Swainsona formosa (Sturt's desert pea)
Sturt's desert pea has striking, blood-red flowers with bulbous black centres, and is the South Australian floral emblem.
About this species
Sturt's desert pea was found in 1699 by the English explorer William Dampier (1652-1715) in the dry sandy islands of Dampier’s Archipelago, north-west Australia. The English botanist Allan Cunningham collected it in the same locality in 1818. Specimens from around that area were also collected by Benjamin Bynoe, the surgeon on the voyage of HMS Beagle.
The striking and unusual flowers have uniform crimson petals, broken up by a glossy purple-black disc on the standard petals. The common name honours the English explorer Charles Sturt, who recorded seeing large quantities of the flowers whilst exploring central Australia in 1844. The name Swainsona formosa was published by Joy Thompson in 1990, after studies showed that its similarity with Clianthus puniceus (lobster claw from New Zealand) was superficial, the flowers of both species being adapted for pollination by birds. The generic name Swainsona honours the English botanist Isaac Swainson (1746-1812), who was famous for his botanic garden at Twickenham.
Geography & Distribution
Widespread in dry parts of Western Australia, South Australia, New South Wales and the southern part of the Northern Territory, it has also been recorded in Queensland.
Herbarium specimen of Swainsona formosa collected in South Australia in 1926 (Image: RBG Kew)
A horizontally-lying or ascending, herbaceous plant that is glaucous (bearing a waxy bloom), and covered with long, whitish, silky hairs. The stems are slightly angular and tinged with red. The leaves have petioles (leaf stalks), are borne alternately on the stem and are divided into about 16 leaflets. There is a pair of large stipules (leaf-like appendages) at the base of each petiole. The peduncles (inflorescence stalks) are erect, and each bears a racemose umbel of four to six very large flowers (about 90 mm long), each on a drooping pedicel (flower stalk). The calyx is hairy and comprises a tube and five angular teeth or lobes. The corolla is bright red. The standard is very large, reflexed backwards from the base presenting its inner surface forwards, and exhibiting a prominent two-lobed projection at the base of the glossy disc-like lower portion of the petal. This is purplish-black, by contrast with the red colour of the rest of the petal blade. The wing petals are much shorter than the standard, whereas the keel petals are longer. There are nine united stamens (the male organs of the flower) and one free stamen. The hairy ovary (containing ovules which develop into seeds after fertilisation) gradually tapers into the long slender style.
In the wild, the flowers can be red through to pink or yellow, and albino forms have been recorded.
Illustration from Curtis's Botanical Magazine
Illustration of Swainsona formosa by W. Fitch in Curtis’s Botanical Magazine.
This illustration was drawn by W. Fitch from a specimen from the greenhouse of Messrs. Veitch and Sons, Exeter, and King’s Road, Chelsea, where its splendid blossoms were produced in March 1858.
Curtis’s Botanical Magazine (Editor: Martyn Rix) provides an international forum of particular interest to botanists and horticulturists, plant ecologists and those with a special interest in botanical illustration.
Now well over two hundred years old, the Magazine is the longest running botanical periodical featuring colour illustrations of plants. Each four-part volume contains 24 plant portraits reproduced from watercolour originals by leading international botanical artists. Detailed but accessible articles combine horticultural and botanical information, history, conservation and economic uses of the plants described.
Published for the Royal Botanic Gardens, Kew by Wiley-Blackwell Publishing.
See the Wiley-Blackwell Subscription Information page for rates (for both print and online).
Threats & Conservation
Sturt's desert pea is not considered to be at risk in the wild, but it is protected in South Australia, where collection of the flowers or plants on Crown Land is illegal without a permit.
Samples of seed of Swainsona formosa have been stored in Kew’ s Millennium Seed Bank as an ex situ conservation measure.
Australian Aborigines eat the roasted seeds, or make cakes by grinding the seeds and then baking them. However, the seeds contain trypsin inhibitors. Because trypsin is an essential enzyme which breaks down proteins during digestion, these seeds may not be an ideal source of nourishment.
Swainsona formosa was adopted as the South Australian floral emblem in 1961, and is an iconic flower in Australia. Its flowers are used for decoration by Australian Aborigines, and it appears in both traditional and more modern artwork. It is often photographed and has featured in prose and verse, and appears in some Aboriginal legends.
Millennium Seed Bank: Seed storage
Kew's Millennium Seed Bank Partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Description of seeds: Average 1,000 seed weight = 7.2 g.
Number of seed collections stored in the Millennium Seed Bank: Two.
Seed storage behaviour: Orthodox (the seeds of this plant survive drying without significant reduction in their viability, and are therefore amenable to long-term frozen storage such as at the MSB)
On the first exhibition of Swainsona formosa at the Horticultural Society in 1858, a silver medal was awarded to Messrs. Veitch and Son.
Sturt's desert pea has a reputation for being difficult to cultivate in the damp summers of northern Europe, because the roots are killed by various fungal diseases, such as Pythium root rot. Success has been achieved by grafting the seedlings onto young plants of Colutea arborescens or Clianthus puniceus at the cotyledon stage, and then growing them in a hanging basket. An alternative method is to plant the seeds in deep pots or tall drainpipes containing a very sandy soil, with a 3 cm covering of pure sand, and to water them carefully with soluble fertiliser.
This species at Kew
Sturt's desert pea is grown in the Tropical Nursery at Kew. Pressed and dried specimens are held in the Herbarium and made available to researchers by appointment. The details of one of these specimens, including an image, can be seen in the on-line Herbarium Catalogue.
Australia Landscape - Kew at the British Museum
In 2011, Kew and the British Museum brought to the heart of London a landscape showcasing the rich biodiversity of Australia, and how these fragile systems are under threat from land usage and climate change.
Swainsona formosa (Sturt's desert pea) was one of 12 star plants featured in the Landscape, which took you on a journey across a whole continent, from eastern Australia’s coastal habitat, through the arid red centre, to the western Australian granite outcrop featuring unique and highly endangered plants.
Australia Landscape was part of the Australian season at the British Museum.
Supported by Rio Tinto.
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