Abstract
Summary.: Seeds of Agropyron repens (L.) Beauv, have little innate dormancy and germinate mainly during autumn, but germination may be delayed by cold, inadequate moisture or deep burial. Seedlings emerged from all viable seeds sown 5 cm deep but from only 4% of those 10 cm deep. Many seeds are viable when green and immature. At Rothamsted, spike emergence and flowering were earlier in 1970 than in 1968 and 1969 but more seeds became viable more rapidly in 1969. Higher temperatures in May and early June in 1970, and after flowering in 1969, probably account for most of these differences. Germination is facilitated by a diurnal alternation of temperature, but more old than young seeds can germinate at a constant temperature.