Patersonia (purple flag) is a genus of flowering plants in the Iridaceae with about 20 species in Australia and several in the Malesian region. The genus name is a tribute to the first Lieutenant Governor of New South Wales in Australia, William Paterson.
They are perennials with basal leaves growing from a woody rhizome that in some species extends above ground to form a short trunk. The leaves are tough and fibrous, often with adaptations for conserving moisture, such as stomata sunk in grooves, a thickened cross-section, marginal hairs, and thickened margins.
The flowers appear from between a pair of bracts on a leafless stem. They have three large outer tepals that are usually blue to violet, and three tiny inner tepals. There are three stamens fused at the base to form a tube around the longer style, which bears a flattened stigma.
Several Patersonia species are grown as garden plants. They can be propagated by seed or by division.
There are about 19 species, including:
- Patersonia argyrea
- Patersonia babianoides
- Patersonia drummondii
- Patersonia fragilis - swamp iris, a plant of sandy coastal heathlands in south-eastern Australia; it has narrow, grey-green leaves and pale violet flowers close to the ground.
- Patersonia glabrata - leafy purple flag, bugulbi (Cadigal), a shrub up to 80 cm high with wiry, tangled stems.
- Patersonia graminea
- Patersonia inaequalis
- Patersonia juncea
- Patersonia lanata
- Patersonia limbata
- Patersonia lowii
- Patersonia macrantha
- Patersonia maxwellii
- Patersonia occidentalis, which grows up to 75 cm tall and has blue flowers. It is widespread in southern Australia.
- Patersonia pygmaea
- Patersonia rudis
- Patersonia sericea - silky purple flag, which has bracts covered in short, silky hairs. It is an east coast species in Australia, replaced by the closely related P. rudis and P. lanata in Western Australia and P. macrantha in the Northern Territory.
- Patersonia spirafolia
- Patersonia umbrosa, a species from Western Australia that has two colour variants, the typical blue-violet variety, and the yellow-flowered var. xanthina from the karri forests.
- Cooke, D. A. (1986). Patersonia. Flora of Australia 46: 13-26. Australian Government Publishing Service, Canberra.