Pale-flowered Oxalis

Oxalis incarnata

Synonyms -

Family: - Oxalidaceae.

Names:

Oxalis is from the Greek oksos meaning sour and refers to the taste of the leaves and stems.
Incarnata is from Latin and means flesh coloured.

Other Names:

Climbing Oxalis.
Pale Wood Sorrel.

Summary:

Pale-flowered Oxalis is a delicate sprawling herb to 250 mm high with clusters of green leaves at the ends of the stems and single white to pale pink, trumpet shaped flowers held above the leaves. There are 10 stamens and 5 styles. The fruit is a narrow capsule. The leaves are produced annually and each is divided into 3 heart-shaped leaflets. Small bulbils are produced in the leaf axils.
Native to South Africa it is often a weed of woodland or Karri forest.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Mainly crowded at the ends of branches. Sets of 4-10 in a ring like arrangement (Alternate but appear to be whorled). Each leaf is composed of three leaflets (trifoliate).
Small bulbils are formed in leaf axils.
Stipules - taper into petiole.
Petiole - 10-50 mm long. Hairless.
Blade - of leaflets - Heart shaped, 6-10 mm long by 9-18 mm wide. Tip indented. Sides curved. Base tapering.

Stems:

Erect, branching, slender, 50-250 mm long. Hairless.
Flower stem - Slender, 45-110 mm long. Hairless.

Flower head:

Single flowered.

Flowers:

Pale pink to lilac, occasionally white, with a green to yellow tube. Bisexual, symmetrical (actinomorphic)
Ovary -
Sepals - 5. 6 mm long
Petals - 5, 14-22 mm long. White to pale purple or pale pinkish-purple and greenish at the base.
Stamens - 10 in 2 rings. Outer ring opposite petals.
Anthers -

Fruit:

None recorded in Australia.

Seeds:

None recorded in Australia. Tend to be sterile overseas.

Roots:

Rhizome 30-80 mm long.
Bulbs egg shaped, pointed, 15 mm long, brown outer surface.
Bulbils formed on rhizome and in leaf axils.

Key Characters:

Leaves appear to be whorled.
Leaflets obcordate, bilobed with lobes 5-9 mm wide.
Aerial stem and branches erect or ascending.
Bulbils formed on rhizome and in leaf axils.
Peduncles axillary
Petals white, pink to mauve, 13-22 mm long.

Adapted from B. J. Conn,

Biology:

Life cycle:

Usually has annual tops with a perennial rhizome and bulbs.

Physiology:

Reproduction:

By small bulbils formed in the leaf axils

Flowering times:

August to November in WA.
Mainly August to January and occasional to May in NSW.

Seed Biology and Germination:

Seed has not been recorded in Australia.

Vegetative Propagules:

Small bulbils that formed in the leaf axils.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by bulbils.

Origin and History:

Native to South Africa.
Escaped from cultivation as an ornamental garden plant.

Distribution:

NSW, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Prefers moist shaded situations.

Climate:

Mediterranean.
Medium to high rainfall areas.

Soil:

Wet areas and along water courses.

Plant Associations:

Karri forest.

Significance:

Beneficial:

Ornamental.

Detrimental:

Weed of gardens, water courses, wet areas and roadsides

Toxicity:

Not recorded as toxic but closely related species can cause oxalate poisoning.

Symptoms:

Treatment:

Legislation:

None.

Management and Control:

Avoid spreading bulbs with earth moving and garden waste.
It is rarely a problem in grazed or cropped areas.

Thresholds:

Eradication strategies:

Mowing and grazing are generally ineffective and manual removal very difficult.
Best control with herbicides usually occurs around the bulb exhaustion stage which is often just before flowering. Dig up plants and inspect the bulbs which should be shrivelled and the new bulb not formed. Bulbils on roots should be less than 1 mm round.
Sulfonylurea herbicides and diuron usually provide the best control.
For spot spraying, 0.1 g metsulfuron(600g/kg) or 0.2 g chlorsulfuron(750g/kg) plus 25 mL wetting agent in 10 L water applied when the plants are actively growing provides good control. Repeat this if regrowth appears.
100 mL glyphosate(450g/L) in 10 L of water when the plants are young and actively growing can be used where no residual action is desired.

