Patersonia fragilis

Swamp Iris, Short Purple-flag

Family: Iridaceae

A monocotyledonous, densely tufted, herbaceous perennial to 0.6 metres high by about 0.3 metres wide, with basal leaves growing from a woody rhizome. It is a native Iris.

It has a scattered distribution through near-coast areas and into the tablelands of NSW. The Australasian Virtual Herbarium records show that it extends into Queensland, as far as north of Rockhampton. It grows through most of the southern part of Victoria and into South Australia to Adelaide and Kangaroo Island. It also grows extensively around coastal Tasmania.

It is typically found in wet heathland, on sandy soils.

Patersonia spp. have simple leaves with parallel venation, which are typically heavily clustered on the rhizome. The leaves are tough and fibrous and have evolved to reduce water loss. In this species, leaves are linear and twisted, to greyish-green, to 80 cm long and only 0.6 cm wide with a biconvex to terete cross-section.

Patersonia spp. produce flowers from between a pair of bracts on a leafless stem or scape.
They have three large outer tepals that are usually blue to violet, and three tiny inner tepals (petals and sepals which cannot be allocated assuredly). Individual flowers open for less than one day, but many flowers are produced on the one stem.

In this species, the outer tepals are obovate to rhombic, to 25 mm long and 15 mm wide, pale violet to blue-violet with the inner tepals only 2 mm long, emerging from a tube of 3.5 cm long, occurring mainly from August to December.

Patersonia produce a capsule-fruit; three-celled and triangular in cross section with abundant seed. In this species, the capsule is cylindrical, to 30 mm long with seeds to 2.5 mm long, black and glossy.

In the garden

This species is known to be cultivated but may be a bit more difficult that some of the other dryland species.

Check with local native nurseries for availability or online.

It is an attractive plant for rockeries, water features and bog gardens when planted either singly or en masse.

It needs to grow in light and continually moist soils, in full sun to semi shade. Flowers open in the morning and close up by early afternoon.

It is reported to only tolerate dry conditions for less than a week. However, a boggy-sandy area in a garden may be very suitable.

This author has found plants with basal leaves look their best when planted in odd numbers, ie 1 or 3 or 5 etc. so consider this when planting.


Propagated is by seed which is very easy or by division.

Reproduces through bee pollination.

Other information

Patersonia is a genus of about 20 species, occurring in Australia, New Caledonia and other areas of the Pacific and Asia. Australia has 17 endemic species in Queensland, Victoria, Tasmania and South Australia. NSW currently has 3 species.

Patersonia grow in very fire-prone environments and can regenerate from the buried rhizomes or the seed bank.

Patersonia – named for William Paterson (1755-1810) who was a Scottish soldier, explorer, botanist and the first Lieutenant Governor of New South Wales in Australia.

fragilis – Latin meaning ‘fragile’ – not certain what this refers to – perhaps the brittleness of the leaves or the texture of the flowers.

This species is not considered to be at risk of extinction in the wild.

Australian National Herbarium – Patersonia profile page

Yarra Ranges Council – Patersonia fragilis profile page

Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.

By Jeff Howes. Editing and additional text by Dan Clarke.