pronounced: kroh-tuh-LAH-ree-up PAL-lid-uh
Crotalaria is from the Greek κροταλον (krotalon) , a rattle or castanets, referring to the sound the dried seed pods make when shaken; pallidus is Latin for pale, or pallid.
This is a common weed of roadsides, paths and waste places on Magnetic Island, and its flowering spikes are quite pretty before the seed pods begin to form. It is probably a native of tropical Africa, but it is so widely spread throughout all the tropical regions of the world that its origins are obscured. It is used as a ground cover and as a green manure crop in many parts of the humid tropics, less so now that it is realized the plant is host to a number of agricultural pests. In tea, rubber and coconut plantations in Sri Lanka and south-east Asia, and in cocoa plantations in West Africa, it is planted between the rows to reduce erosion. In the south-eastern parts of the USA it was grown extensively for soil sanitation (it is a nitrogen-forming legume), as a forage crop and for green manure until the 1960s. Its use for these purposes has declined, because if the seeds get accidentally mixed into fodder grains it can cause poisoning. In west Java, a fermented drink was formerly made from the seeds. Seeds were boiled for two hours, wrapped in banana leaves and left to ferment for several days to remove poisonous components. In Cambodia the flowers are used as a vegetable. In Indo-China a kind of coffee is prepared from roasted seed. In Vietnam, the roots are sometimes chewed with betel-nut.
In traditional medicine, the plant is used to treat urinary problems. A poultice made from the roots is applied to painful swelling of joints, and an extract of the leaves is taken as a vermifuge. In Laos it is used to reduce fever.
The plant is an erect annual or short-lived perennial, which under favourable conditions is said to grow up to 2 m high, but here barely seems to reach 1 m. The leaves are trifoliate, the leaflets obovate or obovate-elliptic, usually 2.5–7.5 cm long and 1–4 cm wide, the upper surface more or less glabrous, the lower surface with sparse hairs. The petioles are 2.5–5 cm long, stipules generally absent.
The flowers are bisexual, with 5 petals, in dense, usually erect, spike-likeinflorescences, pale lemon-yellow. The rachis is 14–40 cm long. The pods are pendant, up to 5 cm long, and brown at maturity. The plants are reproduced by the kidney-shaped seeds, of which there are about 36 per pod. The plants flower and fruit throughout the year.
The various Crotalaria species are food plants for several caterpillars, including those of:
• the Pea Blue Lampides boeticus;
• the Crotalaria Podborer Argina astraea; and
• the Crotalaria Moth Utetheisa lotrix.