The use of composted grape marc (CGM) as a plant growth medium was investigated with Hypostases (Hypostases phyllostagya). Seven media were prepared using CGM mixed, in different ratios, with native peat and perlite. The following mixtures were used: 100% CGM, 75% CGM + 25% peat, 50% CGM + 50% perlite, 25% CGM + 75% peat, 50% CGM + 25%) peat + 25% perlite, 25%, CGM + 50%, peat + 25% perlite and 100% peat. The experiment was arranged in a randomized plot design with four replicates under greenhouse conditions. After a growing period of three months, some horticultural parameters were measured. Besides, some physical and chemical properties of the growing medium were determined. The mixtures of 50% CGM + 50% peat, 25% CGM + 75% peat and 100% peat were found to be most suitable based on the horticultural parameters. This was confirmed through the physical characteristics. Up to 50% composted grape marc can be used in mixtures with peat on account of its low cost and high nutrient content.