Sunn hemp is a tropical, nitrogen-fixing annual or short-lived herbaceous perennial. It is native to southern Asia, from Afghanistan through India to Indochina. Sunn hemp is a member of the bean family (Fabaceae). The species epithet, junceus , is Latin for “rush-like.” The erect, often sparsely branched stems resemble rushes ( Juncus spp.) and were used as a source of fiber for cordage, nets, etc. Sunn hemp is easy to grow in warm soils with a pH between 5 and 8. It is adaptable to any garden soil, but it does best in sandy soil. Because it fixes nitrogen, the plant thrives even in poor soils, as long as they are well drained. It is intolerant of standing water. Productivity, however, is greater in fertile soils. Seeds should be inoculated with Rhizobium before sowing to ensure optimum nitrogen fixation. Sunn hemp needs full sun. It suppresses other weeds with its dense canopy and strong root system. The plants are killed by frost, and the long stems of the residue should be chopped before incorporating it into the soil. Sunn hemp is a useful spring-sown, summer cover crop. It is also a forage crop for livestock, but because of the seed toxicity, animals should not be allowed to forage on the crop once it begins to flower. It is a suitable cover crop for a vegetable garden, fruit orchard or other permaculture garden. Sunn hemp is not a host of root-knot nematodes and is a useful crop where those pests are prevalent. Insects, Diseases, and Other Plant Problems: No major pests or pathogens. More information on Crotalaria .
Curated pairwise relationships between this plant and others in the library — who feeds
whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.
No curated interactions recorded for this species yet.
Also noted by NC State
Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell
apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.