50 mL diuron(500g/L) in 10 L of water will kill plants and leaves a soil residue to help control corms or seeds germinating after spraying. Diuron can damage many species of trees and native plants and should not be applied above the root zone of desirable plants or where water flows may take it to the root zone of desirable plants.
For broadacre spraying use 20 g/ha chlorsulfuron(750g/kg) plus 0.25% wetting agent. Logran and Spinnaker are also useful and generally cause less damage to native species where overall spraying is necessary.
It usually takes 3 or more years to achieve high levels of control.
300 mL/ha Spinnaker® controls O. purpurea in pasture and 50 g/ha Logran® controls O. glabra wheat. These products will probably also kill other Oxalis species.
Fumigation with metham sodium is useful for limited areas such as seed beds and glasshouses.

Herbicide resistance:

Biological Control:

None.

Related plants:

There are six Oxalis species that are native to Australia.
Bowie's Wood Sorrel (Oxalis bowiei)
Chilean Wood Sorrel (Oxalis perdicaria)
Coastal Oxalis (Oxalis radicosa) is an Australian native species.
Finger-leaf Oxalis (Oxalis glabra) is a herb with an erect thin leafy stem and single large flowers held above the leaves. The leaflets are small and narrower than those of the other species. The flowers are pink to purple (or occasionally white) with a yellow throat. It is a weed of heavier soils in disturbed woodland and occurs from Perth to York, south to Augusta and around Kojonup.
Fishtail Oxalis (Oxalis latifolia) has about 12 purplish pink flowers and fishtail shaped leaves.
Hairy Wood Sorrel (Oxalis hirta)
Large-flowered Wood Sorrel or Four O'clock (Oxalis purpurea) has rosettes of leaves that may be tinged purple on the underside, and arise from a bulb. The flowers occur singly and are usually pink to purple with a yellow throat but sometimes white with a yellow throat.
Native Oxalis (Oxalis perennans) similar to O. corniculata but is a native species that has yellow flowers, woody stems and a stout, tuberous, brown rootstock.
Pale-flowered Oxalis (Oxalis incarnata) is a delicate sprawling herb with clusters of green leaves at the ends of the stems and single white to pale pink flowers held above the leaves. It is often a weed of woodland or Karri forest.
Pink Bulb Soursob (Oxalis flava)
Pink Shamrock (Oxalis corymbosa or Oxalis debilis)
Shamrock Oxalis (Oxalis articulata)
Soursob (Oxalis pes-caprae) is a herb which grows from tubers and bulbs, with clusters of yellow flowers radiating from a tall stalk held above the tuft of long-stalked leaves. The leaflets sometimes have dark markings.
Yellow Wood Sorrel (Oxalis corniculata) is a creeping herb with much-branched and sometimes reddish stems that root at many points. Young stems usually very hairy. It has single flowers or small clusters of yellow flowers occurring among the leaves. Style is at the same level as the anthers.
Oxalis bifurca
Oxalis brasiliensis
Oxalis caprina
Oxalis compressa
Oxalis chnoodes is an Australian native species.
Oxalis depressa an environmental weed.
Oxalis exilis is an Australian native species often misidentified as O. corniculata. It has a white to brown carrot shaped rhizome, large yellow flowers with long styles that exceed the anthers
Oxalis lactea
Oxalis rubens is an Australian native species.
Oxalis violacea is often incorrectly identified as Oxalis latifolia.
Oxalis tetraphylla
Oxalis thompsoniae is an Australian native species.
No native Oxalis species have round tubers in WA.

Plants of similar appearance:

Clovers
Lotus
Medics
Trefoils

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P196. Photo.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 3. P22. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (2007). Western Weeds. A guide to the weeds of Western Australia. (Second Edition). Plant Protection Society of Western Australia, Perth, Western Australia. P204. Photo.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #735.14.

Moore, J.H. and Wheeler, J.R. (2008). Southern Weeds and their Control. (Second Edition). (South Coast NRM and Department of Agriculture and Food Western Australia). P110. Photos.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P415.

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.

Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P729. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 for more information.