pronounced: kroh-tuh-LAH-ree-uh re-TOO-suh
Crotalaria comes from the Greek κροταλον (krotalon), a rattle or castanets, referring to the sound the dried seed pods make when shaken; retusa is from the Latin retusus, dull, blunt.
This is a native of the warm areas of Africa, Asia, and Australia, but the exact native range is obscure: it is widely naturalized in the tropics.
The stems are erect, slightly ridged, and pubescent. The leaves are alternate, simple, oblanceolate, up to 9 cm long and 1 – 4 cm in width, with the lower surfaces shortly pubescent; there are 5 – 8 veins on each side of the midrib. The apex of the leaves is rounded, or occasionally acute, usually retuse, with the base cuneate. The petioles are anything up to 3 mm long, and there are tiny stipules, only half a millimetre in length.
The flowers are borne in a terminal raceme; they are typical pea flowers, yellow with fine purple lines near the base. The standard is about 1.5 cm long and 2 cm wide, the wings oblong-lanceolate, about 1.5 cm long by 1 cm wide; the keel petals short, the beak twisted, the margins ciliate.
The seed pods are inflated, green, maturing to dark brown or black, 3 – 4 cm long, with the 20-or-so tan to black seeds in each pod.
Crotalaria species are used as food plants by the larvae of some species of Lepidoptera, including those of:
• the Pea Blue Lampides boeticus;
• the Crotalaria Podborer Argina astraea; and
• the Crotalaria Moth Utetheisa lotrix.
Most parts of the plant are toxic to livestock. Although the plant is cultivated in some parts of the world, here it is found as a weed of roadsides and wastelands. In parts of New Guinea it is quite a serious weed. Being a legume, it does fix its own nitrogen from the atmosphere, and so can grow in very poor soils.
