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Crotalaria mitchellii Benth. 1848
pronounced: kroh-tuh-LAH-ree-uh MITCH-ell-ee-eye
(Fabaceae – the pea family)
subfamily: Faboideae – the bean subfamily
common name: Yellow Rattlepod
Crotalaria is derived from the Greek κροταλον (krotalon) , a rattle or castanets. You merely have to shake a plant bearing ripe pods to understand why. Mitchellii is named for Sir Thomas Livingstone Mitchell (1792–1855). This Scottish-born army officer, Surveyor-General of NSW from 1827, was not only a surveyor, but a geologist, botanist, artist and writer; as well as all this, he was one of the greatest of our early explorers. The books he wrote about his exploratory journeys were full of fascinating detail, and were very popular, not only in the colony, but also ‘at home’ in Britain. He explored extensively and mapped most of the Murray-Darling system, what is now western Victoria, and central Queensland. There are many plants named after him, most of which he had discovered on his expeditions and described and illustrated in his journals.
To give the Yellow Rattlepod found on Magnetic Island its full name, it is Crotalaria mitchellii ssp. mitchellii. There is a second subspecies, ssp. laevis, which has longer leaves than ours, but, as far as I can tell it is found only in north-eastern NSW, north of the Hunter River. Ssp. mitchellii is found along much of the Queensland coast, on many of the off-shore islands, and in inland Queensland in the headwaters of the Darling River around the Roma and Mitchell areas.
The Yellow Rattlepod is an erect perennial shrub, with typical pea flowers growing in erect racemes 8 – 20 cm long. The stems are pubescent (occasionally glabrous), the simple leaves usually elliptic to narrow-elliptic or obovate, 4 – 8 cm long and 1 – 4 cm wide, their upper surface glabrous and more or less glandular, the lower surface more or less pubescent, with stipules 1.5 – 5 mm in length. The racemes are crowded, with up to about 40 flowers. The flower pedicels are 1 – 3 mm long, the calyx 2 – 6 mm long and pubescent. The corolla is about 1 cm long, the wings shorter than the keel; the keel incurved at the middle; the beak about 6 mm long, twisted at the apex. As mentioned earlier, the flowers are yellow, usually with reddish to reddish brown streaks on both sides of the petals, although in this colony quite a number of the plants bear flowers that have few or no streaks on the petals.
The seed pods are up to 4 cm long, green, ripening to a blackish brown. All the pods I have examined contained 16 – 19 dimpled seeds, approximately 2 mm in diameter, that ripen to a darkish brown colour.
The various Crotalaria species are food plants for several caterpillars, including those of:
Photographs taken in Picnic Bay 2012
Page last updated 17th March 2018