Family: Oxalidaceae

Status: some species still promoted as garden plants despite their invasiveness.

Description:
Oxalis grows from a bulb and so is only visible above ground for only part of the year. Leaves consist of 3 leaflets, similar to clover. Flowers are shortly tubular with 5 petals. Most of the more colourful oxalis species do not produce seed in Australia.

Preferred habitat and impacts:
Appears mostly around towns and old farms, in cemeteries and on nearby roadsides, as they are garden escapees. They can form a dense groundcover, excluding native species, especially in shady sites.

Dispersal:
Dumping of garden waste spreads bulbs. Infestations gradually enlarge by the production of bulbils from the parent bulbs.

Look-alikes:
Native species of oxalis occur, but they are all yellow flowered, are generally low sprawling or creeping plants with flowers in groups of 1-4, with much smaller flowers than the introduced species. Those species of oxalis which are garden escapees generally have pink, purple or white flowers. There are some weedy yellow flowered oxalis as well. Soursob (Oxalis pes-caprae) is distinctive in having an erect habit, with a single flowering stem to 35cm high carrying up to 25 flowers. Oxalis corniculata is very difficult to distinguish from native oxalis species.

Control:
Small infestations can be dug out, but this should be done when soil is moist (though not too wet), to avoid leaving behind the bulbs, or the small bulbils which develop around the base of the parent bulb late in the season. Spraying is also effective, but may need to be repeated the following season.