The use of an adequate medium is very much emphasised in growing transplants. Due to their favourable characteristics, peats have long been used in production. With the depletion of peat resources the research of peat substitutes has come in the foreground. In the experiments cucumber transplants were grown using baked, expanded clay granules. Results have indicated that by mixing them to peat in a 50 % rate they could be suitable mineral material as a component for soil mixtures.