Sunn Hemp is actually a Crotalaria and not related to hemp. It is a tropical legume. This variety of sunn hemp is short-day sensitive, does not flower until late in the growing season, and, depending on weather and growing days, may or may not make viable seed. It has a tall, slender growth habit and can reach 10 feet in height. There is at least one other variety of sunn hemp, it flowers earlier in the season and does not get as tall, but we have not tested it. Unlike other legumes, the stalk or residue of sunn hemp is quite durable. Sunn hemp is heat- and drought-tolerant, adapted to a range of soil types, and seems to be relatively pest-free. White-tailed deer seem to prefer sunn hemp over many other legumes and forbs. Seeding rate was 19 pounds per acre.
These plots were drill planted in 7.5 inch rows in a no-till seedbed on a Heiden clay soil May 15, 2017, at the Noble Research Institute Headquarters Farm in Ardmore, Oklahoma. Planting depth was about 1.5 inches. Seed was placed on top of soil moisture, and 2.33 inches of rain fell over the next three days. No fertilizers, insecticides or herbicides were applied to this crop. Rainfall was below average after establishment.