest release, Hydroponic Tomato Crop Production.

WORDS: Heather Walker

Germination Basics

To go from seed to seedling, tomato plants need a moist growing medium, light, and warmth. I grow seedlings in my own organic potting mix of peat moss, vermiculite (some growers prefer perlite), green sand, bone meal, and organic soybean meal. You can add some aged compost too, but weeds may take over your seedlings if the compost wasn’t hot enough to kill the weed seeds. I soak the mix in a wheelbarrow with warm tap water (we’re on a well, so no chlorine worries here) then run the hose to add water until I can squeeze the soil mix and water runs out. I fill 4-inch pots with the wet mix, then plant one seed in the center of each pot and label it: name, date planted, open pollinated or hybrid.

I like to start my tomato seeds in 4-inch pots on the windowsill in my living room, directly above a baseboard heater: the additional bottom heat gives them that extra encouragement. This summer was the first year I tried heat mats, and I definitely noticed a shorter time to germination with those bad boys.

To know when to water, dig down an inch or so at the edge of the pot, and if it’s still moist then don’t bother watering. If it starts to look dry, soak the pot a few times with room-temperature water.

Eager tomato seedlings on a heat mat.

Seedling Mix

2 parts by volume sieved garden soil
1 part by volume sieved sphagnum moss
Add to each cubic foot (5 gallons) of mix:
1 cup agricultural lime or dolomite lime
1 cup cottonseed meal or soybean meal
1 pint soft rock phosphate or 1 cup steamed bone meal
1 cup kelp meal

From “Growing Vegetables West of the Cascades,” by Steve Solomon.

The Sprout

Once the sprout emerges with its first pair of leaves, it’s time for the tough love. If you spoil your tomatoes when they’re young, they will grow into leggy plants that will be ill-prepared for the real-world conditions in the outdoor garden. If you give your tomatoes lots of warmth when they aren’t getting a lot of sun or supplemental light, they can get “leggy,” growing tall with a spindly, weak stem. This is particularly important for growers in the Northern half of our continent, where the sun’s strength and height in the sky in March/April may not offer enough light. The plant, receiving lots of warmth but not much light, reacts as if it’s being shaded by other competing plants: as a result, it grows fast and tall in an attempt to access the sun and out-compete the other plants that it thinks are crowding it.

These leggy tomato seedlings were exposed to too much warmth with not enough light, which encouraged them to stretch: the stems are thin and weak as a result. Weak plants are more susceptible to disease, drought, and pests. Photo: Greg Wagoner.

To prevent leggy tomatoes and encourage stocky, strong growth, narrow the gap between the light and heat the plant is receiving. To do this, steel your heart and move every tomato with leaves into an unheated greenhouse during the day, unless it’s unusually cold. The greenhouse protects the young plants from the wind, cold, and rain/snow, but exposes them to cooler temperatures than in the house, and more sunlight through the poly-plastic roof and walls: they will receive more light and less heat than on the windowsill or heat mat. Bring them in at night until you’re confident that the temperature won’t drop below 50°F (10°C), which can compromise a tomato plant’s development or kill it.

Ideal Tomato Growing Temperatures

Day: 65-70°F (18-21°C)
Night: 50-60°F (10-16°C)

It’s also important to expose your tomato seedlings to air movement from this point forward. Fans, ventilation, an open window, or even your hand brushing their tops a few times each day will encourage more stocky growth and prepare the plants for the realities of wind. Novice growers often leave the clear dome on their plant starts for far too long. Don’t be an overprotective tomato parent!

Transplanting

It’s very likely that your tomato plants will outgrow their starter pots before it’s safe to plant them outside. In fact, this is preferable: the more times you can transplant your tomatoes into larger pots, the better. Why? Because every time you re-pot a tomato plant, you bury it up to its “neck” (just below its top set of leaves), or as much of the plant as you can fit under the soil. The tomato will then send out roots from the newly-buried stem, creating a more well-developed root system. And a strong root system leads to a healthier, more productive plant! Transplanting in this way also helps control the ultimate size of your plant once it’s ready to go into the garden: it’s far easier to plant a foot of stem and foliage with 8-inches of well-formed roots than a 2 foot spindly monster that will snap in half if you look at it funny.

So once your tomato outgrows its four-inch pot, bury the plant up to its neck in a gallon pot of soil, with the top set of leaves above. If you start your tomatoes in 1-2″ cell trays, transplant them into 4-inch pots when they’re ready for more room, then eventually into the gallon pots. And once a tomato outgrows its gallon pot, it’s probably time to plant it outside.

Transplanting a tomato plant from a small pot to a larger pot: bury the plant up to its neck, leaving the top set of leaves above the soil.

Hardening Off

It’s a blue-skied, warm, sunny day: you’re ready to unpack those shorts and plant out your tomatoes! But hold on. It’s crucial that you gradually prepare your tomato plants for outdoor conditions, rather than abruptly moving them from their cozy, sheltered existence into the cold, hard world.

