Three growing media consisting ofSphagnumpeat mixed with either a siliceous sand, a sandy soil or a fen peat, were studied in relation to the effect of indolebutyric acid (IBA), applied at 2.0 g I‐1as a 10 s root dip, on the growth of containerized ‘Carrizo’ citrange seedlings. Plants grown in the fen peat mixture showed the highest root development and vegetative growth, but were insensitive to IBA. This auxin improved the growth of plants grown in both sand‐and soil‐based mixes. Similar trends were observed for nitrogen (N) and phosphorus (P) foliar concentrations, but potassium (K) concentrations in leaves were only increased in plants grown in the soil‐based growing medium.