Swainsona is part of the family Fabaceae. The genus consists of perennials and subshrubs. There are around 50 species in the Swainsona genus with all but one being endemic to Australia. The plants are legumes and have small racemes or spikes bearing ridged pea-flowers. The flowering season varies depending on the species with those in very arid areas only bursting into bloom after the onset of rain.
Generally the small flowers are red or pink but white and mauve also occur. The foliage usually consists of many small, grey-green leaflets which are covered with fine, downy hairs.
Swainsona formosa is also known as Clianthus dampieri and/or C.formosus and has the common names of Sturt’s desert pea, glory pea and Sturt’s pea. This magnificent plant is low-growing, reaching only 30cm in height but with a spread of some 4 metres. It is a sprawling annual (or short-lived perennial) which is found in all states bar Victoria and Tasmania. The spectacular flower of Sturt’s desert pea may reach 8cm in length and is a brilliant rich red with a shiny black centre. This striking species is the floral emblem of South Australia. The silky, pinnate leaves are a soft, greyish green and the flowers appear in clusters of 5 to 6 blooms. The flowering season lasts from winter through to summer and the plant is a favourite with birds. However it has a reputation as being difficult to grow. A dry climate, good drainage and a sunny position are non-negotiable with this plant which is now available in a grafted version.
Much taller is Swainsona sejuncta which grows to 1.2 metres. It is endemic to eastern Australia and is rarely found in domestic gardens. The flowers appear in a range of colours from yellow and orange through to pink and white. It requires a light but very well-drained soil.
Swainsona galegifolia (Darling Pea) is endemic to inland New South Wales and Queensland. It is a long-living shrubby perennial that is easy to cultivate and has a very long flowering season. The branches have fine pinnate leaves to ground level. The smooth, greyish leaves give a graceful outline to the bush. The flower spikes may be 15cm long and held on long stems. The sturdy pea-flowers may reach 2.5mm across. Colours range from pure white, through clear pinks and mauves to a striking magenta crimson. The flowers are followed by balloon-like pods which often have a pinkish tinge.
Swainsona maccullochiana, also known as the Ashburton pea, is from Western Australia and grows to 2 metres. It is an annual and has ferny, pinnate leaves. The heads of rose-pink pea-flowers appear mainly from November to February. This is an attractive species which likes a sunny, well-drained position.
Swainsonas do best in a mild climate in full sun. Most do not tolerate frosts although some can cope with very light frosty conditions. Species native to very arid regions prefer a dry winter while others need to be continually damp. All require good drainage.