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.

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

WORDS: Hydroguy

To all the consumers who find the sheer magnitude of the plethora of plant products bewildering: I feel your pain. To know nothing is sheer abysmal confusion, yet to know more does not seem to make product choice easier. When I see new growers walk into a store with a blank gaze I can actually observe their mental processes block as the overwhelming, yet exciting, stimuli flashes at them from numerous brightly colored bottles. This blank gaze often turns into a mix of confusion and skepticism. Too often novice growers think in terms of ‘Is it real or BS?’ whereas they should really be asking: ‘Do I need this?’ All products are of use in some or another application, it’s just a matter of finding what’s useful to you.

Base Hydroponic Nutrients

All organisms are elemental and require elements to live. We can look at our “vitamin/mineral” requirements as humans and it’s a short list. Plants have a similar “short list” and science has determined that, in order to technically survive, plants must get hold of them. Nitrogen, Phosphorus, Potassium (NPK), micro nutrients, etc. So these are the base survival needs. But to think of this as the limit of an organism’s needs is obtuse, just as a human would not have a great life eating cardboard for calories and taking vitamins. That said, whether your concern is simply production or quality of produce, you will need a base nutrient to supply the required minerals for growth. In the near-imperceptible chain of causality that affects plants outdoors, you have covered the most basic rudimentary needs. To qualify as a “base nutrient” all that is required are the N, P, and K in whatever ratio and micro-nutrients in sufficient quantity for your plant. Base nutrients are similar, but not the same. To arrive at a base nutrient (20-20-20 for example) a company can use various elemental compounds in combination; different combinations can have more or less purity at achieving the target mineral balance, and impurities are associated elements unintended for the outcome, such as arsenic. Aside from the ‘backpacked’ impurities in lesser quality products, different companies also use various arrangements of elemental compounds: for example, Calcium Nitrate or Ammonium Nitrate (among others) to provide the nitrogen. Different-sourced ingredients, as well as the final ratio of minerals, will all have slight variance in end use – those exact differences can be discussed another time.

Hydroponic base nutrients come in liquid 3-part, 2-part, and powder forms (”Why pay for water?”, some growers ask.) What you want is determined by preference, budget, availability, and trend. Read, ask your fellow growers, and inquire at your store to see what is buzzing – most base hydroponic nutrients are usable in any medium regardless of name. “Three part” can mean “use all three parts in conjunction” at different dilutions for each stage, or it can have one Grow and one Bloom for those respective stages and a third bottle added during both. “Two part” is often two parts for Grow and two for Bloom: four bottles mischievously pretending to be two. “Single part” is the actual two-part system with a Grow and a Bloom, or something representing those stages such as 20-20-20 and 15-30-15, and single part is also where you will find the “slurry” concoctions of mineral-based nutes with organics included. The ‘mineral/organic slurry’ is of some benefit to peat users since they add some cation exchange capacity (to be discussed later) to the inert peat without going all hippy.

“Well, I am using coco, so I need some coco food.” No, you don’t. Get better quality coco or add some cal/mag. Old coir was crappier because people didn’t realize the importance of desalinating it thoroughly, or some unscrupulous companies took the cheap route. Most coco-specific nutrients and only slightly increased in cal/mag and sometimes lessened in nitrogen – big whoop. If you are 100%-coco always then maybe it suits you, but I don’t see the importance.

There’s also the new “premium” base nutrients out there with labels donning expensive jewelry etc – these are still new to date for confidence, but if you’re willing to pay the piper for a trial there is some good buzz about some of them. As plant food becomes more of an organic chemistry art, we swerve less out of simple minerals and more into proprietary compounds we cannot know of even if we think we might understand them. That said, there still remains a need for disclosure and I can’t hold it against anyone for leaning to products with some transparency – in their attempt to avoid competitive replication, nutrient companies tend to alienate the consumer from understanding what their product is. Similarly, replication is a concern for consumers: nobody wants to add the same thing twice, and “just use it” is simply not convincing.

