PREMIER HORTICULTURE 713405 PRO-Mix HP Mycorrhizae High Porosity Growing Medium, 3.8 cu&#39;, Brown/A General purpose peat-based growing medium containing, a beneficial mycorrhizal inoculum These microscopic fungi attach to and colonize the root systems working in symbiosis with plants Contains: Canadian sphagnum peat Moss (75-85%/volume), perlite, Vermiculite, dolomitic and calcific limestone (pH adjuster), wetting agent and mycorrhizae