Reusable, sustainable, easy-to-use and a by-product of another industry? Could the ecological credentials of coco coir be any better?
Okay so, unless you happen live in India or Sri Lanka, chances are that the coco coir you use to grow your hydroponic plants has been shipped many thousands of miles in order to reach you, but as a hydroponic medium, coconut fiber not only boasts some great ecological qualities but it also has outstanding water and air holding capacity. It can hold eight to nine times its own weight in water without becoming anaerobic-even when saturated it can still hold on to around 22% air-beating even rockwool (around 10% air holding capacity.) Coco coir is therefore a forgiving hydroponic medium, allowing roots access to enough oxygen even when watered a little too enthusiastically with a warm nutrient solution. This makes it the ideal choice for beginners!
Coco coir also boasts antifungal and root promoting properties. Coco coir can suppress and protect plants from dreaded root diseases such as pythium and phytophthora.
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
- Completely environmentally friendly
What's in the bag?
There are three parts to a good, commercially available coco coir based growth medium: coco fiber, coco pith (coco peat), and chips. Each confers its own benefits to your plants.
Think of coco pith / coco peat as the sponge-like component of the mix. It looks like loose tea leaves and holds a large amount of water but, because it is smaller, it 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 therefore 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.
Fiber holds little water but increases the capacity of the growing medium 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 hold the least water. Think of them as a natural form of clay pebbles. They 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. 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.)
What Makes For Good Coco?
Coco coir is a natural product and, as such, the way it is harvested and prepared is key to achieving a quality end horticultural product. It 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.
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.
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. (Don't be tempted to use the 'ornamental variety' you sometimes find at your local garden center. This may still contain high levels of salt.) 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.
How To Test The Suitability of Coco Coir for Hydroponic Applications
You need to get an idea of the electrical conductivity and pH of your coco coir.
- Take a handful of coco coir and put it in a bowl. For the most representative sample, take a pinch from different parts of the bag.
- Mix with about 6 oz of di-mineralized (reverse-osmosis) water and leave for a few hours.
- Mix again and measure the pH.
- Strain off the coco coir so you are left with just the water. Measure the EC and pH of the water.
A good score is around 1.0 EC. (The lower the better.) 1.3 is acceptable.
The pH should read between 5.3 and 6.2.
Many growers treat coco coir like potting mix-i.e. they use it in regular plant pots. Some add a shallow layer of clay pebbles or clean silica rock on the bottom of the pot to aid drainage and to help air get pulled through into the root zone. Drippers are a great way to provide irrigation but many growers simply hand water too.
Do I Need Coco-Specific Nutrients?
Many manufacturers offer a 'coco specific' nutrient formula. This is because coco coir tends to hold onto phosphorus, while only holding a little calcium and releasing small amounts of potassium. Manufacturers counter this by providing extra calcium in their coco formulations, but not so much that it competes for potassium uptake resulting in a potential for potassium deficiency.
Do they work? Yes they do but you can also use a regular hydroponic nutrient too as they contain enough calcium. Some growers swear by their coco-specific nutrients though, claiming a purpose-made nutrient is best. Aim for a pH of around 6.0 as this will allow maximum availability of all nutrient elements. As with all hydroponic applications, a little pH swing is a good thing (say between 5.5 and 6.5) as it opens the doors to different nutrients.
All in all, coco coir is an amazing, exciting and easy to use renewable growing medium. It's easy to work with and is perhaps the best stepping stone for soil growers who want to take their first steps with hydroponics.