Patersonia fragilis, commonly known as swamp iris[2] or short purple-flag,[3] is a species of flowering plant in the family Iridaceae and is endemic to eastern Australia.

[15] This plant grows to a maximum of 1.5 metres in height and is often surrounded by empty ground where there is a common absence of large shrubs and trees.

[15] Patersonia fragilis can be propagated from seed but requires a constantly damp soil similar to its natural habitat.

[3] The wet vegetation communities of Patersonia fragilis may be subject to plant pathogens Phytophthora cinnamomi and myrtle wilt, both naturally occurring in the wetland regions of South Australia.

[16] In areas receiving above 600mm of rainfall per annum, the roots of P. fragilis may be invaded by Phytophthora that is a soil-borne fungal pathogen.

[16] Additionally, if the habitat of P. fragilis is situated close to a deforested site, there is a chance for myrtle wilt infection to the plant.

[16] Commonly caused by the naturally occurring wind-borne fungi known as Chalara australis, P. fragilis can be infected if it possesses any open wounds in its stem.