Complete Name : Oxalis pes-caprae L.
Taxonomy : Magnoliophyta » » Eudicotyledonae » Oxalidales » Oxalidaceae » Oxalis pes-caprae
Authors : Phil Lambdon
Last Updated : November 3rd, 2006

Bermuda buttercup (U.K.), soursob (Australia), yellow sorrel, sourgrass, sour sorrel (South Africa) .

Bolboxalis cernua - (Thunb.) Small
Oxalis cernua - Thunb.
Oxalis cernua - Thunb.
Oxalis libica - Viv.
Oxalis pleniflora - Lanfranco

A short perennial herb forming large clonal colonies reproducing by annual bulbs. Flowering takes place between January and March, and is synchronous across the colony, producing spectacular displays of 1-5 pedicels with large cup-shaped bright yellow flowers with 5 yellow petals. Plants die back by late spring.

• Dispersal Mechanisms
  • The bulbs are dispersed by agricultural activity. They are also washed along gullies in rain or stream water.
• Reproduction
  • It is a heterostylous species, with at least three forms known globally. The forms are not easily cross-pollinated and are not self-compatible. Only the short-styled form is common in Europe, which means that plants do not produce seeds and must rely on vegetative reproduction.
• Known Predators/Herbivores
  • Mammals may graze the leaves and rodents consume bulbs.
    Outside Europe, the noctuid moth Klugeana philoxalis Geertsema is a specialist feeder on Oxalis species, and the parasitic plant Orobanche ramosa L. (branched broomrape) widely uses it as a host in the Mediterranean.
• Resistant Stages (seeds, spores etc.)
  • Propagated by bulbs produced in the axils of long, white rhizomes.

• Native (EUNIS Code)
  • Similar to European habitats.
• Habitat Occupied in Invaded Range (EUNIS Code)
  • Often extremely abundant in cultivated areas, especially where there is some shade from trees, such as olive and citrus groves or vineyards. Bulbs are often spread into secondary habitats that have some degree of disturbance such as riverbeds, ditches, dunes, ruderal areas, screes and degraded Mediterranean shrublands. C3: Littoral zone of inland surface waterbodies, F6: Garrigue, FA: Hedgerows, FB: Shrub plantations, H2: Screes, I1: Arable land and market gardens, I2: Cultivated areas of gardens and parks, J2: Low density buildings, J5: Highly artificial man-made waters and associated structures.
• Habitat Requirements
  • Prefers warm, light soils and remains sensitive to frost, which limits the distribution to southern Europe and below 700 m. Abundance often declines following the cessation of cultivation, although it may persist for some years in fallow or abandoned fields.

Oxalis pes-caprae was first brought to Europe (London) in 1757 and reached habitable Mediterranean areas via Sicily in 1796, Sardinia by 1859 and Crete by 1883. Early introductions were generally as ornamental plants, but it is no longer common in cultivation and subsequent spread has been through soil movement in agriculture, horticulture and gardening.

• Native Range
  • Cape region of South Africa
• Known Introduced Range
  • Has spread widely across southern Europe, North Africa and southwest Asia, particularly the Mediterranean region, but also extends to Pakistan and India. Has been recorded throughout Australia, the South Island of New Zealand, Japan and China. In the Americas, it is present in California, Arizona and Florida, and also from western South America.
• Trend
  • Stable, but may expand northwards in Europe due to global warming.

known distribution area (in CGRS grid squares; in countries; along coast)

	eradicated
	extinct
	not present; eradicated
	native distribution range in CGRS grid squares
	native range
	assumed native range
	infrequent distribution
	key distribution area
	not established

• Ecosystem Impact
  • It can suppress other ruderal weedy species. This is a serious problem where the arable flora is of conservation value, as over much of the Mediterranean old fields.
• Health and Social Impact
  • The massive floral displays in spring attract tourists to the Mediterranean.
• Economic Impact
  • The leaves contain large quantities of toxic oxalates, and in grassy areas the species can therefore be a danger to livestock. Significant losses of cattle and sheep have been recorded from some pastoral regions (e.g. Sardinia and Menorca). In annual crops, it can be a significant pest, reducing yields and becoming a nuisance during harvesting. Where olives are hand-picked from the ground, the foliage interferes with visibility and snags netting. Under certain circumstances there may be some agronomic benefit to infestations, in that they prevent the establishment of other weeds leaving the soil bare by summer, and the flowers provide forage for honeybees.

• Prevention
  • Prevention of soil contamination is essential.
• Mechanical
  • Grazing by pigs or turkeys, which consume the bulbs, may sometimes be practical. Soil ploughing in January can reduce plan growth and bulb production.
• Chemical
  • Pre-emergence treatments with glyphosate or sulphonyl urea-based herbicides (e.g. chlorosulfon, metsulfuron-methyl, triasulfuron, oxyfluorfen) are generally effective, although these must be used in moderately large doses in order to not affect crop performance or the native flora. It is resistant to certain classes of chemical such as dinitroanilines.
• Biological
  • None.

The following contributors have provided records in the DAISIE database for this species.

The following experts registered themselves as having knowledge about this species or its family.

Click here to search google images
Click here to search google scholar

Clarke GH (1934) Important weeds of South Australia No. 9-Soursob. Oxalis cernua, Thunb. Journal of the Department of Agriculture, South Australia 38:481-505

Marshall G (1987) A review of the biology and control of selected weed species in the genus Oxalis - Oxalis stricta L, Oxalis latifolia Hbk and Oxalis pes-caprae. L Crop Prot 6:355-364

Peirce JR (1998) Oxalis pes-caprae L. In: Panetta FD et al. (ed) Biology of Australian Weeds. R.G. & F.J. Richardson, Melbourne, Australia, pp141-156

Vilà M., I. Bartomeus, I. Gimeno, A. Traveset y E. Moragues. 2006. Demography of the invasive geophyte Oxalis pes-caprae across a Mediterranean island. Annals of Botany 97:1055-1062

Chawdhry MA, Sagar GR (1973) An autoradiographic study of the distribution of 14C labeled assimilates at different stages of development of Oxalis latifolia H.B.K. and O. pes-caprae L. Weed Research 13: 430-437

Chawdhry MA, Sagar GR (1974) Dormancy and sprouting of bulbs in Oxalis latifolia H.B.K. and O. pes-caprae L. Weed Research 14:349-354

Clarke GH (1934) Important weeds of South Australia No. 9-Soursob. Oxalis cernua, Thunb. Journal of the Department of Agriculture, South Australia 38:481-505

Galil J (1968) Vegetative dispersal in Oxalis cernua. American Journal of Botany 55:68-73.

Gimeno I, Vilà M, Hulme P (2006) Are islands more susceptible to plant invasion than continents? A test using Oxalis pes-caprae in the western Mediterranean. Journal of Biogeography 33(9):1559-1565

Lane D (1984) Factors affecting the development of populations of Oxalis pes-caprae L. Weed Research 24:219-225.

Pütz N (1994) Vegetative spreading of Oxalis pes-caprae (Oxalidaceae). Plant Systematics and Evolution 191:57-67

Vilà M, Gimeno I (2006) Potential for higher invasiveness of the alien Oxalis pes-caprae on islands than on the mainland. Plant Ecology 183:47-53

Vilà M, Tessier M, Suehs CM, Brundu G, Carta L, Galanidis A, Lambdon P, Manca M, Médail F, Moragues E, Traveset A, Troumbis AY, Hulme PE (2006) Regional assessment of the impacts of plant invaders on vegetation structure and soil properties of Mediterranean islands. Journal of Biogeography 33:853-861