Abstract: A plant growth medium is disclosed having a polyurethane matrix with at least 40% and preferably 50 to 55% open cells, and from about 36% to about 50% (and more for example 60%) by weight of a granular filler dispersed throughout the polyurethane matrix, which filler comprises about 69% to about 78% by weight of clay of relatively high cation-exchange capacity, such as a calcium-hydrogen montmorillonite clay, and from about 22% to about 31% by weight plant nutrients and their carriers.

Abstract: Methods of making and a self-contained hydrophilic plant growth matrix having excellent water holding properties for germination of seeds, propagation of cuttings and growth of plants are disclosed. The hydrophilic plant growth matrix is a dried, gelled plant growth particulate material mix, a cohesive plant mass which retains its shape and dimensional stability after rewetting. It may be formed in various shapes, such as pellets, plugs, cylinders, rods, blocks and the like. The gelled plant growth mix may be inserted in a plant matrix carrier or container which does not confine or impede root growth in any direction, such as an open cell foam, and preferably one which contains necessary nutrients for plant growth. The dried foam matrix has from about one-half of one to about five percent by weight, of a particulate, water-insoluble, water-swellable, cross-linked polymer dispersed throughout based on the dry weight of the plant growth particles.