In the current study, gardenia (Gardenia jasminoides Ellis) plants were grown in three growth media; peat moss, clay and rice straw. Acidic wastewater from Manquebad Superphosphate Fertilizer Factory (Assiut, Upper-Egypt) was applied as soil drench (200 ml/pot) at 0, 10, 20 and 30 days. Pots of gardenia were arranged in a complete randomized block design with three replicates and repeated for two successive growing seasons. Peat moss produced the best vegetative and flowering growth of gardenia which could be assigned to its low pH and high organic matter content. Rice straw-grown plants had better vegetative growth than clay-grown ones in terms of plant height, number of leaves, branches and internodes, internode length, fresh and dry weights of shoots and roots, number and diameter of flowers and possessed the highest leaf contents of phosphorus, potassium, cupper and manganese. Plants grown in clay were thicker with bigger leaves resulting in higher total leaf area, and were characterized by the highest shoot-root ratio, more flowers and higher leaf contents of chlorophylls a&b, nitrogen and iron. The application of the acidic water improved vegetative and flowering growth and leaf nutrient content of those plants grown in both clay and rice straw. Increasing the frequency of acidic water application to 10-day interval caused a significant improvement in all vegetative and flowering characteristics and leaf nutrient content. In conclusion, using acidic water at 10-day interval can improve the quality of rice straw and clay to be used as good substitutes for peat moss.