Enlightened gardeners may be noticing something new in their potting media: a dark brown, fibrous material that has the look and feel of peat. The material is coir (pronounced “core”) dust. Like peat, it can be used as an organic component in potting media, or alone to amend garden soil or propagate plants.
So why would you choose one material over the other? One reason may have to do with your definition of a renewable resource. Peat comes from decomposed plant remains that have accumulated in waterlogged soils for thousands of years, and some people worry about diminishing peat bogs. Coir comes from a resource that many people consider more sustainable: coconuts.
The difference between peat and coir doesn’t end there. While peat tends to be acidic, coir leans toward a near-ideal pH, depending on the source. Some people also find that coir is easier to work with than peat. Coir retains more water than peat, making it a wise choice for many containers and hanging baskets. But the potential for high levels of soluble salts to accumulate is greater with coir-based than with peat-based soils. To eliminate any cause for concern, be sure to buy coir products from a reputable company.
Coir has been used for a decade in the United States by the commercial greenhouse industry and even longer by growers in the world’s tropical, palm-rich regions where it is produced, including Sri Lanka, Philippines, Mexico, and India.
Gardeners for years have lined their hanging baskets with long-fiber coir, and coir fibers are used to make common household items such as rope, doormats, and upholstery stuffing. Coir fibers are generated when the coconut husk is ground. Coir dust is the by-product of this process. Some of you probably have used chunks of coir dust to grow orchids, ferns, anthuriums, bromeliads, and other tropical plants.