Tropical Forages

Crotalaria juncea

Scientific name

Crotalaria juncea L.


GRIN: None listed

ILDIS: Crotalaria benghalensis Lam.; Crotalaria fenestrata Sims; Crotalaria ferestrata Sims; Crotalaria porrecta Wall.; Crotalaria sericea Willd.; Crotalaria tenuifolia Roxb.; Crotalaria viminea Wall.


Family: Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Crotalarieae.

Morphological description

An erect annual, up to 3.5 m tall. Laxly branched, depending on plant density (there may be a single stem in dense stands). Vigorous lateral roots and long taproot that can exploit deeply stored soil moisture. Stem ridged and pubescent, up to 2 cm in diameter. Leaves are simple; oblong-elliptical, 4‒13 × 0.5‒3 cm; sparsely appressed-pubescent above, more densely so below; petiole 2–3(-5) mm long; stipules 2–3 mm long, caducous. Inflorescence a terminal open raceme, up to 25 cm long, with 18‒20 bright yellow flowers, showy; sepals 5, hairy; standard erect, suborbicular, ca. 2.5 cm in diameter. Pod cylindrical, 3‒6 × 1‒2 cm, tomentose, light brown, containing ca. 6 seeds. Seeds heart- to kidney-shaped, with narrow end strongly incurved, up to 6 mm long, dark brown to black; loose when mature and rattling in the pod. About 33,000 seeds/kg.

Common names

Asia: kâk'tung (Cambodia); 菽麻 shu ma (China); san, sunn (India); orok-orok lembut (Indonesia); po:th'üang, thwax chu:b (Laos); putok-putukan (Tagalog), karay-kagay (Bikol) (Philippines); po-thuang (Thailand); suc sat, lue lac (Vietnam)

English: sunn hemp, sunn crotalaria, sann-hemp brown hemp, Indian hemp, Madras hemp

Europe: chanvre du Bengale, chanvre indien, crotolaire jonciforme (French); Sanhanf (German); sunnhampa (Swedish)

Latin America: cânhamo-da-Índia, crotalária (Brazil); cáñamo san, matraca, sonajuelas (Spanish)



Asia: Bangladesh; Bhutan; India


Throughout the subtropics and tropics


Leaves stripped to feed to livestock (e.g. as supplement to low-quality feedstuff).


Soil improvement when used as green manure (including to suppress nematodes).


Mainly used as a source of fibre (extracted from the bark).

Soil requirements

Adapted to poor soils but responds to fertilization; pH 5‒7.5; intolerant of salt and prolonged water-logging. On light, well-drained soils production is higher than on clay soils.


Drought tolerant, adapted to hot, semi-arid and arid areas.


Being a short-lived warm-season plant, suitable for a wide range of climates as long as there is a hot summer; can tolerate light frosts.


No shade tolerance reported.

Reproductive development

Sunn hemp is a short-day plant; long day-lengths favour vegetative growth, although daylength neutral selections exist. Fast growing; under favourable conditions reaching a plant height of 1.2 m in 60 days, 1.8 m in 90 days.


For green manure or forage, should be used at vegetative growth stage or at the beginning of flowering. Optimum cutting height to enable high yields and subsequent cuts should be about 30 cm.


No information available.


Guidelines for establishment and management of sown forages.


High seed germination; 40‒50 kg seed/ha when used for green manure or forage; 100‒240 kg/ha when intended use is fibre production; 1‒2 cm sowing depth. Nodulates readily with native cowpea type rhizobia. 150‒165 kg/ha nitrogen contribution have been measured in 60 days.


Responsive to P, K and Ca.

Compatibility (with other species)

Smothers weeds because of fast initial growth.

Companion species

Except for intercropping (with e.g. rice, wheat, Cenchrus americanus), C. juncea is generally not grown with other species.

Pests and diseases

Many pests and diseases are reported with varying degree of economic damage. To avoid build-up of disease and insect pressure, rotations are recommended.

Ability to spread

Although the pods are dehiscent, there is no indication of C. juncea being dispersed, to a major extent, by seed.

Weed potential

No information available.

Feeding value
Nutritive value

18‒22% CP content in hay has been reported. 0.29% P; 1.40% Ca; 60% digestibility.


Animals are reported not to eat C. juncea when it is green; forage should be dried. Restriction recommendations in terms of hay to be offered to cattle vary between 10 and 45% of the animals' diet.


As other species of the genus Crotalaria, it contains poisonous glucosides (pyrrolizidine alkaloids).

Feedipedia link

Production potential
Dry matter

Establishment yields 2 t DM/ha after 6‒8 weeks; thereafter, 3 further cuts at 4-week intervals may be possible.

Animal production

No data available.


2n = 16.  Self-incompatible; extensive cross-pollination.

Seed production

Up to 1.8 t/ha have been reported.

Herbicide effects

Fluchloralin and pendimethalin have shown to be effective for controlling early weed growth.

  • Forage potential restricted by concentrations of toxic glucosides.
Selected references

Chee, Y.K. and Chen, C.P. (1992) Crotalaria juncea L. In: Mannetje, L.’t and Jones, R.M. (eds) Plant Resources of South-East Asia No. 4. Forages. Pudoc Scientific Publishers, Wageningen, the Netherlands. p. 98–100.

Rotar, P.P. and Joy, R.J. (1983) 'Tropic Sun' sun hemp; Crotalaria juncea L. Research Extension Series 36. University of Hawaii, Honolulu, USA.

Sarkar, S.K., Hazra, S.K., Sen, H.S., Karmakar, P.G. and Tripathi, M.K. 2015. Sunnhemp in India. Central Research Institute for Jute and Allied Fibres (ICAR), Barrackpore, West Bengal, India.

Wang, Q., Li, Y., Klassen, W. and Hanlon, E.A. Jr. (2018) Sunn Hemp ‒ A Promising Cover Crop in Florida. UF-IFAS Extension SL-306. University of Florida, Gainesville, FL, USA.


A wide range of cultivars and elite lines are available, particularly in India with most being developed for their fibre quality and production. But some varieties have been developed for forage or green manure use (see Sarkar et al., 2015).

‘K-14’ (Cawnpore 14) Developed at Kanpur, Utar Pradesh, India for use as a green manure.

‘T6’ Released in India (~1974). Day-neutral variety which flowers at about 30 days after sowing ‒ suitable for green manure and fibre.

‘Tropic Sun’ Released in Hawaii, USA (2002). Selected for green manure and forage, not toxic to animals and is resistant to Meloidogyne spp. (root-knot nematodes).

Promising accessions

None reported.