Coco coir

Coco coir is a fibrous growing medium produced from the mesocarp (husk) of the coconut palm (Cocos nucifera), sold as compressed bricks, loose pith, chips, or blends with perlite. Though chemically inert and typically managed under hydroponic fertigation regimes, coir exhibits soil-like physical and chemical properties: high water-holding capacity (≈8–9× its dry weight), substantial air-filled porosity when properly hydrated, and a cation exchange capacity of roughly 30–60 cmol(+)·kg⁻¹ that preferentially binds K⁺ and Na⁺, displacing Ca²⁺ and Mg²⁺ — hence the universal recommendation for Cal-Mag supplementation and pre-use buffering with calcium nitrate (Caplan et al. 2017a, HortScience 52(9):1307–1312; Caplan et al. 2017b, HortScience 52(12):1796–1803). Caplan et al. established optimal liquid-organic-fertilizer N supply of ~389 mg·L⁻¹ in veg and ~283 mg·L⁻¹ in flower on coir. Etymology: Malayalam kayar, "cord." Synonyms/slang: coco, coir. → See also: Soil, Hydroponic, Indoor.