Germination of annual pasture species was studied under controlled-environment conditions in southwestern Australia at temperatures in the range from 4 degreesC to 35 degreesC. Subterranean clover (Trifolium subterraneum) and Wimmera ryegrass (Lolium rigidum) had a germination of 90% between 12 degreesC and 29 degreesC, whereas capeweed (Arctotheca calendula) had a high germination percentage in a much narrower temperature range with an optimum of 25 degreesC. Growth of subterranean clover, capeweed and Wimmera ryegrass between 28 and 49 days after sowing (DAS) was also studied at two photon flux densities, 13 and 30 mol m(-2) d(-1), and at diel temperatures in the range from 15/10 degreesC to 33/28 degreesC. Pasture species grown at a density of 1000 plants m(-2) accumulated at least twice the amount of shoot dry matter when subjected to temperatures of 21/16 degreesC and 27/22 degreesC, compared with a lower temperature of 15/10 degreesC and a higher temperature of 33.28 degreesC. Except at the highest temperature and at high photon flux density, capeweed had lower green area indices (GAI) than the other two species at 28 DAS. Crop growth rates between 28 and 49 DAS were higher in Wimmera ryegrass than in the other two species, whereas subterranean clover had a lower relative growth rate than the other two species at all temperatures and both photon flux densities. Subterranean clover and capeweed intercepted a greater proportion of the incident radiation compared with Wimmera ryegrass. The values of radiation interception and GAI were used to estimate the number of DAS to reach 75% radiation interception [f((0-75))]. The number of days to reach f((0.75)) decreased with increasing temperature from 15/10 degreesC to reach a minimum at 27/22 degreesC. The time taken to achieve f((0.75)) was always shorter by about 10 d when the photon flux density was 30 mol m(-2) d(-1) in the autumn compared with 13 mol m(-2) d(-1) in the winter. These results are discussed in relation to the early growth of annual pasture in the field.