Four temperate grasses (Festuca arundinaceae, Festuca X Loliumhybrid,Lolium boucheanumandLolium multiflorum) were grown under irrigation at the Dohne Agricultural Centre. The object was to determine the monthly growth and nutritional value of the grasses. The effects of environmental features on the growth rate of the pastures were investigated. Polynomial regression of the environmental features against growth rate was used to create transformed values, which were then subjected to stepwise linear regression. In some cases it was possible to describe the growth rate, expressed as the increase in yield (g ha−1) per minute of day length, in terms of temperatures, minimum humidity and increasing day-length. The growth rate ofF. arundinaceaaereached a maximum at a mean average temperature of 18°C, and that ofL. boucheanumat 16°C.Festuca arundinaceae'sgrowth rate is depressed less by higher temperatures than that ofL. boucheanum.Seasonal growth patterns (t DM ha−1month−1) and fibre and N content are reported.