The fibrous outer covering of a coconut shell, called coir, has served for centuries as textile material for cultures lacking other cheap and abundant plant and animal materials for making thread, string and fabric. Today, people in developed countries encounter coir most often as doormats or linings for hanging flower baskets. Concerns about sustainable living have, however, stimulated an increasing number of coconut-based planting materials, among them soil-less planting medium, a peat moss substitute, and planting coils that control erosion. Learn the advantages coir brings to gardening.
The short pieces of outer coconut fiber used for planting media are leftovers from a comprehensive use of the coconut. Juice, fruit, husk and the long fibers of outer coating have already been processed. What remains is called coir dust, and other uses are few or nonexistent. One study noted that some piles of coir dust in Sri Lanka may be 100 years old.
Although the peat moss industry is quick to dispute cost, coir use for planting media seems to be more economical for several reasons. While coir dust must still be shipped to the US from great distance, high compaction of coir into bales and the durability of coir fibers, due to lignin and cellulose content, permit storage of more material in less space and for longer periods than for peat moss, important considerations for commercial plant producers.
Volume Needed for Planting Medium
Slightly less coir dust than peat moss may be needed to produce soil-less planting medium because of coir's water retention capacity. A volume of coir tends to "fluff" more abundantly than the same amount of peat moss. Results vary on assessing coir's overall water-holding and drainage capacities, but differences between coir, sedge (Florida peat moss), and sphagnum peat moss appear to be manageable.
Several tests of coir dust report higher alkalinity than peat moss, and one noted strong salinity. Information is apparently not yet available on standardized recommendations for fertilizing plants grown in coir dust. In one study, a higher potassium content of coir over peat moss appeared to offer some advantages to early plant development. Overall, neither peat moss nor coir dust manifested massive deviations from desirable neutral pH.
The advantages of coir dust stand out in sustainability. Peat moss is produced in Northern wetlands over long periods; replacing harvests requires a long wait for renewal. Attempts to duplicate peat production in Southern wetlands have thus far produced sedge peat moss, a markedly inferior product. The wide variety of environmental threats to all wetlands, combined with the growth of the residential gardening industry, raises serious questions about the sustainability of peat bogs needed to meet demands. So long as coconuts continue to grow, coir dust will gather and contribute to plant growth.
Trials at the University of Florida and the University of Alabama suggest that plant growth for tomatoes and peppers can be very similar using either a coir dust or peat moss soilless planting medium. Coir dust's superior water retention contributed to plant height, possibly an advantage or detriment to commercial growers.
Other Planting Uses
In addition to soilless planting medium, coir appears in mulching mats and planting coils. These log-shaped coils permit the planting of water-loving and ground-holding plants along stream beds and eroded slopes. By the time plants roots are established, coils have gradually begun to deteriorate.