Plants are grown in expanded peat moss units which have been produced by intermixing an aqueous bituminous emulsion with peat moss in critical proportions of peat moss to bitumen, drying the mixture, and compressing portions thereof uni-directionally to form rigid bodies. The compressed bodies have a thickness which is a small fraction of their original thickness. These bodies are expanded by contact with water to form soft cakes, which retain their shape without the need for external constraint, while permitting normal plant and root growth therein. The expanded shape-retaining cakes have a thickness intermediate their original and compressed thicknesses.
