Four plant species of woodland clearings - Avenella flexuosa, Chamaenerion angustifolium, Rumex acetosella, and Senecio sylvaticus - were grown on five different horizons of an iron-humus podzol profile. Reasonable growth was achieved only on the A0 horizon, which was rich in organic matter. The growth reduction on the other horizons was correlated with low concentrations of manganese and phosphorus in soils and plant organs. The restriction of so-called acidophilous species to acid soils is interpreted as meaning that they have a need for a high supply of manganese.