Plants must be “hardened off” for a week or so by gradually exposing them to less-hospitable conditions for increasingly longer lengths of time each day. My plants progress from their windowsill nursery, to the unheated greenhouse in the daytime, to the unheated greenhouse 24 hours/day. I’ll start leaving the greenhouse door open, then setting them outside for the daylight hours. It’s best to put them out on a cloudy or partly cloudy day, as a full day of direct, hot sun can be hard on a plant. Plants can sunburn too! Eventually there will be a warm night and I’ll leave them outdoors. If frost is in the forecast, or a storm, I’ll bring them under shelter until it’s clear again. Eventually the plants will become more hardy, and spring will really be here, and around late May to early June I’ll be able to risk planting them out.

Into the Garden

This transplanting technique from pot to outdoor garden minimizes transplant shock and encourages strong root development.

Rather than digging a hole and planting the rootball at the bottom, as when re-potting, lie each tomato in its place horizontally on the outdoor garden bed, then bury it in soil — again, up to the top set of leaves. Be careful to support the stem, to avoid snapping it. Carefully pat down the dirt to ensure plant/soil contact, then water the whole plant thoroughly. The top of the tomato plant will eventually turn up toward the sun and grow into a surprisingly strong stem, supported by the amazing root system you’ve helped it develop.

It might seem easier to dig a trench and lie the plant in it, to keep your garden bed nice and flat, but if you do this you risk exposing the plant to the chillier soil underneath that sun-warmed top layer. Tomato plants may turn blue/purple-ish as a result — a sign of transplant shock. They will take longer to recover, which may affect the time or quality of harvest.

Have your own tomato-starting secrets to share? Tell us about it below…

Gel2Root from SupaPlants come in packs of 6, although some retailers will sell them individually. Each clear plastic cup contains Gel2Root rooting gel and a foil top to contain the medium’s moisture.

You pierce the foil, insert your cutting, and walk away. Some days/weeks later, voila, a rooted clone. Simple, no? Pretty close.

Any new cloning methods that I test will not be used with easy-to-clone or fast-to-thrive plants. I see no need to switch methods unless I’m having problems. This is where I leveraged the Gel2Root cups.

I chose 2 difficult-to-clone plants: a strawberry variety and Cuban mint (mojito-lovers rejoice!). With my GH RapidRooters, the best cuttings from the Cuban mint died before they could thrive. Failing Cuban mint turns black quickly. Easy indicator.

Of the strawberries, only 1 of 3 rooted. However, it rooted well. So well, in fact, that the roots almost sucked dry the canopy before I noticed that it was time to transplant it.

The real benefit of this medium is that it is maintenance-free. No need to water a block or plug. No need to use rooting hormone or rooting powder. In fact, using these additives stunts the effectiveness of the gel.

In the case of Gel2Root, the mint thrived in the medium and rooted after 8 days. The strawberry took 3 weeks. In both cases, I needed to do nothing else. I kept both plants inside my humidity dome, atop my seedling tray.

Words of advice when using this medium:

• Make the foil insertion hole as small as you can to avoid medium evaporation. If the hole allows too much evaporation of the medium, your cutting will be air-exposed and not root. Of the 6 cuttings I tested, this occurred in 1 of them.
• Don’t insert more than 2 cuttings per gel cup. While you can attempt 3 (as per instructions), each cutting’s canopy may overshadow the others.

I won’t use Gel2Root for all of my cuttings. However, when my main clone methods generate no results or if I need maintenance-free cloning, I will roll with the Gel.

Embrace your Clear Side!
- Curtis

Please note: blog posts are the opinions of independent growers, and do not necessarily reflect the opinions or experiences of Urban Garden Magazine or its affiliates.

Over in Europe, NFT has been the preferred hydroponic method among hobby growers for many years. Now finally, it seems, the word is beginning to spread to hobby growers over on this side of the Atlantic. But what’s the real deal with NFT? Does it truly offer all these promised benefits to hobby growers without any catches or compromises? Is it just suitable for salad crops or can it deliver when applied to heavy, fruit-laden annuals like tomatoes and cucumbers?

Our main man with a high yielding plan, Everest Fernandez, takes a first look at NFT Gro-Tanks and shares some of his hands-on experience.

WORDS: Everest Fernandez

NFT 101

Ok, don’t be shy. Raise your hand if you don’t know what the hell NFT is. No worries! We’ve all been there, and that’s what I’m here for I guess …

NFT stands for Nutrient Film Technique. It refers to a general method of growing plants hydroponically. In NFT nutrients are added to water just like any other hydroponics system and this solution is contained in a tank. Plants sit on a grow tray above the tank and the nutrient solution is pumped up to the tray. The tray is positioned so that it lies on a slight gradient. The nutrient solution flows constantly over the roots feeding them all the nutrients and water they need. Any nutrient solution that is not up taken simply flows back through a hole into the tank where it is re-circulated.

But What Are The Plants Growing In?

The roots of your plants are constantly bathed in an oxygen-rich nutrient solution. It forms a thin ‘film’ about 0.03 to 0.1 inches in depth. A thin layer of capillary matting called “spreader mat” is first placed over the tray. This helps to spread the flow of the nutrient solution evenly over the entire surface of the grow tray. We all know that roots hate light. That’s why they tend to stay under the ground in nature! Fortunately the root zone is protected with a piece of Correx (kind of like a cross between cardboard and plastic). Small holes are cut into the Correx, just big enough for the base of the plants to fit through. This also helps to prevent algae growth in the root zone or nutrient solution.

