Winter growth of contrasting ryegrass varieties at two altitudes in mid-Wales.
7 cv. of perennial ryegrass, which originated from countries having contrasting winter climates and with a range of heading dates, were grown in simulated swards at an upland and a lowland site in mid-Wales between Oct. 1975 and May 1976. Measurements of growth were made at 1-month intervals. Mean soil temp. was c. 2 deg C cooler at the upland site than at the lowland site. Leaf extension and appearance rates were related to temp. but were faster (for a given temp.) in spring than in autumn. Many tillers died in the lowland (but not the upland) between Dec. and Feb., when the weather was dull and initially very mild. There was no evidence of frost damage to leaves. The differences in growth pattern between cv. were related more to date of heading rather than to geographical origin. The late cv. carried more and longer green leaves in winter and had faster leaf extension rates than early cv., although the differences were generally smaller at the upland site; by May, at the lowland site, the early cv. had the greater leaf extension rates. There was no indication of dormancy in any cv. The findings are discussed in relation to the measurement of winterhardiness.