Crotalaria medicaginea  Lam.1786

pronounced:kroh-tuh-LAH-ree-uh meh-dik-uh-GIN-ee-uh

(Fabaceae —  the pea family)

subfamily:  Faboideae – the bean subfamily

common name: Trefoil Rattlepod

Crotalaria crotalaria medicagineatrefoil rattlepod crotalaria medicaginealeaf & flower comes from the Greek κροταλον (krotalon), a rattle or castanets, referring to the fact that the seeds become loose in the pod as they mature, and rattle when the pod is shaken; medicaginea is, I think, botanical Latin for ‘like medick’.

This native species of rattlepod is not as common on the island as either the yellow rattlepod or the Gambia Pea, at least in those areas of the island where I normally walk. There is a colony by the roadside in Horseshoe Bay, near where the road from Arcadia levels out at the bottom of the hill, and I have seen the occasional plant in Picnic Bay.

crotalaria medicagineathe pods crotalaria medicagineapod detail The trefoil rattlepod is usually found in sand or gravel, on hillsides, creek banks and in gullies. It is an ascending or decumbent herb or subshrub, 30 – 60 cm high, the stems usually more or less appressed pubescent.

The leaves are trifoliate, with the leaflets each having a notch at the apex. Each leaflet is 0.5 – 3.5 cm long and up to 1 cm wide, the upper surface glabrous and minutely stippled, the lower surface hoary or pubescent; the  petiole 4 – 15 mm long, the stipules about 1.5 mm long. The growth habit is rather variable, and there are some varieties as well. In some instances the leaflets have slight apical points.

The racemes are up to 17 cm long, 4 – 25 flowered, the pedicels up to 6 mm long. The calyx is about 4 mm long, and pubescent. The corolla is 4 – 12 mm long, yellow, often streaked with red; the wings 4 – 8 mm long; the keel with a beak, 3.5 – 10 mm long, twisted tightly at the apex.

The pods are less than 1 cm long, more or less pubescent, usually containing only 1 or 2 seeds. These seeds are about 2 mm long.

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.

The toxic alkaloids produced by some members of the genus are known to be incorporated by Utetheisa larvae and used as a defence against predators. Most Crotalaria species contain these poisonous alkaloids, which can cause damage to the liver, lungs and kidneys of grazing animals.

Photographs taken in Picnic & Horseshoe Bays, 2009, 2011, 2017

Page last updated 17th March 2018







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