Cucumbers grown in an NFT system.

The thin nutrient film not only provides your plants with all the water and nutrients they need, it also gives them access to loads of oxygen – essential to maintain key metabolic processes in the root zone that regulate how efficiently your plants can feed. This is a key feature of NFT. There are always some parts of the root zone that have more access to oxygen than others – simply because they are higher up: these parts of the root zone help to supply lower parts with all the oxygen they require. This is just one aspect of plant physiology that NFT growers exploit to their advantage. When plants have access to all this water, nutrient and oxygen simultaneously the growth rates can verge on being scary.

Gro-Tanks vs. Gullies

NFT Gro-Tanks can accommodate a far wider root system than the NFT ‘gullies’ you may have seen on commercial hydroponic farms (commonly used to grow basil and other leafy greens) making them ideal for plants that produce abundant root systems such as tomatoes.

Go With The Flow

NFT Gro-Tanks often come supplied as a complete kit for hobbyists – including the right sized pump. Solution flow is generally unimportant but should normally be between 1 to 3 pints (400 ml and 1500ml) per min. Channels should be sufficiently sloped, normally not less than 1:50 but may be much steeper if set-up allows, so that there is no “pooling” in the channels.

Plant Stability

What about heavy, fruit-bearing plants like tomatoes? Surely without any growth media, the plants are simply going to keel over due to their own weight, right? Amazingly, the plants form such a thick mat of roots underneath the Correx that they are very well supported. That’s not to say that some top heavy varieties won’t benefit from some net supports – but that’s often the case across the board when you grow plants near to their maximum capacity!

Propagation

NFT growers start their seedlings and cuttings off in the regular way, perhaps propagating in rockwool cubes or another inert media (e.g. net pot with clay balls.) Aeroponic cloning machines can also be used. Just as with any other hydroponics system, it’s really important to ensure that your seedlings or cuttings have a sufficiently developed root zone before transplanting them into an NFT grow tank. Don’t just wait for one or two roots to poke out. Aim for a mass of roots first! A great tip is to use an air-pruning tray (see UGM005, page 28) to generate a compact, dense root zone that’s bursting to break free!

Everest’s NFT Grow-Tank Tips

Here are some of my special tips learned the hard way:

1) If you are using rockwool starter cubes, ensure that the ridges at the bottom of the cube are in line with the nutrient flow, not perpendicular to it. Otherwise your nutrient flow will be impeded.

2) No growth media around the root zone means less insulation and less protection from extremes in temperature – so you need to have your garden’s environment dialed in. The temperature of your nutrient solution is also crucial – but this is no different than with other hydroponic applications. Try to keep your nutrient solution at around 65°F for high levels of dissolved oxygen and optimum nutrient uptake.

3) Plants grown indoors under lights will take up water at a greater rate than they take up nutrient. Over time the EC (CF) of the solution will rise. Regularly top up your tanks with water or 50% strength nutrient solution. Keep your top up nutrient solution in a separate barrel rather than using water straight from the tap.

4) Maintain the pH of your nutrient solution at around 5.8 – check regularly as it can rise as the plants feed.

5) As a general rule, drain your nutrient solution and replace with a fresh batch every 7 to 10 days for optimum yields. Obviously bigger tanks can get away with less frequent changes whereas bigger plants prefer more regular fresh nutrients. For more information on nutrient change-outs make sure you read ‘Maximizing The Nutrient Environment’ by Lawrence Brooke (UGM004,005,and 006).

6) Do not let any light leak into the root zone. Ensure the holes in the Correx cover are just big enough for your plants to fit through. Cover the bases of your plants to prevent green algae forming – especially important if using rockwool cubes.

7) Thoroughly clean your tanks in between crops with a soap solution and rinse thoroughly.

Wait until roots are showing out of your starter blocks before inserting them into your NFT system. This is absolutely crucial!

9) Use a half strength nutrient solution to start your plants off, moving to two thirds to full dosage rate (as detailed on the bottle) after the first nutrient solution change (about 7 – 10 days after planting).

10) Take the opportunity to observe your plants’ root growth directly by simply lifting up the Correx cover!

11) Make sure you completely remove plastic wrapping from rockwool cubes or remove pots if using soil or coco. This allows the roots to access more oxygen.

12) NFT is a bare rooted growing technique. All but the smallest of plants will need additional support, i.e. yoyo’s or pea netting.

13) Cut lengths of spreader mat long enough to allow an overhang of a few inches from the channel into the tank. No trickling water sounds!

14) Don’t crowd them! Plants grow incredibly fast in NFT Gro-Tanks – many growers are overwhelmed!

Think NFT – Think Sushi!

NFT constantly provides plants with the opportunity to feed rather than other methods which just provide several opportunities to feed. It’s a bit like sitting in one of those once-trendy sushi conveyor belt restaurants all day, every day. You, like your NFT plants, can take what they want, when they want it, rather than having to wait for their next feed. As a result, you and your plants are going to end up very happy and heavy!