Organic Base Nutrients and Enhancers

The French Paradox. If you’ve never heard of it, pause to Google, but this is one example of a pretty basic point: there are more beneficial compounds in our food than simply vitamins. After the basic mineralogical requirements to sustain life, there are all the other bazillion compounds to improve the quality of life or, in our case, quality of produce of whatever form. An apple can technically minimally exist, or an apple can be packed with flavor, vitamins, and The Other Stuff (technical term – TOS). TOS represents turpines, flavonoids, organic acids, and a long list of stuff we don’t care to know of but still want to derive the benefits of. I don’t think it’s scientifically accepted that adding compost, kelp, guano, or another manure will increase the bio-active chemistry in produce, but “foliar feeding” isn’t accepted (in Canada) either – so my crutch is simple time-tested anecdotal observation: including organics will improve the quality of the end produce, thus increasing its flavor, aroma, and TOS.

Organic base nutes have come a long way in the last few years – mostly in convincing people they are worthwhile. We thought plants ate dirt, then realized they ate minerals from dirt (or water) – now it seems the geeks have decided that even larger organic compounds can make their way into the plants, such as vitamins. As always, it will always take science much longer to prove what people have been doing successfully for thousands of years, and continue to do today in “less advanced” areas of the world. The challenge for growers in the petrol world has been to match the yield of mineral nutes, and this has been displayed by various growers in enough circles to be generally accepted. It is a matter of substrate reuse and nurture, knowing what to add when – I will save details, but suffice to say if it is something you’re interested in it’s much easier today than ever, but still comes with a new learning curve.

Organics in hydroponics systems is something people would have balked at years ago; now there are products designed for such use. Growers have tested all forms of thick, organic sludge in their systems and, as much as commonsense still rules regarding buildup, slime clogs, and sugar coating, with a bit of elbow grease and absence of emitters or spaghetti hose many systems can run with nutrients not at all designed to be used in water gardens. The rigidity in this case is for generalization: you can’t tell everyone to do something that half will screw up. But, given the motivation and some knowledge, all these “can and can not” principles of growing can be realized as arbitrary guidelines. Beyond the liability of warranty and labeling, do what thou wilt.

ENHANCERS are there to enhance mineral nutes. You see, I think organics makes quality, whether it’s true or not. What is less debated is the notion that organic enhancers help make mineral nutes more available. Cation Exchange Capacity (CEC) are big words meaning “the ability for dirt to grab nutrients for later use.” Peat has nearly none, coco has some – either way, more is good. Humates, composts, organic sludge – these are midway rest stops for minerals between your bucket and your plant because they have a high CEC. Without a CEC component in peat, your nutes are pretty much only around as long as they are soluble – or, with reactive minerals, much less time. Without organic stuff, peat is only a fiber: it hasn’t any real ability to stretch the lifespan of a mineral nute until an organic component is added. Often a combination of things are used, such as guano or worm castings added to the peat – and/or some compost tea or other organic blend (or even a dash of base nute sludge, gotta love the sludge) with food irrigated in.

Next Up: Grow Store 102 – Bloom Boosters and Stimulants

What exactly is “bat guano” and why did it burn the $@#! out of my plants?

Because you used too much of it! Duh! High nitrogen bat guano is composed of the fresh bat poop on the bottom of the cave. After the guano miner dudes mine all the fresh stuff they start to mine the hard floor which is the high phosphorus bat guano. The high phosphorus guano is fossilized high nitrogen guano. Guano which is rich in nitrogen contains a considerable amount of ammonia and ammonium nitrate.  This is what gives the nitrogen component to the fertilizer. The nitrogen is released freely whereas the phosphorus and potassium are slower to release. This is what burned your plants. High nitrogen bat guano should be applied between 1-3 pounds per cubic yard. A tablespoon or two per five gallon pot. Take it easy!

Can you add too much compost tea?

There is good biology and bad biology. You only waste money by over-applying good biology. That is, unless you disturb the natural balance of the soil. In all our years of using compost tea we have never seen a negative effect – unless you drown your plants in it!

Can certain soils be “too rich” for some plants?

