Coir offers pros, cons

Coconut fiber, or coir, is becoming popular as a growing medium, but it’s important to understand its limitations and advantages before making the switch, said Julie P. Newman, farm adviser at the University of California Cooperative Extension.

Some advantages include high water-holding capacity, better air penetration and acceptable pH levels.

Coir readily absorbs water, so a wetting agent is not needed. Because of its high lignin content, coir breaks down slowly which keeps the medium structure open. This allows air to better penetrate, encouraging larger, healthier roots, she said. Coir typically lasts two to four years.

The pH of most commercially available coir ranges from 5.8 to 6.5, so liming is not required. There are no disposal problems associated with coir. It’s a waste product of the coconut industry. Coir also may deter fungus gnats and algae by keeping the surface dry.

The most common problem with coir is it can have an extremely high salt content, especially in lower grades. Coir high in salts should be leached before use.

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Coir has a lower cation-exchange capacity and it is high in phosphorous and potassium. Growers switching from sphagnum peat to coir need to change their fertilizer practices.

For more: Julie P. Newman, (805) 645-1459; jpnewman@ucdavis.edu.