Crotalaria spectabilis Roth
Family
Leguminosae
Synonyms
Crotalaria sericea Retzius, non Burm.f.
Vernacular Names
|
English |
Showy rattlebox, showy crotalaria |
|
Thailand |
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.
Description
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
References
- Plant Resources of South-East Asia No.11: Auxiliary plants.
