Tips For Best Use Of Coir

Tips For Best Use Of Coir

Impatiens comparison between Densu coir, Metro mix and Pro mix

A lot of research has been done in the last 20 years on the use of coir or the fibers that are harvested from coconut husks. There are several companies that supply and manufacture growing substrates with coir. As with any substrate or substrate component, growers should conduct their own trials to evaluate the effectiveness in their operation.

Several trials have been conducted at the University of Florida’s Fort Lauderdale Research and Education Center on the use of Densu coir to grow both foliage plants and bedding plants. In each trial, plants were grown in 100 percent Densu coir and compared to growth in a standard blended sphagnum peat-based substrate with approximately 60 to 80 percent sphagnum peat with perlite and vermiculite. All comparisons were unbiased experiments and the results presented do not constitute an endorsement of Densu coir or the sphagnum peat blends.

Coir was one of two substrates used to grow dieffenbachia plants. Average shoot dry weight of plants grown in coir was 27.4 grams while the average shoot dry weight in peat substrate was 27.3 grams. Similarly, average calathea shoot dry weight in coir was 29.3 grams while in the peat substrate the average shoot dry weight was 26.3 grams.

Impatiens were grown in coir, Metro mix and Pro mix. Plants grown in coir were equal to or larger than plants grown in both Metro mix and Pro mix. The coir used in this study had similar initial pH, soluble salt, CEC, total porosity, air-filled porosity and water holding capacity to Pro mix (Table 1). It is important to note that growers should check initial pH, soluble salt, water-holding capacity and air-filled porosity before using coir, because products from different manufactures may vary. Furthermore, trials should be conducted prior to converting production areas over to coir-based substrates.

Advantages of coir (based on results from experiments conducted with Densu coir) include:

• It’s easy to work with
• Plant growth in 100 percent coir was comparable to other substrates evaluated as long as fertilization was included; it works well with controlled-release fertilizer products applied as top-dress or incorporated into the substrate
• Wets easily and quickly; also re-wets easily if plants dry out between watering
• High moisture content
• Less dust when dry (ease of mixing and handling when dry)

Disadvantages include:

• Crop growth might vary; crops that grow well in peat-based substrates appear to grow equally as well in coir.
• We do not recommend growing plants in 100 percent coir but using it as part of blend that replaces sphagnum peat; suggested blend to try might have 60 percent coir with vermiculite and perlite.
• You have to add nutrients to the media to get good crop growth; coir without fertilization produces poor plant growth.

Table 1. Substrate chemical and physical properties.

pH Soluble salts (mmhos/cm) CEC (MEQ/100g)
Densu coir 5.5 to 6.2 0.37 2.2
Pro mix 5.0 to 6.6 0.26 3.9
Metro mix 5.9 to 6.5 0.86 6.1
Substrate Total   porosity % Air-Filled Porosity % Water-Holding Capacity %
Densu coir 93.26 26.00 67.26
Pro mix 92.00 23.00 69.00
Metro mix 66.00 19.00 47.00

The work summarized above does not imply an endorsement of any product mentioned. All studies were unbiased trials. The data is a fair representation of how the plants tested grew in various substrates. Results may vary with other plants as well as under different growing environments. From the data we have collected, coir appears to be a good substrate for growing a variety of plants.

About the author: Kimberly Moore is an associate professor of Environmental Horticulture at the University of Florida’s Fort Lauderdale Research and Education Center. She can be reached at

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