Tests were made of the response ofPinus sylvestrisL. andPicea abies(L.) Karst, seedlings of different origin to a range of concentrations of soluble inorganic aluminium during a 12‐week period of cultivation in quartz sand under field conditions. Al and nutrients were supplied via the irrigation water (pH 3.6–3.7). The Al concentrations were 0, 0.37, 0.74, 1.85, 2.78 and 3.70 mM. The growth of Scots pine seedlings was inhibited when the aluminium concentration of the irrigation water was 2.78 mM or higher. The corresponding aluminium concentration for the Norway spruce seedlings was 1.85 mM or more. The results are discussed with reference to the soluble aluminium concentrations normally encountered in boreal forest soils.