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Coco coir

Also known as Coir, Coco peat, Coir pith, Coconut fibre

Growing mediumDepends
Loose coir fibre from coconut husks Photo: Fotokannan · CC BY-SA 3.0

In short

Coco coir is the fibre and fine pith from the outer husk of coconuts, a by-product of coconut processing. It is widely used as a peat substitute because it holds water well and stays open and airy, but it needs washing and buffering to remove excess salts and it holds nutrients less well than some materials.

How it looks

Reddish-brown to brown material ranging from fine, dusty pith (coco peat) to longer fibres and chunky husk chips. It is usually sold as dry compressed bricks or blocks that expand greatly when soaked; one kilogram of dry coco peat swells to roughly 15 litres.

Signs

Unwashed or unbuffered coir can carry high sodium and potassium, which can show up as salt stress in sensitive plants. Because coir holds nutrients poorly compared with some media, plants in coir with no added feed can show nutrient shortage sooner.

What favours it

Coir comes from coconut-growing regions; India, Vietnam and Sri Lanka are the largest producers. Sourcing matters, because poorly processed coir can carry pathogenic fungi or weed seeds.

Prevention

  • Buy coir labelled as washed and buffered, or rinse it thoroughly before use to remove salts.
  • Hydrate compressed bricks completely before mixing, then drain.
  • Plan to feed plants in coir-based mixes, since coir holds nutrients less well than some other materials.
  • Mix with perlite, bark or other coarse material when a more open mix is needed.

Treatment

Start with the first step and move down only if the problem persists.

  1. If salt build-up is suspected, flush the pot with plenty of clean water and let it drain fully.
  2. Buffering, done by manufacturers, soaks coir in calcium and magnesium solutions that displace the bound sodium and potassium.

Pros and cons

Pros

  • Made from a coconut-industry by-product rather than dug from peat bogs.
  • Excellent water-holding ability, with a mix of fine and coarse fibres that keeps it light and porous.
  • Widely produced in South and Southeast Asia.

Cons

  • Can be high in sodium and potassium and must be washed and buffered before growing.
  • Holds nutrients less well than some other materials, so regular feeding is needed.
  • Quality varies; poorly processed coir may carry pathogenic fungi or weed seeds.
  • Coir and materials used to treat it can be allergens for some people.

Look-alikes

Peat moss
Peat is darker brown, dug from bogs, more acidic and harder to rewet once dry.
Pine bark fines
Bark fines are woody chips and dust, not fibrous husk strands.

Typical uses

General houseplant and container mixes, seed and cutting mixes, and hydroponic growing.

Sources

  1. Coir — Wikipedia
  2. What are the alternatives to using peat-based compost? — RHS
  3. Indoor Plants – Soil Mixes — Clemson Home & Garden Information Center
  4. Potting soil — Wikipedia

Written in our own words from these sources. Check a product label before using any treatment.