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Canavalia rosea (Sw.) DC. 1825
pronounced: kan-uh-VAY-lee-uh ROH-see-uh
(Fabaceae – the pea family)
subfamily: Faboideae – the bean subfamily
synonym: Canavalia maritima Thouars 1813
pronounced: kan-uh-VAY-lee-uh mar-ih-TEE-muh
common name: Coastal Jack Bean, Beach Bean, Seaside Bean
Canavalia is the Latinized form of the Malabar vernacular kanavali, the name for this genus of climbing herbs. Rosea is from the Latin roseus, rosy. In the synonym, maritima is from the Latin maritimus, belonging to the sea.
This is a mostly herbaceous vine that trails along beach dunes and coastal sand. The thick, fleshy stem can grow to 6 m or more in length, and more than 2.5 cm in diameter, though it is usually much thinner than that. The stem is rather woody near the base, and several branches radiate outwards, forming mats of light green semi-succulent foliage. The plant is quite capable of scrambling, up to a height of a couple of metres or so, over other vegetation when it gets further back from the coastal dunes. It has compound leaves with 3 thick, more or less rounded, leaflets, each about 5–8 cm long. The leaflets fold up under the hot sun in the middle of the day. The plant readily sets down roots at the nodes as it trails across beaches and dunes, the roots forming networks that help stabilize the sand.
The flowers are typical pea flowers, a purplish pink in colour, about 5 cm long and borne in erect spikes on long stalks. The plant blooms most of the summer, and sporadically through the rest of the year.
The pods are flat and about 10–15 cm long, and about 2.5 cm wide. They are prominently ridged and woody when mature. The seeds, usually about 6 per pod, float, and are distributed by ocean currents.
Coastal Jack Bean has a pan-tropical distribution, occurring naturally on seashores in the tropics and subtropics throughout the world. It was one of those plants collected in 1770 by Banks and Solander during the voyage of the Endeavour. It was collected at the Endeavour River (Cooktown).
The plant is used as a biomass cover crop in Third World countries, and in arid parts of Australia and Africa, where its amazingly quick growth quickly covers even the harshest soils. It is used to control soil erosion in many parts of the world.
The young pods and seeds are edible, and are used for food by the Aboriginal peoples of northern parts of Australia. Mature seeds must be boiled or roasted to make them edible, and I understand that the outer skin of the beans should be removed before they are eaten. The plant became an important food for Captain Cook and his crew during their Pacific voyages.
In some places, an infusion is made from the crushed roots and rubbed over the skin for rheumatism, general pain, skin disorders, and colds.
Seeds of this plant have been found in graves in Mexico and Peru, in sites dating from 300 BC to 900 AD. It is believed that the beans were used in magic and religious rituals, together with dried leaves.
Caterpillars of the Dark Cerulean butterfly Jamides phaseli feed on this plant.
Information about medicinal qualities of plants, or about their use as medicines, is for interest only, and is not intended to be used as a guide for the treatment of medical conditions.
Photographs taken on Nelly Bay beach 2009, 2012 and at Horseshoe Bay 2014
Page last updated 15th October 2016