Planting out and Irrigation

First, mark your planting sites with a marker on the Correx sheet. Do not position any plant too close to the pump. Make the holes just big enough. The aim of the game is to allow your cuttings or seedling access to the nutrient film without letting light in through gaps. Lay a single layer of spreader mat over the grow tray. Run your pump 24/7, day and night. There’s no need to work out irrigation cycles and frequencies. Your plants will simply absorb as much or as little nutrient as they require. This is perhaps one of the most appealing aspects of NFT. You should be able to see obvious root activity within 24 hours of planting out. Root axes grow into the nutrient film. Fine root hairs will also grow around the propagation media.

Incredible Root Development

One of the best aspects of NFT growing is the ability to peer at the huge mat of roots that quickly develops underneath the Correx cover. It’s easy to assess the health of your plants – just look for a thick mat of white roots! Watch that the roots don’t get carried away and grow into the pump. (Unlikely, but it does happen.) Clean-up in between harvests is a lot less hassle than with media-based growing methods too, mainly because there is so little media to deal with. This makes NFT Gro-Tanks a great choice for the hobby grower who doesn’t want to endure the regular hassle, expense (and back ache!) of carrying endless bags of soil, coco or clay pebbles.

The Verdict?

Once I tried NFT I immediately saw the benefits, despite grossly overcrowding my Gro-Tanks with waaaay too many plants on my first few attempts. You live and learn. Since then I have come to appreciate that less is, indeed, more!

A greenhouse full of plants grown NFT-style.

Daniel Wilson invites us to rethink what gardening in earth vs. gardening in water really means to the sustainability of indoor gardening.

Allow me to paint you a picture…

It’s a beautiful day in Anywhere, USA. It’s 10:30 a.m. and somebody just woke up, had their herbal tea and is now ready to tackle a long day of transplanting young plants into 7 gallon containers of Sri Lankan coco. They hop into their biodiesel powered 4×4 and head straight for the local grow store to pick up the pallet of coco it’s gonna take to fill those 120 containers. After dropping a cool $1,500 for the medium and another $250 for containers, they load up their rig and jump back on the 101 and it’s off to work. Sound like anybody you know?

There’s obviously a fair amount of energy someone’s just expended and they haven’t even started “work” yet. It’s pretty obvious this is a labor intensive method, but it’s well worth it because they’re growing organically, right? Oh … they’re using synthetic coco fertilizers, run drain-to-waste? But don’t they live in the woods? What happens to the run-off? Thank goodness nutrients come in 5 gallon containers because we’re going to be getting through a whole lotta nutes using the drain-to-waste method, right? Okay okay … I’ll quit this righteous talk. But let’s take a minute to ask ourselves a far more relevant question:

Q: Is it really sustainable to continue shipping millions of pounds of growth media all over the planet?

The current practice of bagging soils and shipping it indiscriminately around the globe has helped propel container soil/coco growing to its current popularity in the indoor grow scene. Though this is, without a doubt, a productive technique, it certainly makes the business of growing in earth a very petroleumintensive practice. Most of the organic growers I talk to take great pride in the natural grow medium they use and feel it’s the ecologically appropriate way to garden … as nature intended. Very few growers consider the great costs incurred by transporting that bag of earth conveniently to their local garden shop. The trucking of this relatively abundant resource (earth) has become quite commonplace in both greenhouse and year-round gardening circles. We rarely give a second thought to the amount of energy the bag of earth we depend upon so much represents. In fact, many growers are so confident in the sanity of these perpetual shipping practices that they will buy brand new bags of earth for their next cycle of plants to follow this round. Alas, very few would consider the idea of composting their used grow medium to be used to generate future harvests.

That being said, we need to consider what would happen if the shipping of soils for thousands of miles just becomes impossible … due to regulations on shipping or even a reluctance of a region to want to give up its precious carbon source, perhaps seeing it a better idea to keep it local and grow food in it as opposed to trading it for money. I know, I know, some of this might seem pretty far out and unlikely but it’s these awkward questions that lead us into discussions which begin to propagate solutions for the future. The critical thinking necessary to tackle issues before they become an “issue” is what we need to strive for as a garden and farm-based civilization. Past populations both benefitted and suffered from the methods they preached and practiced. It’s only in hindsight that clarity begins to develop and we are able to steer a course for the better.

So this leads me to our next Q & A.

Q: What is the most sustainable grow medium for the future of indoor and greenhouse cultivation?

For this question there is no simple answer.

1) The renewability of coir fiber is promising, but unless coir is a local product we are still faced with the shipping issues.

2) Naturally derived soils are another obvious option but, as with coir, unless we can solve the shipping dilemma it too falls short with regard to its practicality over time.

3) Stone wool (aka rock wool) products are a mainstay of commercial growers and are a fairly sustainable option – but it takes intense amounts of energy and large factories to process into forms well-suited for plant cultivation. And there’s still the matter of shipping, as far as from Holland to California at times: yikes.

4) Regional soils offer a pretty attractive option as we could build soils from an area’s most naturally occurring resources. This might mean West Coast Soils, East Coast Soils, Deep South Soils … you get the gist. This would make for minimal shipping, and it just makes sense.

