Coir – a brief guide

4 October 2016
  • Whastsapp

The quality coir we use at ICL originates from the tropical island of Sri Lanka and from India.  This sustainable product is made from the pith of the coconut husk.   Here our growing media expert, Dr Jim Smith, outlines its strengths and limitations and what it can bring to the growing media mix.

Separated from the fibre, coir is screened, purified to remove sodium chloride, dried in the sun, compressed into blocks, palletized, and transported to our modern growing media facility in the UK.   Here it is mechanically reconstituted into a dry loose material and can be manufactured into growing media either on its own, or by blending with other bulky raw materials such as peat, bark and or wood fibre.

Coir has many benefits and, like all growing media ingredients, there are a few challenges that it is important to be aware of. 

Benefits and considerations                                                                                              

  • Light in weight when dry
  • Absorbs water readily, even when very dry
  • Medium cation exchange capacity, which will buffer some nutrients
  • Flows into pots and cells readily
  • pH around 6.0
  • Uniform particle size
  • Low air filled capacity
  • Brown in colour similar to soil.

 As with all growing media constituents, coir has characteristics that need to be considered or managed carefully to ensure the best results.   

  • During the manufacturing process, coir requires washing and some buffering at source to remove sodium chloride
  • Uniform particle size means AFP cannot be adjusted
  • Coir can appear dry on surface, but may still hold a lot of water underneath.


Adding coir to peat

As a peat diluent, coir can help reduce the peat content of growing media.  A light material, it can lower the bulk density of the growing media helping to reduce transport and labour costs.  It has also been shown to improve the acceptance of water in younger peats and dry peats and to enhance rooting.

When adding coir to a peat growing media mix it is important to consider the higher potassium levels – this may necessitate adjusting the fertilizer to compensate. Depending on the rate, adding coir may also increase conductivity.

The advantages of adding 10-15% coir to peat based growing media far exceed the disadvantages and make the end product far more uniform when handling water.

As with all the substrates in our Levington Advance peat reduced and peat free mixes, ICL only source quality products.   As a company we have to be satisfied suppliers operate ethically and sustainably and endeavor to source our quality coir supplies from companies with proven social accountability and quality standards.