Differences between eight related grasses within the Lolium-Festuca complex in conditions of severe water shortage were investigated. Transparent covers were used to restrict the access of rain to field plots of pure stands of Westerwolds ryegrass (Lolium multiflorum var. Westerwoldicum), Italian ryegrass (L. multiflorum), hybrid ryegrass (L. multiflorum x L. perenne), perennial ryegrass (L. perenne), meadow fescue (Festuca pratensis), Italian ryegrass x meadow fescue, perennial ryegrass x meadow fescue, tall fescue (Festuca arundinacea) and three mixtures (Italian ryegrass with perennial ryegrass; Italian ryegrass with tall fescue; perennial ryegrass with tall fescue) grown in west Wales. Westerwolds ryegrass and Italian ryegrass died out after 12-15 months of exclusion of rain; meadow fescue, meadow fescue x ryegrass hybrids and perennial ryegrass died out after approximate to 2 years of exclusion of rain; tall fescue was still alive after 4 years of exclusion of rain. During the 2 years after the year of sowing, the loss of water from the top 1 m of soil was greater with tall fescue than with the other grasses. Tall fescue and perennial ryegrass had a low rate of leaf expansion, a small increase in length of exposed leaf sheath and a high weight per unit area of emerging leaf blade. Tall fescue had a greater number and weight of roots than the other grasses, particularly in the 50-100 cm layer of soil, on an adjoining, uncovered site. The order of suitability of the eight grasses for conditions of severe water shortage appears to be tall fescue > perennial ryegrass > perennial ryegrass x meadow fescue, meadow fescue, Italian ryegrass x meadow fescue, hybrid ryegrass > Italian ryegrass > Westerwolds ryegrass.