5) Expanded clay pellets are another option with a light and dark side. Though made out of naturally occurring inputs, it (like stone wool) is energy intensive to make and costly to ship. More often than not it’s coming all the way from Germany!

6) Local water sources all over the planet offer a reusable and renewable way of growing healthy food, fiber and medicine. It’s possible to pump water vertically from indigenous terrestrial aquifers, or when available, benefit from naturally occurring snow melt driven by gravity.

Is it really possible that water could be considered a viable alternative to growing crops in a conventional substrate? What about plant nutrition? This leads us to our next question …

Q: Besides Aquaponics, don’t most high performance water culture applications rely on inorganic nutrients to work most productively?

Hydroponic applications use mineral salts to provide plants with the nutrition they require to grow and bloom. Most hyper-oxygenated water culture methods tend to greatly increase the efficiency of nutrient uptake in the plants’ root zone. This, in turn, maximizes these naturally occurring earth elements by offering them to plants in their most available forms. Typically you can run your nutrient solution at 40%-70% strength when compared to regular application recommendations for any given nutrient. Combine this with the closed loop nature of the majority of water culture applications and you are feeding your crops and also managing our planet’s most precious resource in a responsible, efficient manner.

Q: Isn’t that still using petroleum-intensive inputs to grow plants? So what’s the difference between this and using petroleum to ship soils?

Most notably, the difference is the reduced emissions from the avoidance of burning fossil fuels to ship transcontinental distances. Besides, this efficient nutrient uptake and constant recirculation gets the most out of both the nutrient and the water. Dissolved minerals in solution make the need for a conventional growth substrate relatively unnecessary in modern gardening applications. This can result in another way for gardeners to save.

Now let’s really get down to the bottom-line with this whole water angle:

Q: Sure seems like it takes a lot of plastic to make a hydroponics system … don’t they make that out of petroleum too?

This is without a doubt the least sustainable aspect to any plastic-intensive hydroponics application. Keep in mind, though, that the majority of soil cultivation is in plastic soil pots … which are often not reused. Most hydroponics systems incorporate as much recyclable content as possible in the form of HDPE (which currently has a LEED rating), PP (Poly Propylene) and other relatively benign plastics. At the present time there are no viable substitutes for PVC & ABS plastics. Hopefully in the not-so-distant future, plant-based polymers may offer a more sustainable substitute. When a hydroponics system is designed and built professionally it should be something that can be used for many, many years. It’s only over this period of time that the practicality of using the plastic finally balances out the negative impact of the plastic itself. With that said, avoid hydroponic plastics if you’ve no intention of reusing it over and over.

Some Conclusions

Whether you’re a fan of soil or water as your grow medium, one thing is for certain: producing consistently good results has to be the common denominator in any crop production strategy. There’s no shortage of different time tested techniques to get sound results. The ever-evolving challenge is how we can achieve the results we expect without disproportionately depleting our planet’s natural resources.

LEDs replacing HID grow lights within the next decade is pretty unlikely, but we can make responsible substitutions as these new technologies become available. Modern water culture methods are one of the most implementable techniques we can use to reduce our carbon footprint as growers. Though not perfect, water culture provides a genuinely organic grow medium at the turn of a wrist. Put down that bag and pick up the hose.

Some final food for thought:

Plant life as we know it conceivably evolved in the oceans long before our earth’s mantle was broken down into what we now consider soil. It was only when single-celled organisms came to the rocky shores of these primordial continents that terrestrial plants even began to exist.With that said, all plant life has its most ancient DNA, which is still able and very willing to adapt back to water. So if the seas were the Petri dish that plant life developed in, isn’t the ocean essentially just a constantly circulating, well-aerated solution of H2O and dissolved salts? Sound familiar?

Step 1: Rediscover Your Soil

You have a few options for turfing your turf:

1. Cut it off and compost it, then feed it back into your soil.

PRO: it exposes the soil right away, so you can get growing sooner.
CON: back-breaking work, only partly alleviated if you rent a sod cutter.

2. Mow your lawn very close to the soil, then mulch (suffocate) the grass with a light-proof material, such as layers of newspaper (10 sheets thick). It helps if you wet the newspaper before laying it down, to jumpstart the decomposition process and keep it from blowing around. Top the newspaper with 6-12 inches of compost, straw, leaves, grass clippings, manure and/or topsoil. Everything naturally decomposes into the soil.

PRO: much easier to do and the decomposed plant material feeds your soil, making it more fertile in the long run.
CON: takes awhile (allow at least two months) to breakdown the sod, depending on moisture, temperature, your worm population, and whether you’re planting seeds or transplants. It helps the mulch breakdown if you run the sprinkler on it once in awhile.

3. Chew it up and mix it into your soil with a rototiller or by hand.

PRO: it’s more efficient and takes up less space than removing and composting the grass, and your soil directly benefits from the nutrients as the grass decomposes.
CON: depending on your rototiller, climate and season, it’ll take at least three rototilling sessions over six to eight weeks to break down the sod.