Yes, soil is a natural “buffer” for your plants but don’t think it will prevent you from totally frying your plants with too much fertilizer! Many people have proved this fact. Most problems arise through misapplication. Growers read teaspoon as tablespoon. Or guess that they put in 10 mills a liter instead of measuring it. Or they feed, feed, feed, feed, over and over again with no run off from the bottom of their pots. Or simply their pH is off. All these things are really common. Read the manufacturer’s instructions and don’t be afraid to call them up if you have question.

What’s best for fast growing veg? Pre-mixed products or a DIY mix?

Difficult question! In either case you should use a proper balanced soil. It needs good drainage, and rich with no more than 30% good quality compost: try to use 10-15 %.  For most growers (especially beginners) it’s better to buy a good quality soil than to try and make one up – but experienced growers sometimes enjoy the challenge or have a good recipe.

Do you have a tried and tested soil recipe?

The following recipes are great because they are so simple and very effective for growing heavy-feeding, sun-loving plants that enjoy lots of aeration around the roots.

Recipe 1
2 parts coco
2 parts peat
1 part earthworm castings
1 part perlite

Recipe 2
2 parts Sunshine no 4
½ part earthworm castings

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The glorious coconut has been providing us with much more than the odd Piña Colada for centuries. Traditionally, coconut coir (the outer fibrous husk) has been the backbone of “Welcome” doormats, brushes, sofa stuffing and horticulture for well over 100 years but, as far as hydroponics is concerned, coco coir started to make a name for itself during the late ’80s and early ’90s as a substitute for peat and rockwool, both non-renewable resources. In a nutshell (sorry, couldn’t resist), coconut coir is an environmental by-product of the long-established coconut industry. It’s a 100% renewable resource and the environmentally friendly alternative to bog dredged peat moss.

So what is it about coco coir that makes it such a popular replacement for peat and as a hydroponic medium in its own right? Firstly, check out its outstanding water and air holding capacity. Unbelievably, coco coir can hold eight to nine times its own weight in water! More importantly, coco coir holds a lot of air, in fact even when saturated it typically still holds around 22% air. In this respect it is superior even to rockwool, the world’s most popular hydroponics medium. Rockwool is a great medium but some beginners can easily run into trouble as it typically only holds around 10% air, leaving plant roots in danger of becoming oxygen deprived, particularly when the nutrient solution temperature is over 68-72°F (20-22°C). (The warmer a nutrient solution is, the less dissolved oxygen it can hold.) With coco coir, however, this type of overwatering (or, to put it more precisely, oxygen deficiency in the root zone) is avoided by the enormous amount of air that good quality coco coir can hold.

The amazing properties of coco coir don’t end with excellent water and porosity. Oh no! The best aspects of coco coir are far more varied! Did you know that coco coir possesses antifungal and root promoting properties? As coconuts spend long periods of time floating in the sea before they beach themselves and sprout a lovely new coconut tree, their physical dynamics have to be incredibly tough and unique to survive such a harsh, salty environment and still be able to sprout and grow when the time arises. These properties are available for you, the indoor gardening aficionado, to freely exploit in your quest for your perfect indoor garden. Recent studies have shown that coco coir has a great ability to suppress and protect plants from phythium and phytophthora, two very unpleasant root diseases that can quickly ruin your crop and put a real dampener on your day, week or month! This is very helpful if you are using organic-based nutrients, as these can contain high levels of urea that can build up and burn your plants.

Qualities of Coco Coir

• Coco has ideal pH in the range of 6-6.7
• It holds 8 to 9 times its weight in water
• It holds 22% air even when fully saturated!
• It has excellent drainage and air porosity for better plant growth
• The top layer always remains dry, leaving behind no chances of fungal growth
• It never shrinks, cracks or produces crust
• It aids in suppressing fungus gnats, to a degree
• Excellent cation exchange
• Its anti-fungal properties help plants to get rid of soil borne diseases (inhibits pathogens like phythium and phytophthora)
• Extremely easy to re-hydrate after being dehydrated
• It is a 100% renewable resource
• Lightweight
• Completely environmentally friendly

So what makes good quality coir?

There are three parts to a good coco medium: coco fiber, coco pith (coco peat), and chips. Each part brings its own attributes to the table.

