Crotalaria juncea L.

Sunn Hemp

Herb

Annual

Vascular

Sunn Hemp is an introduced herbaceous annual in the Bean Family (Fabaceae). It is native to tropical Asia, but is widely cultivated in tropical and subtropical areas around the world. Sunn Hemp occurs throughout Alabama, but is most common in the southern half of the state. It occurs in fallow fields, in pastures, on roadsides, and in other disturbed areas. It is an annual with a tap root. Stems are 3-8 feet in height, sparingly branched above the middle with short, ascending branches. The stems are green in color and pubescent. Leaves are alternate, petiolate, simple, linear to oblong in outline, pubescent on both surfaces with silky, appressed hairs, and with entire margins. Flowers are produced in erect terminal and lateral racemes. Each raceme has 12-20 papilionaceous flowers. The flowers are bright yellow in color. The fruit is an inflated legume with 10-15 seed. Sunn Hemp contains toxic alkaloids, particularly in the seeds and pods. However, the variety ‘Tropic Sun’ is nontoxic and is grown as a forage for goats and cattle. Interestingly, the plant is also toxic to nematodes, and has been used as a cover crop in rotations to reduce the presence of nematodes. Sunn Hemp is allelopathic, releasing chemicals from its leaves that reduces the germination and growth of other plants. It is easily grown from seed, preferring a well-draining, sandy soil in full sun.—A. Diamond

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Not Native

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