4. Flip the blocks of sod upside-down.

PRO: for a small area, this is the most efficient and effective method.
CON: this method may confuse the soil microbiology — allow a month or so for everything to acclimatize.

Keep in mind that larger plants, such as shrubs and trees, have deeper roots then grass and so will likely need more topsoil than what is usually found beneath lawns. Even if you’re just planting a vegetable garden, the soil under your lawn has likely been compacted by foot traffic and will need additional soil, compost, and TLC to give it the fertility and conditions necessary to grow food. You can also use a garden fork to gently lift and aerate the soil.

“The lawns in the United States consume around 270 billion gallons of water a week—enough to water 81 million acres of organic vegetables, all summer long.”
- Heather Coburn Flores, Food Not Lawns

Step 2: Strategy, Design and Structure

Most vegetables (e.g. carrots, garlic, potatoes) grow best when you raise them above the ground level somewhat — and it’s easier for you to work with them that way, too. Some gardeners build wooden frames (e.g. 2ft by 6 ft by 1 ft high) and build up the soil inside so that the bed is a foot above the ground level. You can also rake soil from either side to create a row, then pat down the peak to flatten it. Squash, potatoes and cucumbers grow well in mini-hills, but this isn’t a very efficient use of space. Try to leave paths between your raised beds or rows, to make it easier to move around your garden.

For some interesting garden strategies and methods, Google:
- lasagna gardening
- square foot gardening
- SPIN gardening (small plot intensive)
- biointensive gardening
- no till / no dig gardening

Must-haves for the complete garden:
- rain barrel to collect water and avoid the cost/waste/limitations of municipal water sources
- compost area for leaves, kitchen scraps (not meat), plant clippings, and sod
- worm bin to produce super-powered worm castings to feed your garden

“The lawn is one of America’s leading ‘crops,’ amounting to at least twice the acreage planted in cotton. It is estimated that there are roughly 25 to 40 million acres of turf in the United States. Put all that grass together in your mind and you have an area, at a minimum, about the size of the state of Kentucky, though perhaps as large as Florida.”
- Ted Steinberg, American Green: The Obsessive Quest for the Perfect Lawn

Step 3: What’s for Dinner?

Low-maintenance crops:

salad greens: simply sprinkle the seeds, rake them into the soil, pat everything down, and water to trigger germination. Cut the leaves as needed to make salads, leaving the plant to continue growing. Different varieties of greens prefer different temperatures, so you can keep yourself in salad from early spring through fall by planting a few different kinds.

strawberries: buy bare-root transplants from your local nursery or ask a gardener friend for some “runners.” June-bearing strawberries will fruit prolifically in June/July the year after planting and thereafter, while ever-bearing strawberries produce over the summer months within the first year. Once planted, strawberries will produce for many years, sending out “runners” which will root and grow into new plants.

garlic: garlic cloves are planted in the fall, pointy-end up, about 6 inches apart, 2 inches deep, then covered with grass clippings and/or leaves and left to grow until harvest the following spring/summer. Very little water is required, even in hot, dry summers.

Popular crops:

sweet corn: firstly, be sure to purchase certified organic seed to avoid any contamination from genetically-modified corn. Corn is a high-maintenance crop, requiring fertile, nitrogen-rich soil and ample, frequent watering.

tomatoes: bush (determinate) varieties can grow in tomato cages or with short stakes; vine (indeterminate) varieties need a trellis or taller stakes and like to be pruned. Frequent watering and fertile soil are necessary. The UGM team highly recommends trying flavorful heritage varieties.

Kid-friendly crops:

pumpkins: these needy squash will benefit from frequent watering and excessive attention. Plant your seeds in a large hill of compost (with cow, chicken or horse manure, if you can find it), plant 6-10 seeds a few inches down, and water generously. Pumpkins need warmer temperatures, so plant only after all danger of frost has passed. Thin the seedlings down to 2 plants before they get too big.

sunflowers: choose a large variety, like Russian Mammoth or California Greystripe.

In Canada & the USA:

1. Click here to download the seed-starting spreadsheet (courtesy of Maggie Wang).
2. Enter the “Frost Free Date” for your region in the spreadsheet. (To find your last frost date for the US, click here; to find your date for Canada, click here.)
3. The spreadsheet will quickly calculate all sowing and planting dates and place them in the appropriate fields.
4. Print your chart and get ready to plant. Easy peasy!

In the UK:

1. Click here and select your region from the drop-down menu, then click “SET MY FROST DATES.”
2. Then click here (or select “Veg, Fruit & Herb Calendars” from the webpage’s left-side menu) and choose whether you want a calendar for vegetables, fruits or herbs.
3. Ta da! Print your calendar and pull on your Wellies.

Step 4: Ongoing TLC

Weed seeds can remain in soil for many years. Mulch is one of the best organic ways to prevent weeds, which will compete with your plants for space, sunlight and nutrients. Typical mulches include grass clippings, leaves, newspaper with soil or compost on top, cedar chips (expensive!), straw, hay (often full of weed seeds), and compost. Simply lay down 5 inches or so of material around your seedlings, covering as much of the soil surface as you can. This will suffocate weed seeds and stifle their growth, while providing a perfect environment for your worm helpers.