Coco Pith

Coco pith / coco peat holds a large amount of water but is smaller and facilitates much less capacity to hold air. It is more lignin (woody) and decomposes very slowly. Properly aged, it contains the complex that holds potassium and sodium until it is fertilized and a stronger ion, usually calcium, bumps these off, thereby locking up the calcium and freeing large amounts of harmful salts. Proper aging of this coco pith is critical. It affects the crop time since a minimum amount of time is required to make this usable, at least four months, which reduces the amount of time available for use.

Coco Fiber

Fiber holds little water but increases the capacity to hold air; the more fiber you see in your coco mix, the more often you will need to water it. Fiber is largely cellulose and degrades fairly quickly. This degradation has an adverse affect on the stability of the medium. The length of these fibers is also critical to these functions as well.

Coco Chips

Coco chips combine the properties of the fiber and pith; they are approximately the same size as the fiber and positively influence air-holding properties while holding water. Chips hold less water than pith or fibers. They have the highest air to water ratio of all three parts. Achieving the correct ratio of these components is critical in developing a well-drained, well structured medium for growth, just as the proper preparation of the chemical characteristics is important by buffering the blend before use. (Hydroponic-grade coco coir growing medium has been treated so that unwanted potassium and sodium has been removed. This helps to ensure that the nutrients you later add to the coco coir can actually be used by your plants.)

Storage and Sterilization

Coco is usually stored in giant piles for a couple of years at its country of origin. Unless stored carefully, these huge coco piles can be susceptible to colonization by unwanted pathogens (partly due to the pH of the coco being favorable to pathogens) so, in this case, the coco must be steam or chemically sterilized in order to make it suitable for horticultural use. However, chemical sterilization can have adverse effects; and steaming destroys the structure of the coco peat while converting any nitrogen present into a toxic form, nitrite nitrogen; both destroy any beneficial organisms that are usually present. So what’s the solution? A coco coir supplier needs to control the coconut from harvest to bagging, remove the opportunities for unwanted seed and pathogen contamination, and carefully control the aging process directly. Only then will they stand a chance of producing the cleanest, most alive and most productive form of coco coir. Regulations vary between countries with regard to sterilization (Australia is very strict). Shipping microbes across continents is frowned upon by customs agencies. Some brands are inoculated with specific microbes that are either allowed to cross borders or are blended after landing on the shores where they ultimately will be used.

Finally, caring for the product through proper storage and packaging is critical, after preparation and again after packaging. Storing it too wet speeds decomposition. Drying in big mechanical driers can also have a detrimental effect on structure. In short, improper handling will drastically reduce the ability of the product to provide the correct root environment for proper root growth. Finally, consistency: a grower needs to be sure that they are growing in the same material crop after crop to ensure success. Imagine the heartache of losing a crop because the salts were not properly washed off your latest batch, or the coco peat is too decomposed – this REALLY happens!

So don’t be afraid to ask questions of your coco supplier. Look for an established supplier that sun dries the coco, one that incorporates the correct coco pith, coco fiber and coco chip fractions to get the best blend. This is specific to the grower’s irrigation system, the plants being grown, and the size of the pots used. For instance, you wouldn’t grow orchids in fine coco pith as they require lot of air! Conversely, any fast growing vegetable in warm conditions would enjoy lots of coco pith in the mix. Look for coco that is clean and washed correctly, one that is packaged and stored correctly, and one that is correctly aged.

Preparation

Let’s take a look at how this natural product should be prepared by the manufacturer. This is the biggest concern in selecting coco coir for hydroponics use. The outer fibers of the coconut are removed by soaking them in water. This soaking process involves either the use of fresh water or, more commonly, the use of tidal water which can be very high in salt. As coco coir has an excellent cation exchange ability it tends to hold onto things like salt which, when used in a hydroponic or indoor set up, can wreak havoc on your plants. Good quality, hydroponic grade coco coir will have not have a high salt content, but you should always flush it through with a low EC nutrient solution before use until no more tannins are coming out. Tannins can easily be seen as they stain or color the water brown. Some indoor gardeners check to see if the PPM of the water coming out of the coco is the same as the water they’re putting in – but a more reliable method is the 1:1.5 extraction method which better determines the actual pH and EC of the coco itself.

