Family: Oxalidaceae Form: Herb / Shrub Origin: Cosmopolitan, but centres of diversity in South Africa and South America Weed Type(s): Quarantine Weed, Naturalised, Garden Escape, Environmental Weed

Photo: T. Rudman, DPIWE Tas

Notes: The genus Oxalis includes over 800 species of annual or perennial, stemmed or stemless, herbs and shrubs, often with underground bulbs or tubers. A few are aquatic species. Of the thirty species of Oxalis in Australia, twenty are naturalised and many are existing or potential serious pests in various parts of the country. Twenty two species of Oxalis were listed in Victorian nursery catalogues between 1855 and 1889. Eleven species are described in Gardening Australia's Flora (2003) with acknowledgement that 'some of the world's worst weeds belong in Oxalis,…'

One species of concern in Victoria is Soursob, Oxalis pes-caprae which invades coastal heath vegetation, grassland, woodland and dry forest. It also occurs along roadsides, and in gardens, crops and pastures. It is distinguished by the three heart-shaped leaflets with or without stalks which fold in dull days or at night. Flowers are bright yellow in colour and open in sunlight and close at night. There are masses of underground bulbs which are spread by water, birds, in dumped garden waste and during cultivation.

References:

Randall, R. P. (2002). A Global Compendium of Weeds. R. G. & F.J. Richardson, Melbourne.
Csurhes, S. and Edwards, R. (1998). Potential Environmental Weeds in Australia. National Weeds Program, Environment Australia, Canberra.
Royal Horticultural Society (1992). Dictionary of Gardening. The Macmillan Press Limited, London.
Brookes, M. and Barley, R. (1992). Plants Listed in Nursery Catalogues in Victoria 1855 - 1889. Ornamental Plants Collections Association, Melbourne.
Blood, K. (2001). Environmental Weeds. A Field Guide for S E Australia, C. H. Jerram & Associates-Science Publishers, Mt Waverley Victoria.