“Lawns use ten times as many chemicals per acre as industrial farmland. These pesticides, fertilizers, and herbicides run off into our groundwater and evaporate into our air, causing widespread pollution and global warming, and greatly increasing our risk of cancer, heart disease, and birth defects. In addition, the pollution emitted from a power mower in just one hour is equal to the amount from a car being driven 350 miles.”
- Heather Coburn Flores, Food Not Lawns

Conclusion

Be patient with your new garden. It takes at least a few years for a new garden to perform properly. Healthy soil is key to your garden’s success and the nutrient value in your food crops: love your soil, and it’ll reward you.

WORDS: Simon Hart

Give The Worms Some Credit

We all want to use items that increase our garden’s fertility in the hopes of explosive yields. With that as our aim, there is one item that stands out as a must-have for all soil and soil-less gardens: worm castings. Vermicomposting is the use of worms to break down organic material. Worm castings are the result of their digestion process. This process will give you some of the highest quality castings available and help you create a more technical and successful garden experience without a lot of effort.

Current research show extremely complex benefits from the use of worm castings in agriculture. A green technology, vermicomposting is the epitome of reduce, reuse, and recycle. Research continues and our knowledge of these unsuspecting creatures in the soil shows a fascinating connection between the worms and overall ecosystem health. Their effects on soil biology, nutrient availability, and the complexity of their decomposition of organic materials are just some of the things being studied. Although we are just starting to understand the relationship between earthworms and healthy soils, worms have been fascinating people for millennia.

Cleopatra, queen of the Nile, decreed that worms were sacred and were not to be harmed. The Greek philosopher Aristotle declared them to be the guts of the soil. The great biologist, Charles Darwin, who may be best known for his theory of evolution, started his scientific work looking at earthworms. In fact, he spent the latter part of his scientific career looking at nothing but earthworms at Down House, his country estate just outside of London. He was fascinated by them and utterly convinced that worms were among the unsung heroes within the natural world; in 1881 he published his life-long research on earthworms. In one project detailed in his work, he took small coal stones, spread them over a field, and left them for 20 years. He then dug a trench to see how far down the worms had moved the coal. Talk about long-term research.

WORM WISDOM
Worm castings are an amazing soil amendment, but go easy on them! They typically contain 5 times the normal levels of nitrogen found in regular soils, 7 times more phosphorus, and 11 times more potassium! Worm castings also contain calcium, magnesium and other micro-nutrients as well as tons of beneficial organisms and microbes that help to restore soil life and begin recreating the soil food web. Worm castings rule!!

The Knowledge

The industrious nature of worms is a power that can be unleashed on all unsuspecting gardens. While all urban gardeners are familiar with worm castings, most buy their castings at their local shop because it is very convenient. But given just a little space, time, and knowledge it is possible to grow your own castings. Not convinced that it’s worth the effort? Have a look at the benefits and then the actual work involved in growing worms and supplying your own rich, microbial super-charged soil amendment.

Research shows that vermicompost stimulates plant growth even when plants are already receiving optimal nutrition. Improved seed germination, accelerated growth and development, and increased productivity and yield are all scientifically validated claims. There are new theories, such as the possibility of transient plant growth regulators being absorbed by the humates which form in rich worm castings. Other benefits, such as disease prevention and the ability to repel pests, are possibilities, but there needs to be more study to understand the mechanisms behind these potential benefits.

When compared to regular compost, vermicompost stands out as the winner. Higher levels of plant-available nitrogen, phosphorus, potassium, sulphur and magnesium make vermicompost nutritionally superior. Microbiology is also more complex in vermicompost than standard compost. Why? First, vermicompost is processed at a moderate temperature range that never comes close to the140 degrees Fahrenheit (60 degrees Celsius) or higher achieved in thermophylic digested compost. This means that your worm castings will have more microbes meant to live at normal temperatures when compared to compost. Although the process is not entirely understood, it is also clear that worms release more microbes than they ingest, meaning that they are actually creating microbes during their constant eating.

Many composters will tell you that you need a thermophylic reaction (140 degrees Fahrenheit / 60 degrees Celsius or higher) or pathogens will not be destroyed. Research has shown that castings produced in pathogen-rich environments, such as human biosolids (I’m glad I don’t research sewage) contain no pathogens. Dissections show that something happens within the first quarter inch (5mm) of the worm that completely removes pathenogenic substances. That being said, I do not recommend that any gardener feed their worms biosolids.

There are estimates that there could be over 1,800 species of worms worldwide. Many of the worm casting available in retail shops are produced by African nightcrawlers. However, for the urban gardener looking to start vermicomposting, this is probably not the right choice of species due to its specific growing requirements.

Eisenia Fetida, more commonly known as a Red Wiggler, is indigenous to most parts of the world. This particular worm is extremely tough and adaptable, able to handle a temperature range from 32-95 degrees Fahrenheit (0-35 degrees Celcius), and the eggs or cocoons can survive short periods of complete freezing. This species is commonly used in commercial vermicomposting and is easily accessed by hobby gardeners through Internet sales. Before you order your worms, you had better have somewhere for them to live. There are many small home-sized worm farm units available. Some are more efficient and complicated than others. Remember that vermicomposting is a type of farming, not an industrial process, so bigger isn’t necessarily better. A savvy gardener will want to master the basics prior to a significant investment in equipment.