The 1:1.5 Extraction Method

A reliable method for measuring the nutrient levels in coco coir is using the 1: 1.5 extraction method. EC and pH of the root environment can be determined by using this method. The pH and EC of the drain water generally deviates from the actual root situation, as coco coir is able to retain and release elements.

1) Take a sample of coco. This can be done with a soil core sampler or a trowel. To get a representative sample the coco must be collected from as many places as possible.
2) Collect the sample in a bowl and determine whether it contains the right amount of moisture. The coco has the right amount of moisture if moisture disappears between your fingers when you squeeze it. Add de-mineralized water if necessary and mix the coco.
3) Take a ½ pint (250 ml) measuring jug and fill it with just over 4 fluid ounces (150 ml) of de-mineralized water. Add coco to the ½ pint (250 ml) mark.
3). Fully mix and allow the slurry to settle for at least two hours.
4) Mix again and measure the pH.
5) Filter this material out and measure the EC of the water remaining.

The target values for EC are between 1.1 and 1.3 (of course, lower is acceptable too!).
Target values for pH are between 5.3 and 6.2.

Reproduced with permission. Copyright CANNA.

The best way to irrigate coco coir in pots is via drippers. This is the best way to ensure that the growth media remains consistently moist (but not overly wet).

Coco-specific Nutrients

There are a number of manufacturers out there who offer a ‘coco specific’ nutrient formula. These specific formulations are based on the tendency of coco coir to hold onto phosphorus, while only holding a little calcium, while giving off small amounts of potassium. The best nutrient formulations for coco coir will therefore have some extra calcium, but not too much as it will compete for potassium uptake resulting in a potential for potassium deficiency. So are they any better? Well, generally speaking any good, complete hydroponic nutrient is more than suitable for coco coir as these invariably contain all the calcium needed to provide for excellent growth in coco coir. However, for best results, a purpose-made nutrient is best. When feeding nutrients to plants grown in coco coir, aim for a pH of around 6.0 as this will allow maximum availability of all nutrient elements. Remember, a slightly fluctuating pH is a good thing (say between 5.5 and 6.5) as it opens the doors to different nutrients. As for feeding times and frequency, that is really going to depend on what type of system you are running; but for those replacing their peat mix or rockwool with coir there is essentially nothing you need do differently, as far as feeding frequency, flushing, et cetera goes.

So there we have it. Coco coir is an amazing and renewable medium that is ‘top class’ for both performance and benefits. So go on and try this amazing medium, you’ll be glad you did.

CONTRIBUTORS:
Geary Coogler, B. Sci. Horticulture, HORTISOL North American Research
Adam Hanscom, General Hydroponics

A mother plant is there for one thing and one thing only. Cuttings. Lots and lots of lovely cuttings – or “baby chimps,” as I call them. If you grow plants that are sensitive to photoperiod you’ll want to let her bask under at least 18 hours of light per day so that she remains permanently in vegetative mode. She just grows and grows and never flowers, providing you with all the cuttings you need. Pretty amazing stuff when you stop to think about it. So you see, it doesn’t take a genius to figure out that a mother plant is the central pillar of any productive indoor gardening operation.

So why is it that so many of my fellow gardeners neglect their mothers? (Heheheh … I’ll let you fill in the gaps on that one!) Time and time again I find them in a right old sorry state, sprawled out and legging up in a dull corner of a vegetative room, looking old and decrepit with lots of brown, dead foliage at the bottom and untrained gnarly growth everywhere. (What a terrible image!) These offenders (and you know who you are!) think that all keeping a mother plant entails is to whack her in a 15 litre pot and fill it up with their chosen growing medium – oh and occasionally feeding it when she starts to wilt. It’s a crying shame. Too often the attitude is “keep the mother going” rather than “keep the mother thriving.” I don’t know about you, but it’s plainly obvious through good old common sense, let alone science, that the health of the mother plant has a direct bearing on the health and future yields of the scores of cuttings she produces!

