Two populations of Agrostis stolonifera and seven populations of Festuca rubra from salt marsh and inland habitats were grown on a free draining soil and at two levels of soil waterlogging. The growth of A. stolonifera was stimulated by soil waterlogging while that of F. rubra was depressed. There was no difference between the two populations of A. stolonifera in growth response to waterlogging but the inland population had a greater Fe concentration in the shoots when grown on waterlogged soil than the salt marsh population. In F. rubra the yield of the salt marsh populations was generally less depressed by soil waterlogging than that of populations from free draining soils; the salt marsh populations also had lower concentrations of Fe and Mn in the shoot on the continuously waterlogged soil than the inland populations. It is concluded that the evolution of a degree of waterlogging tolerance has occurred in the salt marsh populations of F. rubra in response to the periodic flooding by sea water in their native habitats.