Seedling Growth of Crownvetch, Ladino Clover, and Alfalfa under Shade 1

Crownvetch ( Coronilla varia L.) is more difficult to establish than many other legumes. This difficulty has been attributed to slow seedling growth of crownvetch when shaded by competing vegetation. We wanted to determine 1) do seedlings of crownvetch grow more slowly under shade than seedlings of other legumes, and (2) do seedlings of weedy crownvetch, derived from plants which survived 2 years in a weedy nursery, grow faster under shade than seedlings of cultivated crownvetch, derived from plants grown in a cultivated nursery? We seeded ‘Penngift,’ ‘Emerald,’ “weedy,” and “cultivated” crownvetch, ‘Vernal’ alfalfa ( Medicago sativa L.), and common ‘Ladino’ clover ( Trifolium repens L.) in pots in the greenhouse during winter and again during spring. Seedlings were grown for 4, 6, 8, and 10 weeks under shade screens which transmitted 76%, 35%, or 14% of total solar radiation. Emerald, Weedy, and Cultivated crownvetch grew at the same rate, which indicated there had been no natural selection for seedling vigor or shade tolerance in the wedy nursery. Penngift grew more slowly than the other crownvetches. Crownvetch grew faster than Ladino clover in both winter and spring, and faster than alfalfa in winter. However, under higher radiation in the spring, crownvetch tops grew at the same rate as alfalfa tops, and crownvetch roots grew slower than alfalfa roots. We concluded that crownvetch grew about as well as other legumes under shade, and that low seedling vigor under shade is not a major cause of establishment difficulties of crownvetch.