Crotalaria juncea

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. 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.

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