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Scientific Name
Synonyms
Family
Common Names
Origin
Cultivation
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Legislation
Management
Similar Species
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Click on images to enlarge

large infestation (Photo: Sheldon Navie)

dense infestation (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit prior to flowering (Photo: Sheldon Navie)

stems and leaves (Photo: Greg Jordan)

close-up of leaf with three heart-shaped leaflets (Photo: Greg Jordan)

flowers (Photo: Sheldon Navie)

close-up of flower (Photo: Sheldon Navie)

close-up of flower from side-on (Photo: Greg Jordan)

white fleshy rhizomes with bulbils forming on them (Photo: Sheldon Navie)

young plant (Photo: Sheldon Navie)

Oxalis pes-caprae

Scientific Name

Oxalis pes-caprae L.

Synonyms

Oxalis cernua Thunb.

Family

Oxalidaceae

Common Names

African wood sorrel, African wood-sorrel, African woodsorrel, Bermuda buttercup, buttercup oxalis, Cape cow-slip, Cape cowslip, Cape sorrel, drooping wood sorrel, Englishweed, large yellow soursob, oxalis, shamrock, sorrel, sour grass, sour sob, sourgrass, soursob, soursobs, soursop, soursops, South African wood sorrel, variable wood sorrel, variable wood-sorrel, wild sorrel, wood sorrel, yellow flowered oxalis, yellow sorrel, yellow sour-grass, yellow-flowered oxalis

Origin

Native to southern Africa (i.e. South Africa and Namibia).

Cultivation

Soursob (Oxalis pes-caprae) was originally introduced into Australia as a garden ornamental. It is no longer deliberately cultivated, but is often seen as a weed of gardens.

Naturalised Distribution

Widely naturalised, particularly in the southern parts of Australia. It is common in eastern and southern New South Wales, Victoria, Tasmania, south-eastern South Australia and south-western Western Australia. Also occasionally naturalised in south-eastern Queensland and the southern parts of the Northern Territory, as well as in other parts of New South Wales, South Australia and Western Australia.

Naturalised overseas in Europe, tropical Asia, New Zealand and southern USA (i.e. California, Arizona and Florida).

Habitat

This species is most commonly found in temperate regions, but occasionally also inhabits semi-arid and cooler sub-tropical environments. It is a weed of gardens, parks, lawns, waterways, roadsides, disturbed sites, waste areas, pastures, grasslands, open woodlands, crops and orchards.

Habit

A long-lived (i.e. perennial) herbaceous plant with upright (i.e. erect) flowering stems usually growing 15-30 cm tall, but occasionally reaching up to 45 cm in height. It produces a rosette of leaves at ground level and underground stems (i.e. rhizomes), bulbs, bulbils and tubers. The aboveground stems and leaves are short-lived (i.e. annual) and die back each year.

Distinguishing Features

Stems and Leaves

The slender flowering stems are sparsely hairy (i.e. pubescent), leafless, and round in cross-section.

The leaves emerge from the top of an underground stem (i.e. rhizome) at or just below the soil surface. They are borne on long stalks (i.e. petioles) 5-22 cm long and consist of three heart-shaped (i.e. obcordate) leaflets. These leaflets (5-30 mm long and 4-35 mm wide) are mostly green in colour, sometimes bearing brown or purple-coloured markings, and fold downwards during darkness. They are hairless with entire margins and deeply-notched tips (i.e. emarginate apices).

Flowers and Fruit

The bright yellow flowers (25-40 mm across) are borne in loose clusters (each with 3-25 flowers) at the top of the stems on individual stalks (i.e. pedicels) up to 20 mm long. They are trumpet-shaped (i.e. tubular) in appearance with five broad overlapping petals (15-25 mm long) that are fused together towards their bases. These flowers also have five sepals, ten stamens and an ovary topped with five styles. They open only during sunny conditions and close again at night or during dull conditions. Flowering occurs mainly from early winter through to late spring (i.e. from May to November).

The short capsules are rarely formed in Australia.

Reproduction and Dispersal

This species most commonly reproduces via underground bulbs and bulbils (seeds are rarely produced in Australia). The cone-shaped (i.e. conical) bulbs are white, fleshy segments (8-30 mm long) covered in brown scales, while the bulbils are smaller and generally lack the brown covering of scales.

Bulbs and bulbils are most commonly spread by cultivation and other forms of soil movement. They are also dispersed to new areas in contaminated soil, in dumped garden waste, by water movement and by animals (e.g. birds).

Environmental Impact

Soursob (Oxalis pes-caprae) is a significant environmental weed in Victoria and South Australia and an environmental weed in Western Australia and New South Wales.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Similar Species

Soursob (Oxalis pes-caprae) is very similar to Oxalis compressa and relatively similar to creeping oxalis (Oxalis corniculata) and pink bulb soursob (Oxalis flava). These species can be distinguished by the following differences:

Soursob (Oxalis pes-caprae) is also relatively similar to several native species of oxalis (i.e. Oxalis chnoodesOxalis exilis,Oxalis perennans, Oxalis radicosa, Oxalis rubens and Oxalis thompsoniae). However, all of these species have aerial stems with upright (i.e. erect or ascending) or creeping (i.e. prostrate) branches. Their yellow flowers are also smaller, usually being less than 15 mm across.