Dedicate Some Space

Experienced growers have a dedicated mother room or tent. They don’t mind giving up this space and using the extra power because of the many benefits and conveniences that having a mother plant to hand brings. For one thing, growing from cuttings is way faster than growing from seeds every time. You can also flip a cutting over into flowering at any point, whereas you have to wait for a seedling to mature before it will do the business. Seeds also cost money, sometimes quite a lot of money, and they are often fairly unpredictable. On the other hand, you can be sure that all cuttings taken from the same mother will perform in the same way, so you know exactly what you’re going to get every time. That said, make sure you choose a good’n! You’re after a vigorous plant that yields well, resist pests and rot, and is pleasing to all the senses! Furthermore it’s a real bonus to have a mother plant that produces cuttings which are easy to root. Even plants of the same genus can vary incredibly – some taking twice or three times longer to root than others. So you definitely want to take rooting time / ease of rooting into consideration.

Choosing a system

Right then, we’ve established that you really, really need to take care of your mother plant. And no doubt some of you will have seen them thriving at friends’ houses in big pots and them being fed passively with drippers or a watering can. But if you really want her to thrive, the best choice is to treat her to her very own active hydroponics system. A Waterfarm, Aquafarm or similar single top feed bucket system is an excellent choice and it certainly won’t break the bank. Also, it’s a far more hands-off method. After you’ve filled the top bucket with well-washed clay pebbles, all you’ll need to do is keep the reservoir topped up and change the nutrient solution every week or two, and that’s about it. I have the drippers on constantly – especially when the mother is well established – as they can be very thirsty buggers. The growth is incredibly fast in these systems, meaning you can take lots of cuttings and your old dear will replenish herself in no time. Using a hydroponics system also gives you more control over the nutrients available to your mother plant. For instance, some growers like to decrease the levels of nitrogen available to the mother plant (by about 10%) prior to taking cuttings, claiming it promotes faster rooting.

Taming the Beast

As I mentioned earlier, it’s all too easy to allow your mother to become out of control. As you take more cuttings from your mother plant it will become bushier and bushier. Where you remove one growth tip to take a cutting, two will take the lead in its place. And two become four, and four become eight, etc. Eventually you end up with the mother plant equivalent of an afro. You can either do some serious remedial pruning, or start afresh by turning a cutting into a new mother plant. When taking cuttings, think like a hairdresser and try to shape your plant so that most of it is under a good amount of light. There’s no point in letting a mother plant get too tall and pointy – take these tips out and try to develop a candelabra-shaped plant instead.

Candelabra

The perfect shape to aim for when pruning your mother is a candelabra. This allows the most growth tips access to positions with optimum light levels.

Lighting

Remember, even if you’re not using all the vegetation she produces, your mother plant needs to thrive. It’s this intrinsic ‘health’ and ‘vigor’ that your cuttings will take with them when they become plants in their own right. Remember, your mother plant “sets the pace” so she needs to bask under lots of light. The dull corner of a veg room is far from ideal. If you have a separate vegging chamber, don’t be tempted just to stick her in there. For starters, your mother plant is likely to be a vastly different size to plants that are in early veg – she needs her own dedicated light. Many growers use 125 – 250 watt compact florescent units or some go the whole hog with a 250 – 400 watt metal halide HID. It’s unlikely that you’ll need anything more than this unless you’re growing up a monster – and if this is the case perhaps it’s worth considering growing more than one mother? CFLs need to be placed closer to the plant. For this reason, I personally find that a metal halide with a large, wide dispersing reflector is more practical.

Keep Things Fresh

After prolonged use a mother can become incredibly bushy, making it more difficult to take good sized cuttings. At this point it’s worth considering replacing your mother with a cutting from itself. This is a good time to give things a real deep clean – rinse out the hydroponics system that’s supporting the mother with a mild bleach solution. Remember that disease and pests on your mother will invariably be passed to any cuttings taken from her. So look after her! Depending on how well you take care of her, she will keep going and going for years before those characteristics you love her for start to wane. “How long?” you ask. Well, this is difficult to say. Some growers change their genetics every 6-9 months. I know of others who’ve been using the same chromosomes for as many years! But here’s a rule of thumb: as well as diminishing yields, a particularly telling sign is rooting time. If you are used to your mother producing cuttings that root in, say, ten days, and suddenly it’s taking two weeks or more, you may want to consider sourcing some fresh new genetics from seed and starting over.

