Finger-leaf Oxalis is a small herb with an erect thin leafy stem and single large flowers held above the leaves. The flowers are single with five pink to purple (or occasionally white) petals and a yellow throat from May to August on a thin, erect stem above trifoliate leaves with finger-like leaflets. There are 10 stamens and 5 styles. The fruit is a narrow capsule. The tops are produced annually form underground bulbs and stolons.
Native to South Africa it is a weed of heavier soils in disturbed woodland and occurs from Perth to York, south to Augusta and around Kojonup.
Description:
Cotyledons:
Two.
First leaves:
Trifoliate
Leaves:
Alternate. Trifoliate with narrow leaflets. Few to many.
Stipules - Tiny or none.
Petiole - 7-40 mm long.
Blade - of leaflets - 8-14 mm long by 1-2 mm wide, narrow and heart shaped. 2 small warts. Tip indented, Sides parallel. Base tapering. Hairless on top.
Stem leaves - same as above.
Stems:
50-200 mm long. Usually unbranched. Tiny hairs or rarely hairless.
Flower stem - Up to 25-120 mm long. Thin with leaves along its length. Terminal or arising from leaf axils.
Flower head:
Single flowers on the ends of thin stems held well above the leaves
Bracts 3-5 mm long with a wart on the tip
Flowers:
Pink to purple or occasionally white, with a yellow throat and 5 overlapping petals.
Ovary - Superior, 5 celled. Hairy on the top half
Styles - 5, free, at the top of the ovary. Hairy.
Sepals - 5. 7 mm long, narrowly egg shaped, pointed tip, overlapping. Often with purple edges.
Petals - Pink or white with a yellow throat. 15-30 mm long. Tubular at the base with 5 overlapping widely spreading lobes.
Stamens - 10
Filaments - Sparsely glandular hairy. Long narrow, pointed teeth on the lower half.
Anthers - 10
Fruit:
Hairy on the inner surface.
Does not appear to be produced in WA.
Seeds:
Does not appear to set seed in WA.
Roots:
Egg shaped, pointed bulb, 5-9 mm long.
Bulbils on underground runners (stolons)
Key Characters:
Herb
Leaves divided into 3 very narrow, heart shaped leaflets
Stems erect and leafy.
Flowers, single with 5 pink to purple or white petals.
Adapted from Judy Wheeler
Biology:
Life cycle:
Perennial herb with an annual top
Physiology:
Reproduction:
Flowering times:
Autumn to spring in WA.
May to August in Perth.
Seed Biology and Germination:
Vegetative Propagules:
Underground bulbs and bulbils.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Spread by water flows, ants and in movement of contaminated soil.
Origin and History:
Native to South Africa.
Distribution:
WA.
Widespread in the Darling Ranges. From Bunbury to Augusta and inland to Narrogin and Toodyay.
Common on clayey soils but also occurs on sands and laterite soils
Plant Associations:
Woodland
Significance:
Beneficial:
Ornamental.
Detrimental:
Weed of roadsides, tracks, firebreaks.
Toxicity:
Contains oxalic acid but infestations are rarely dense enough to cause significant problems with stock.
Symptoms:
Hypocalcemia. Stiffness in walking, loss of control of hind quarters, inability to rise, trembling and muscular rigidity. In sheep that have died the hind legs are often stretched out to the rear, the head is stretched forward and there is a slimy discharge from the nose
Treatment:
Remove stock from infestation. Recovery may take several weeks.
Legislation:
Management and Control:
Very difficult to hand weed. Plant must be dug out otherwise the bulbs and bulbils break off in the soil. Glyphosate or sulfonyl urea herbicides provide high levels of control.
Mowing and grazing are ineffective
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.
Sulfonyl urea 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:
None reported.
Biological Control:
None.
Related plants:
Bowie's Wood Sorrel (Oxalis bowiei)
Chilean Wood Sorrel (Oxalis perdicaria)
Coastal Oxalis (Oxalis radicosa)
Fishtail Oxalis (Oxalis latifolia) is a larger plant.
Hairy Wood Sorrel (Oxalis hirta)
Large-flowered Wood Sorrel or Four O'clock (Oxalis purpurea) has a 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) a very similar native species that has larger yellow flowers, woody stems and a tuberous rootstock and is often confused with Yellow Wood Sorrel.
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. It has single flowers or small clusters of yellow flowers occurring among the leaves.
Oxalis bifurca
Oxalis brasiliensis
Oxalis caprina
Oxalis compressa
Oxalis depressa
Oxalis lactea
Oxalis violacea is often incorrectly identified as Oxalis latifolia.
Oxalis tetraphylla
No native Oxalis species have bulbs.
Plants of similar appearance:
Four O'clock (Oxalis purpurea)
References:
Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P190. Photo.
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #735.12.
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P494.
Moore, J.H. and Wheeler, J.R. (2002). Southern Weeds and their Control. P 96. 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 or www.herbiguide.com.au for more information.