Plant cultivation substrates for the soilless cultivation of plants, on which grasses and other useful and decorative plants grow virtually as on natural fertile soil, are produced in the following steps: (1) mixing flakes of at least partly open-pored foam plastics with nutrients, (2) mixing a synthetic resin adhesive with a 1-3% strength solution of a water-soluble alkyl and/or hydroxyalkyl ether of cellulose in the ratio of 1 part by weight of cellulose ether to 3 to 10 parts of adhesive, (3) mixing the mixtures (1) and (2), (4) drying the mixture (3) in a mould. Fillers can be added to the mixtures (1) and (2). The fillers used are in particular dry algae as an additive to mixture (2). Substrates with even better properties are obtained thereby.