18 or 24?

The jury is still split over whether mother plants prefer 18 hours of light a day or 24. Certainly it’s more natural to allow your plants to have some “dark time” – and your mother room lighting electricity costs will be reduced too. It’s less hassle to just plug a light in rather than faff with timers (and maybe electricians) so a lot of growers take the ‘lazy’ option of 24 hour light. Some Dutch growers I know even claim that it produces more vigorous plants!

Mothering Tips

• Dedicate a standard sized grow tent to your mother plant. Use a control unit, and a 5 or 6 inch extractor to maintain temperatures at 73 to 82°F (23 to 28°C) and relative humidity at around 60%.
• Don’t grow your mother plants in coco coir. After a few months it tends to lock out nitrogen – which is an essential primary nutrient for continued growth.
• Rotate your mother plant from time to time to ensure more even growth.
• Remove all dead leaves. Check right inside the mother plant as she gets bushier.
• If you insist on growing your mother in a pot, periodically check the roots to ensure the plant is not becoming too pot bound. If this is the case, use a sharp, sterile knife to remove around an inch of the root ball (messy business!) and re-pot in a larger container. It looks brutal, but your mother will thank you for it!
• If you are growing your plant in a hydroponics system (recommended) make sure you keep the reservoir topped up and check that the pH is always around 5.8. Completely refresh your nutrient solution every 7 – 10 days.
• Use a grow light rich in the blue spectrum like a metal halide HID or a CFL. The 250 watt Enviroglow is a great choice. It screws directly into the reflector – no need for a ballast or electrician if using with a timer. Remember to ask for the blue version for growth!
• If using CFLs, remember they do not give off much heat. They work best a lot closer to your plants than a standard HID light.

Everest’s Mother Plant Shopping List

Ok, so you’ve decided to grow up your very own mother plant? Here’s a list of things I think you’re going to need:

• A standard-sized grow tent. The Homebox is a great choice. Also, the Homebox Light (not designed to be lightproof ) is a good budget option as a mother plant does not require set amounts of complete darkness. Size assembled: 39 1/2 by 39 1/2 by 78 3/4 inches (100 by 100 by 200 centimeters).
• 1 x Top Feed Bucket System, e.g. Nurticulture Flo Gro FG500, or GHE’s Waterfarm / Aquafarm. All these systems use a ring dripper that ensures a wide dispersal of nutrients to all parts of the root zone.
• 1 x 400 watt HID lighting system with a Metal Halide lamp and a large reflector for a wide spread of light. The Sunpulse range also features a dedicated vegetative light (6.5K).
• A pair of Ezi-hangers to hang and adjust your lights.
• S hooks – to attach your Ezi-hangers to the top of your grow tent.
• Clay pebbles.
• Extraction kit: 6” carbon filter + fan + ducting

Inflow: Passive should be fine through the grow tent venting. If your mother plant becomes very large, you could supplement this with an RVK100 style fan. Blow fresh air in at the bottom of the tent.

• Control unit (automate inflow and extractor fan speeds to regulate temperature and humidity).
• High quality vegetative nutrient pack. Ask your local hydro store for advice on the water quality in your area and make sure you buy an appropriate nutrient.
• Hygrozyme is a personal favorite of mine for keeping mother plants (as well as vegetating cuttings) in tip top health. It helps to break down any old root mass and stimulate fresh new growth.
• Trichoderma or funganic powder – beneficial bacteria for a healthy root zone.
• I’m assuming you already have your humidity, pH and conductivity (nutrient strength) meters! If not – make the investment!
• Cheap and affordable “auto-top up” systems are available if you are planning to go away for an extended period.
• Don’t forget scalpels, rooting hormone, propagation media (e.g. rockwool cubes) and propagators for taking all those lovely, healthy cuttings!

So good luck everybody and remember: look after your mother and she will look after you!