The Experience (in brief)

My first experience with vermicomposting began last year when, to the horror of my colleagues, I placed a worm bin in my office. My boss was quick to inform me that if it started to smell that would be the end of it. The pressure was on, so I put in my bedding and a half pound of worms and started the feeding frenzy.

I placed approximately 44 pounds (20 kg) of food waste in the bin over 14 weeks. I was amazed at how quickly the worms processed material and everyone in the office was stunned that there was essentially no smell other than a mild earthy aroma. This first batch of quality vermicompost got me hooked, and I would like to pass this concept along as a suggestion from one gardener to another.

I have moved on from my office bin, which in the end was too small. I am going to move my worm adventures outdoors into a very straightforward continuous flow wedge. Essentially I am going to build a three-sided open-end structure made from straw bales. To begin, I will add material and then worms against the back wall. After that I will continue to put in bedding and food sources. Once the pile reaches the open end I will take the straw bales from the closed end and move them to the open end. At this point I will harvest the oldest material to use as vermicompost and begin moving the pile in the opposite direction. This will get rid of the issue of removing the worms from my compost because they will move into the fresh material as you take away the digested castings. This was an issue with my office bin where I had to take the castings out and create small piles, then remove the top layer as the worms retreated to the base of the piles. Follow this with taking the base of each pile (which contains most of your worms) and put it back in the bin with fresh bedding and food. You can always buy new worms every time you renew your bin, but this adds cost to the exercise. That money can be better spent on other things by keeping your worm population healthy and productive.

Giving Your Worms a Home

To manage your worms properly you need to consider five essentials:

1. A hospitable living environment: the best worm farms have the best bedding. Things like straw, peat moss, coir, newsprint, cardboard and even dried leaves all make excellent bedding and can provide different benefits when blended together. You are looking to create a moist environment with lots of air pockets and a high carbon to nitrogen ratio. I have found a blend of straw and coir to be an excellent mix. A pH range of 5-9 is acceptable with a level of 7 being ideal.

WORM WISDOM
Adding grit to your bedding can help worms process more material. Inputs such as soil, powdered limestone, rock dust, egg shells and zeolite can provide this abrasive material that worms use in their gizzards. Note that all of these items will also provide extra benefit when added to your soil-less mix as well.

2. A good food source: worms are what they eat, so your food source is very important. Vegetable and fruit peelings are excellent, and coffee grounds are great when available. Kelp meal is a good choice, but remember that worms are sensitive to salt. Corrugated cardboard is also a good food source because of the high protein glue used to bind it. Commercially, there are many more food sources, including manures; but for the urban gardener it’s fine to stick to what you might put in a standard compost bin.

3. Adequate moisture: worms need a damp environment to get the job done and be happy while doing it. The moisture content in the bedding should be somewhere around 70-90 percent. This means you may have to add water at the start, but as you pile the kitchen scraps into the bedding the moisture should balance out to a good range.

4. Worms need to breathe, so make sure there is a good level of oxygen. If bedding becomes too compact it will force worms out by creating an anaerobic environment, which kills worms and will smell like something you don’t want in your garden.

5. Protection from extreme temperatures. The Red Wiggler is a perfect worm for vermicomposting because of its temperature range. However, you need to keep direct sun off your bin or pile because it can overheat the environment. Remember, also, that direct sun is toxic to worms. Outdoor vermicomposting does require some shelter planning, especially in Canadian winters that sometimes spill into the northern states too.

WORM WISDOM
Space is premium in small urban gardens, but many worm bins are small enough to fit under the kitchen sink or under your flood table. Most common small units use a top feed bed where you are adding food material into the worm bedding as it becomes available. Looking to upgrade? Consider a vertically stacked tray system for even more castings out of the same area.

The Reward

So now you want to use some of the black gold that has been growing in your worm bin. The finished product will range from 10-50 percent of the original weight of the material. But don’t worry because the best ratio to mix into your growing medium is about 10 percent. You can add up to 40 percent, but using over 40 percent seems to decrease its value, and castings can then actually slow the growth of plants. Use it as a top dressing or mix it directly into your medium. As a growing tip, if you are simply looking to enhance the microbial diversity in your rhizosphere, then consider the use of an aerobic compost tea to enhance the levels of various bacterial species. Remember that vermicompost has a much broader diversity of microbes than standard compost, and they reproduce rapidly at room temperature, so to use it in an aerated tea is an exceptional way to stretch its value in your garden. Without question, the addition of worm castings provides urban gardeners with accelerated plant growth. And to those urban gardeners up for the challenge, small-scale worm farming produces a growth accelerator while decreasing the waste that leaves your house for the landfill. I hope that you see some of the benefits now, and will experiment to bring vermicompost into your urban jungle.

Simon Hart is the senior technical advisor for Grotek Manufacturing in Canada. If you have any questions regarding vermicomposting or anything else garden-related, post them below!