A Quick Guide to Growing Plants in Coco Coir
Coir is commonly used in hydroponic media. Here’s a bit more about where it comes from and how to use it in your growroom.
Coco coir is a natural product made from the inner fiber of the thick husk that surrounds a coconut. It’s rot-resistant, durable, and lightweight. These characteristics perfectly serve the species, Cocos nucifera, because they help coconut trees find new habitats by allowing the giant seeds float across the sea to distant beaches.
Most imported coir comes from the southern coast of India and from nearby Sri Lanka, where it’s a byproduct of harvesting coconuts for food and fiber. Inexpensive and sold in compacted bricks, coir is used to make products like thick doormats, brushes, rope, upholstery-stuffing, and planting baskets. It is also increasing popular as a soil amendment.
Coir has some nice advantages as a soil amendment. (In soil mixes, use up to 40 per cent coir fiber.) It lasts longer, and it’s naturally free of bacteria, plant disease, fungal spores, weeds, seeds, and pathogens.
Coir has great water-holding capacity, too. It holds 30 per cent more water and is easier to rewet than peat moss. In addition, it creates airspace and allows better drainage in formerly compacted soils. In loose, sandy soils it holds nutrients to prevent them washing out.
Coir is also slightly alkaline, with a pH of 5.8–6.8. This reduces the need to usedolomite lime to neutralize acidic soil in the garden. The pH is ideal for release of its nutrients to roots. Coir is rich in potassium and micronutrients, including iron, manganese, zinc, and copper.
The high potassium content means that a gardener could use a fertilizer lower in potassium and still get good results. The other nutrients are a bonus; kind of like adding a vitamin pill to their diet. Because the pH of coir is more neutral than that of peat, some gardeners may find that coir does not work as well for acid-loving plants, such as azaleas and blueberries.
Coir can also be far more user-friendly than peat moss or rockwool. Rockwool, which was used for insulation before the creation of fiberglass batts or rigid foams, can lead to tiny particles getting into a grower’s eyes, mouth, nose, and lungs if proper protection isn’t worn.
It also requires a lot of energy to produce and take a long time to degrade when trashed. Peat moss is healthier, but mining peat disrupts wetland bog environments. As mentioned above, coir, on the other hand, is renewable.
Before use, compressed coir bricks must be soaked in a big container as they expand five to seven times in volume. A five-kilogram block, rock hard and impossible to cut, turns into 60 liters of fiber. A knee-high bucket per block works well, and a child’s inflatable wading pool is perfect for large bales. Soak the bricks for an hour, or overnight, then pull and tease it apart. Any coir you don’t use will retain its properties for many years, so just store it in a dry place.
Of course, coir is not perfect for all growing purposes. It tends to build up salt levels over time, so try to find coir labeled as “low-salt.” Also, if substituting coir for another amendment, be aware of the differences if produces. You might also need to increase nitrogen and decrease potassium when fertilizing. Still, don’t hesitate to try coir. It’s low cost, good for the environment, and can solve some grow media issues.
Written by Barbara H. Shaw
Barbara Shaw gardens, writes, and makes junk art in Oregon. She earned degrees in zoology, physiology, and journalism, and writes about science, health, growing things, and energy management. She also delights in reading, cooking, photography, eco-travel and has visited 60 countries. Married to a sports journalist, she embraces being a grandmother.