Abstract: A process for producing hydrophilic growing media, preferably plugs, providing growing media having improved properties and a minimal amount of binding agent. The method forms a resilient, integral, dimensionally stable cohesive, homogeneous mass by contacting an aggregate with a hydrophilic urethane prepolymer and water. Upon curing, the prepolymer binds the aggregate material together. The mixing of the aggregate, prepolymer and water is conducted under specific, carefully controlled conditions, which enables the use of less prepolymer than would otherwise be necessary to obtain a given strength and stable air space. As result, trays can be filled without necessity of retooling.