Germination of Cool Season Annual Clovers1

Abstract

AbstractInformation on the effect of temperature on germination of the major cool season annual clover species adapted to the southeastern United States is limited. Such data would be useful in determining optimum planting dates and reveal differences between species. Seed of arrowleaf (Trifolium vesiculosum Savi.), crimson (Trifolium incarnatum L.), subterranean (Trifolium subterraneum L.), and Persian (Trifolium resupinatum L.) cultivars was placed on indented blotter pads in 90 ✕ 50 cm petri dishes. Petri dishes were placed in a low temperature incubator and subjected to day/night temperatures of 15/5, 20/10, 25/15, 30/20 and 35/25 C with 12‐hour light periods which simulate natural temperatures during clover establishment in the southern states bordering the Gulf of Mexico. Numbers of normal and abnormal seedlings were recorded every 2 days from the 3rd to the 13th day.Crimson and Persian clover had the fastest germination rate followed by subterranean and arrowleaf. Persian clover was the least responsive to temperature with only 11% difference in germination between treatments by day 13. Crimson clover reached maximum germination across all temperatures most rapidly with only 1 to 4% difference between day 9 and 13, but the number of abnormal seedlings was three to four times greater than the other clover species. Good germination of Persian and crimson clovers occurred at the highest temperature of 35/25 C. This could result in poor natural reseeding if hard seed content and dormancy decrease too quickly after seed maturation to prevent summer seed germination.Arrowleaf clover was affected most severely by the temperature treatments with maximum germination reaching only 17 and 9% under the 30/20 and 35/25 C treatments, respectively. Therefore, good arrowleaf seed germination occurs later in the fall than the other species which means less fall forage production and increases the risk of seedling damage by an early frost. Subterranean clover germination was depressed only at the 35/25 C treatment with the best germination rate at 30/20 C.