Crotalaria spectabilis Roth

Crotalaria spectabilis Roth




Crotalaria sericea Retzius, non Burm.f.

Vernacular Names


Showy rattlebox, showy crotalaria


Mahing men (northern

Geographical Distributions

Crotalaria spec­tabilis probably originated in tropical Asia, but is now distributed pantropically. It is also cultivated throughout the tropics, including Southeast Asia and in the south-eastern United States.


Crotalaria spec­tabilis is an erect, much-branched annual herb, and measures up to 2 m tall. The stem and branches are angular, grooved and nearly smooth.

The leaves are simple, and with persistent stipules. They are obliquely oblong-ovate, acuminate,  and measuring 3-10 mm x 2-8 mm. The petiole is 2-8 mm long. The blade is oblanceolate to obovate, and measuring (5-)8-14 cm x 3-8 cm. The upper surface is hairless while the lower surface appressed hairy.

The in­florescence is 15-50 cm long which is rather lax and with many-flowered raceme. The bracts are persistent, cordate, measuring 10-20 mm x 5-10 mm, and acute or acuminate. The pedicel is 8-13 mm long. The bracteoles are 1-2 mm long and lance-shaped. The hairless sepal is bell-shaped, measures 11-14 mm long, and with 5 unequal lobes which are longer than the tube. The petal is yellow.  The wings are obovate-oblong, and measuring 9-18 mm x 5-9 mm. The keel measuring 10-14 mm x 4-9 mm is rounded about the middle, with a short, incurved and twisted beak. The 10 sta­mens are united into one group by their filaments. The anthers are dimorphic, with 5 long, basifixed anthers on a short filament that alter­nate with 5 rounded dorsifixed anthers which are on a long filament. The ovary is narrowly oblong and hairless.

The fruit is a broadly clavate-oblong pod, measuring 4-5 cm x 1.5-2.5 cm, smooth, brown to dark brown when mature and with 20-24 seeds. The seed is unequal-sided heart-shaped, measuring about 3.5 mm x 4 mm, with the radicular side incurved and brown. 

Ecology / Cultivation

Crotalaria spec­tabilis is a plant of the tropics and subtropics, which requires an annual rainfall of 900-2800 mm and a mean annual temperature of 12-28°C. It is drought-tolerant. It occurs in open locations along forest margins and as a weed in cultivated fields, from sea level up to 1500 m alti­tude, in a wide range of soils, including heavy soils, with a pH range of 4.8-8.0.

Line Drawing / Photograph



  1. Plant Resources of South-East Asia No.11: Auxiliary plants.