Scarcity and the rising coats of peat initiated a search for substitutes. The solids of separated cattle manure and grape marc (wineries' waste pomace), which are common agricultural wastes, were composted and studied for their performance as potting media for Ficus benjamina cv. Starlight that served as model plant. The composts were used in 1:1(vol/vol) mixtures with peat moss or as a sole component of the potting medium and were compared with peat and peat + 20% vermiculite. Plant growth was enhanced and several important horticultural parameters, such as dry weight, stem diameter, height and leaf color, were improved in plants grown on compost-containing media. Physical and chemical properties of the media and nutrient elements composition of the plant material were determined. Because of these observations and analyses, we concluded that both composted separated cattle manure and composted grape marc were high-quality substitutes for peat.