Experiments on the growth of Schoenus nigricans have shown that the plant grows almost equally well in base-rich and base-poor bog waters, at high and low Ca levels and between pH 4 and 8. The low levels of electrolytes found in raised and blanket bogs reduced growth slightly but not sufficiently to exclude the species. S. nigricans was shown to be extremely sensitive to Al ions, with a concentration of 0.55 mg/l causing a 50% reduction in root growth. Such Al levels in blanket bog waters are more frequent in inland than coastal areas. Al ions in ombrotrophic bogs are derived mainly from dust, and are absent or in very low concentrations in the blanket bogs of the west coast, because of the prevailing south-westerly winds from over the ocean.