Growing on Coco Coir

One of the most popular cannabis grow mediums is coco coir, sometimes referred to simply as coco. Coco coir (pronounced coy-er) is widely used in both grow rooms and outdoor gardens, in hydroponic and soil grows, and is as versatile as it is popular. 

Often used as a stand-alone soil replacement for hydroponic systems, coco coir can also be used as a soil amendment or combined with other mediums, such as perlite or vermiculite, to create a highly-absorbent, loosely-packed medium that enables significant nutrient uptake and rapid root development. If you aren’t already using coco in your grow, you could miss out on some of the many benefits that come with it.

What is Coco Coir?

Coco coir is made of the ground-up fibres of coconut husks. Once considered a byproduct and discarded, it was discovered in the last century that these husks, once ground, created a soil-like substrate that retained moisture well. Since then, coco has gained worldwide traction in the fields of organic farming, hydroponics, and especially cannabis growing.

Coco coir is suitable for many different grow systems. Its soil-like consistency and ability to retain water makes it an excellent medium for beginning growers, but it remains a favourite amongst more advanced horticulturalists as well. This is because, unlike soil, coco coir will retain water and moisture but is light and airy enough to allow oxygen to reach the roots, akin to hydro growing. For this reason, coco coir is widely considered a hydroponic medium, though it is frequently combined into soil mixtures to increase drainage, add moisture retention, and loosen compacted soil.

How is Coco Coir Made?

Coconut husks go through heavy and time-consuming processing to create coconut coir. The husks are soaked in a process called retting, which helps to dissolve cellular tissue and pectin, allowing for the easy separation of the coco fibre from the husk. Once soaking is completed, the husks are dried, sometimes for as long as an entire year.

The separated fibre is then further processed into the form in which it will be sold, either ground to a fine particulate, left in long, stringy fibres, or chopped into larger chunks, referred to as “chips.” Each of these forms of coir possesses its own unique attributes, which can be beneficial for different types or stages of plant growth.

Using Coco Coir in Your Cannabis Garden

Many first-time cannabis growers jump right into using coco coir when they begin gardening, and for good reason–its soil-like consistency and appearance can be far less intimidating than expanded clay pebbles, a Deep Water Culture or an ebb-and-flow system. Not all coco is created the same, though, and understanding the differences between the various types can help save you time and money later on in your grow and possibly sparing your cannabis plants from damage.

Coco Peat: Sometimes referred to as coco “pith,” coco peat is the ground-up husks of coconuts that resembles peat moss or soil. Because of its high water-retention properties, coco peat is not recommended to be used alone, as it will drown your plant’s roots and create ideal conditions for root rot. Combined with perlite for increased aeration, coco pith makes a fantastic non-nutritive substrate perfect for cannabis roots.

Coco Fibre: Coco fibre appears as the stringy, brown material recognizable from the outside of a coconut. These fibres are not nearly as absorbent as ground peat, making them perfect for adding aerating oxygen pockets to your coir mix while also reducing nutrient salt build up in your plant’s root system.

Coco Chips: Coco chips are just what they sound like: larger chunks of coconut husk that have been less processed than fibre or peat. These larger chips work well for creating air pockets within your growing medium but can also be used alone as a replacement for expanded clay pebbles. Their large size makes them acceptable for use in net pots, where the size of the medium becomes an issue.

Coco coir is most commonly sold in compressed, dehydrated bricks. These dehydrated bricks, unfortunately, tend not to possess the quality of their pre-mixed counterparts. Often, companies will use high-quality coco coir in pre-packaged mixes, similar to the high-quality soil mixes available from nurseries and grow shops.

Coco is also commonly compressed into pellets, similar to the popular peat moss pellets, or small pots, which can be used to start seedlings for easy transplant. In whichever form you choose to buy coco coir, its many benefits will quickly become evident.

Benefits of Growing Cannabis on Coco Coir

Growing on coco coir produces many benefits:

Excellent water retention: Coco coir can hold up to ten times its own weight in water, ensuring your roots will not dry up unexpectedly.

Great aeration: Coco allows significant airflow to the root zone, enabling more rapid and hearty root growth, translating into bigger, stronger plants with increased yields.

Simple introduction to hydroponic gardening: Because coco coir looks and feels so much like potting soil, many gardeners are inclined to try it out rather than jump into a more advanced hydroponics system. Many beginners choose to start out with a coco/perlite blend, which provides excellent water retention and optimum runoff simultaneously. However, because it is inert, fertilization is required by the gardener, just as in hydroponic growing.

pH neutral: Coco coir has a naturally-occurring pH level between 5.2-6.8, making it nearly neutral. This, combined with mixing nutrient solution, provides a gardener nearly complete control over their plant’s conditions.

Insect and pathogen-resistant: Coco coir is far less susceptible to insects, pests and pathogens than soil and potting mixes, significantly reducing the likelihood of an infestation or contamination. However, low-quality compressed bricks have been known to contain dormant insect larvae, so be sure to choose high-quality coir when making your purchase.

Environmentally sustainable: Coco coir is an eco-friendly product. It has become increasingly clear in recent years just how destructive the harvesting of sphagnum peat moss is on the environment. Coco coir, comparatively, is a renewable resource, reusing what was once considered waste, and creates jobs for those who farm and process the coconuts.

Reusable: One of coco coir’s greatest attributes is the fact that it can be flushed and reused. Unlike peat moss, coco’s hearty make-up will not break down after one or two grows. Nutrient salts can be flushed away, and the coco returned to its original neutral pH to be used again.

Of course, coco coir is not a miracle (though it’s not far off!) and does come with its own set of drawbacks as well.

Drawbacks of Growing on Coco Coir

Though coco enthusiasts have little negative to say about growing on coir, there are still some drawbacks worth mentioning:

Requires nutrient supplementation: Unlike soil, coco coir is inert, meaning the medium itself does not contain any nutritive elements for the plant. Thus, growers must provide all necessary nutrition in the form of a nutrient solution, as well as buffering the coco in preparation for use. Coco-specific nutrients are available for this reason and help balance Calcium, Magnesium and Iron, three nutrients that can fluctuate greatly when growing in coco. Many growers, though, find that a standard NPK (Nitrogen/Phosphorous/Potassium) nutrient line combined with a Cal-Mag supplement works sufficiently to provide plants with all the additives they need.

Possible salt content: The process of retting (soaking coconut husks to remove the fibre) is sometimes conducted in ocean water, which can introduce large amounts of salt into the coco coir and damage your plants. If it is unclear from the packaging how the coco was prepared, it is recommended to flush well before beginning work with it.

Cost: High-quality coco mixes can be very pricy, with the alternative being dehydrated, compressed bricks. While these bricks may be more affordable, they are usually of a lower quality than pre-mixed bags and may include high salt content, chemicals that were used to treat the coconut trees, or dormant insect larvae.

Whether you are an introductory-level grower or a seasoned veteran, the appeal of coco coir is undeniable. Useful in soil or soilless mixes or as a stand-alone hydroponic medium, coco coir is one of the most versatile gardening substrates available.