ASTM International Standard Specification for Seed Starter Mix ASTM D5539-13

This specification covers the material characteristics, physical requirements, and sampling, of soil or soil-like material for seed starter mix. Starter mix may include natural soils and mixtures of natural or artificial materials for use in initial germination of seeds to the cotyledon stage. Seed starter mix shall be able to provide a germinating seed with basic needs such as aeration, water retention, surface crusting resistance, nutrients, soluble salts, optimum pH, sanitation, and bulk density that does not inhibit root elongation. Materials for seed starter mix may include vermiculite, sphagnum peat moss, perlite, coarse sand, expanded shale, clay, slate, peat humus, other peat products, composted organic materials, and other organic and inorganic materials.