South Australia

Sturt's Desert Pea or Swainsona Formosa

Floral Emblem of South Australia

Sturt's Desert Pea, Swainsona formosa, was adopted as the floral emblem of South Australia on 23 November 1961, using the name Clianthus formosus.

This species, a member of the pea family, Fabaceae, is confined to Australia, where it occurs in all mainland States except Victoria. The original collection was made in 1699 by William Dampier on Rosemary Island in the Dampier Archipelago where he collected a specimen from:

"a creeping vine that runs along the ground ... and the blossom like a bean blossom, but much larger and of a deep red colour looking very beautiful".

This specimen is now housed in the Sherardian Herbarium, Oxford. The species was for many years included in the genus Clianthus now thought to be confined to New Zealand.

Captain Charles Sturt (1795-1869) noted the occurrence of Swainsona formosa in 1844 while exploring between Adelaide and central Australia, and the common name, Sturt's Desert Pea, commemorates a notable explorer of inland Australia, as well as indicating the plant's habitat and family. Sturt's journal, Narrative of an Expedition into Central Australia, refers several times to the beauty of the desert pea in flower and the harsh nature of its habitat, and notes that beyond the Darling River:

"we saw that beautiful flower the Clianthus formosa [sic] in splendid blossom on the plains. It was growing amid barrenness and decay, but its long runners were covered with flowers that gave a crimson tint to the ground".

The genus name Swainsona honours Isaac Swainson who maintained a private botanic garden at Twickenham near London about the year 1789. The specific name formosa is Latin for 'beautiful'. The original author of the species was the Scottish botanist, George Don (1798-1856).

In its natural habitat Sturt's Desert Pea is a perennial plant with silky grey-green pinnate foliage arising from prostrate stems. The leaves and stems are covered with downy hairs. The flowers are about 9 cm long and arranged in clusters of six to eight on short, thick, erect stalks. The petals are usually blood red or scarlet with a glossy black swelling or 'boss' at the base of the uppermost petal, the standard. Other colour forms range from white to deep pink, either with or without a black boss, and rarely a bicoloured form, in which the standard is scarlet and the other petals, the wings and keel, are white tipped and edged with scarlet. The fruit is a legume about 5 cm long which splits at maturity releasing several flat kidney-shaped seeds.

Sturt's Desert Pea occurs in arid woodlands and on open plains, often as an ephemeral following heavy rain. It is able to withstand the marked extremes of temperature experienced in inland deserts, and light frosts are tolerated by established plants

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