Polyurethane foams containing equal amounts of commercial unmodified cornstarch and a polyisocyanate-terminated polyether exhibit properties suitable for horticultural applications. The use of cornstarch in the foam formulation increased the volume by one-fourth as compared to the foam without cornstarch. This volume increase represents an economic advantage of 20% savings based on material cost. When cornstarch or corn flour is added to the foam formulation, the foams are more resistant to compressive force. Upon wetting and draining, the foams prepared with no auxiliary blowing agent and containing corn products exhibit higher volumes than do the unfilled foams. Radish seeds planted inside 25 mm cubes of foams began to sprout after 1 day. Early developmental growth for the plants was similar in the control and cornstarch-filled foams. Spectroscopic analyses of the starch-containing foams revealed that 60-70% of the cornstarch was metabolized within 4-5 weeks by a microbial consortium. Control polyurethane foams were not affected by the microorganisms tested.