A family mostly of perennial herbs that regrow annually from tubers, bulbs or corms. Leaves usually of three heart-shaped leaflets. The family consists of about 900 species, of which about 800 are in the genus Oxalis whose species are found mainly in South Africa and Central and South America. Western Australia has 14 species in one genus, of which 12 are naturalised. Oxalis caprina is a delicate, white-flowered plant found in shady situations beneath bracken and karri in high-rainfall areas of the lower south-west and south coast. It grows in clumps that produce slender stems to 8cm tall, bearing the nodding white flowers in autumn and winter.
Oxalis glabra
in a firebreak, PH
Oxalis compressa produces clusters or loose rosettes of stalked leaves that grow from a bulb. It bears clusters of bright yellow flowers in early spring on long, leafless stalks that are very similar to soursob, O. pes-caprae. It can be distinguished by its flattened, hairy leaf stalk. Known only from farmland at Toodyay, but possibly more widespread. Native of South Africa.
Oxalis
compressa
, RR
O.
corniculata
(yellow wood sorrel, creeping oxalis) is a highly branched
annual with a slightly fleshy taproot, producing slender
stems that creep horizontally, rooting at intervals and with
leaves along the stem. Small, yellow flowers in clusters of
one to six, on stalks arising from leaf axils. Flowers in
spring and summer, reproducing from seeds produced in
explosive, cylindrical capsules. Plants vary in their
hairiness, redness of stems and leaves, size and growth form
and may include
similar native species (e.g. the closely-related
O.perennans that has large flowers, woody stems and a tuberous
rootstock). A cosmopolitan weed common in lawns and garden
beds. Widespread throughout the lower half of Western
Australia.
O.
corniculata
, RC
O. corymbosa (was O. debilis var. corymbosa) (pink shamrock, lilac oxalis) is a weed of old gardens and wasteland in the Metropolitan area. Produces a dense tuft of lush, dark green leaves that arise from the bulb. Flowers two to six borne in a loose cluster from autumn to spring. Petals narrow, pink, lilac or yellow. Native to South America. O. depressa, a white flowered, red leaved species similar to O. purpurea, is established in the foredunes at Busselton. Likely to naturalise elsewhere. Native to South Africa.
O.
corymbosa
, RR
O. flava is a relatively uncommon species, recognised by its large, solitary, yellow flowers and fan-like leaves composed of four to seven narrow leaflets on a short stalk. Found occasionally on roadsides and old habitation sites, around Perth and in the Avon Valley. Flowers in late autumn, almost immediately after the first rains. Native to South Africa.
O.
flava
, RR
O. glabra (finger leaf oxalis) is a distinctive species with thin, upright stems, each bearing leaves along most of its length and a large, solitary pinkish purple flower (sometimes white) with a yellow throat. Flowering from late autumn to spring. Leaflets short and narrow. Common on heavy soils from Perth to York and scattered in the lower south-west, in disturbed woodland, paddock edges and along firebreaks and tracks. Native to South Africa.
O. glabra , JD
O. incarnata (climbing oxalis) is a delicate plant with pale pink flowers on slender stalks, held clear of the foliage. Leaves arising in clusters where the stem branches, with small bulbils in the leaf axils. Often found in the karri forest beside creeks and along tracks and roads. Native to South Africa. Flowers in winter and spring.
O.
incarnata
, GK
O. pes-caprae (soursob, sour grass) is a common weed with stalked leaves and many-flowered inflorescences on cylindrical stalks that grow from deeply placed tubers and bulbs. Leaflets often spotted or marked. The bright yellow flowers appear in late autumn and winter. A major weed of crops, pastures, orchards, gardens, roadsides, wasteland and disturbed native vegetation throughout the south-west. May cause oxalate poisoning in sheep. Native to South Africa.
O.
pes-caprae
, JD
O. purpurea (four o'clock, large flower wood sorrel, purple wood sorrel) is a distinctive species usually with prostrate leaves in a small rosette, arising from a bulb. Leaflets almost circular, often deep purple on underside. The entire leaf is sometimes reddish. Flowers appear from late autumn to spring, appearing singly at ground level, larger than in most other Oxalis species. Three colour forms are naturalised - the widespread weed of pastures is rose-purple, while less common are the mauve and white forms. All have a yellow throat. Widespread on heavier soils in the Metropolitan area and increasing as a weed of crops and pastures, roadsides and lawns throughout the south-west. Native to South Africa.
O.
purpurea, RR
Many other species of Oxalis have been cultivated and may persist around old settlements and cemeteries, including the following: O. bowiei, O. hirta and O. violacea.
O. hirta
, RR
