TARGET SPECIES – other alien species

Oxalis pes-caprae L.

Family: Oxalidaceae
Scientific name: Oxalis pes-caprae
Synonyms: Oxalis cernua Thunb.
Common name: Acetosella gialla
English name: Soursob, African wood sorrel, Bermuda buttercup, Buttercup oxalis
Brief description: A perennial herbaceous plant with scapes measuring 10-40 cm. Rhizome about 1-2 cm thick, and numerous bulbils of about 5-10 mm; heart-shaped, trifoliate compound leaves of about 1.5-2.5 cm, with an erect petiole of about 5-40 cm. 5-12 flowers per scape, in umbrella-shaped clusters; bright yellow petals about 10-25 mm; ellipsoidal or ovoid capsules about 8 mm. Seeds generally not visible.
Biology and ecology: A rhizomatose geohphyte that generally propagates vegetatively (bulbils) and only rarely from seeds. Blooms Jan-May. Present from sea level up to 600 m.
Country of origin: South Africa.
First record: Gennari, 1889.
Status in Sardinia: Established and invasive, occasionally cultivated as carpets of flowers.
Habitat in Sardinia: Fallow and cultivated fields, vegetable gardens, olive and citrus groves, roadsides, gardens, urban environments.
Nature of invasiveness: Exceptionally high production of bulbils.
EPPO category IInvasive alien (since 2006).
Negative impacts: The leaves contain oxalates that may be toxic for livestock, with cases of intoxication and death of cattle and sheep reported in the Mediterranean (e.g. Sardinia, Balearics). It is a pest species affecting annual crops and reduces yields, requiring specific eradication efforts. In a limited number of cases, it can have a positive impact as a herbaceous species that can help reduce soil erosion or for the production of honey.
Containment activities: Preventing bulbils from expanding outside the invaded areas. Bulbils are transported during farming operation or as part of soil erosion processes. Root balls should always be checked when re-potting plants in urban parks or orchards. Eradication (including manually) from plant nurseries.
General notes: It was cultivated in Sicily as early as 1796, but was only described as abundant in the second half of the 19th century. It generally propagates vegetatively (bulbils), and seed production was not observed until the early 20th century, albeit rarely, and perhaps as a result of secondary adaptation that has made it able to self-fertilize. It is the most widespread species of Oxalis in Sardinia.
Species sheet by Giuseppe Brundu & Ignazio Camarda CBV / UNISS

Main references:

• C. Stelletta, V. Di Marco Lo Presti, S.A. Mignacca, V. Aronica, E. Biasibetti, M.T. Capucchio, P. Zanghì, I. Vazzana, 2013. Intossicazione acuta da piante contenenti acido ossalico (Oxalis pes-caprae) in un gregge ovino: valutazioni cliniche ed anatomo-istopatologiche. ATTI XX Congresso Nazionale S.I.P.A.O.C., 26-29 settembre 2012, Siracusa, pag. 86.

• Camarda I., 1998. Considerazioni su alcune specie di antica e recente introduzione in Sardegna e la loro dinamica diffusione. Biocosme Mésogéen 15(1): 89-108.

• Gennari P., 1889. Florula di Palabanda. N. Giorn. Bot. Ital., n.s., 21: 28-34.

• 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.

• Pignatti, s. 1982. Oxalis L. In Flora d’Italia Edagricole, vol. 2, pp. 1-3.

• 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.

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