Optimizing Temperature Requirements for Clover Seed Germination

Core IdeasTemperature significantly affects the time and rate of clover (Trifolium spp.) germination.Germination and vigor were evaluated from -1.0 to 48.0 degrees C at approximately 1.0 degrees C increments.Tested cultivars maintained 80% + germination from 4.9 to 28.2 degrees C, on average.Temperature range for germination was much wider than reported in previous literature.Data will be useful in updating planting recommendations for producers in the US Southeast. There are many reports of failed clover (Trifolium spp.) establishments each year. Temperature is one of the primary factors affecting germination and significantly affects the time and rate of clover seed germination. The objectives were to determine (i) the temperature and time required to reach maximum germination and (ii) range in which germination will occur for six coated clover cultivars adapted to the US Southeast. Seed germination and vigor were evaluated in Petri-dishes incubated over thermal gradients ranging from -1.0 to 48.0 degrees C at approximately 1.0 degrees C increments where germination was counted every 24 h for 7 consecutive days. Base temperatures were calculated for each cultivar. Three parameter logistic growth models were used to find the minimum and maximum temperatures at which these cultivars could maintain 80% germination. Lorentzian distribution models were used to establish the temperature and time to maximum germination. These cultivars maintained at least 80% germination from 4.9 to 28.2 degrees C on average, although some germination was observed outside these extremes. The range at which these clovers could germinate was much wider than previously reported. Excluding 'Barduro', maximum germination occurred at 34.2 to 52.8 h after planting at optimum temperatures (10.9-17.2 degrees C). Barduro germinated so rapidly in the warmer temperature range that the full data set could not be used, as it did not conform to the same regression. Future trials will begin measuring germination at 12 h to better capture early trends in germination. These data will be useful in updating planting recommendations for producers in the US Southeast.