Oxalis pes-caprae L., Oxalidaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Oxalis cernua Thunb.

Common name(s): [more details]

Chinese: huang hua cu jiang cao

English: African woodsorrel, Bermuda buttercup

Habit:  herb

Description:  "Perennials, 5-15 (-40) cm tall, acaulescent, sparsely pubescent; bulb with white fleshy contractile root and a slender vertical stem rising to soil surface; underground stem and soil surface crown bearing numerous small bulbils and scales. Petiole 3-10 cm, erect to spreading; leaflet blades obcordate, 0.8-2 x 1.2-3.2 cm, slightly succulent, bright green often with dark purple spots, glabrous, apex deeply emarginate. Umbellate cymes with 3-20 flowers; peduncle 2 x as long as petioles. Flowers 2-3 cm across, nodding. Sepals lanceolate, 2.5-4 x ca. 1 mm, apex with a pair of orange calli. Petals deep golden yellow, obovate. Capsule long terete, pubescent, very rarely formed"  (Flora of China online).

Habitat/ecology:  "Forests, grasssland, riparian habitats, coastal beaches, disturbed sites.  A highly variable species with more than 30 naturalized variants found in Australia, differing mainly in their leaflet markings.  The plant forms extensive, almost pure stands and spreads rapidly.  Although an important agricultural weed, it invades natural plant communities and displaces native plants by the dense stands"  (Weber, 2003; p. 294). 

In New Zealand, "waste places in and around settlements, disturbed soil on roadsides, cultivated soil, often forming dense stands and a serious garden weed, occasionally in open pockets in scrub on cliffs and banks"  (Webb et al., 1988; p. 921).  In Australia, "widespread, in gardens and orchards, along roadsides and arable land"  (NSW PlantNET).  "In Chile this species grows in the following environmental conditions:  Low altitude, interior valleys; coastal mountains, 500-2000 m; coastal areas, 0-500 m. Somewhat dry areas where the drought may last 3-5 months, precipitations of 400-800 mm. are concentrated in winter; humid areas, with almost constant rainfall, short dry periods are possible (generally not longer than 1 month). Fully exposed to the sun, level areas or slopes facing north"  (Chileflora).

Propagation:  "The plant produces bulblets abundantly which easily break off and are the main propagule for spread"  (Weber, 2003; p. 294).

Native range:  Namibia and South Africa (Cape Province)  (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive cultivated	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 556)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	New South Wales	introduced invasive	National Herbarium of New South Wales (2011)
Australia Australia (continental)	Northern Territory	introduced invasive	National Herbarium of New South Wales (2011)
Australia Australia (continental)	Queensland	introduced invasive	National Herbarium of New South Wales (2011)
Chile (continental) Chile	Chile (Republic of)	introduced	Belov, Michail (2011)
China China	China (People's Republic of)	introduced invasive cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2011) "Cultivated grounds, open habitats; low elevations. Naturalized at least in Fujian but cultivated elsewhere in S. China and very likely to escape and spread vegetatively.  This species is cultivated as an ornamental in at least Hubei, Shaanxi, and Xinjiang".
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 185)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 921)
United States (west coast) United States (west coast states)	USA (California)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011) Arizona
United States (continental except west coast) United States (other states)	USA (Florida)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Comments: 

Physical:  "Individual scattered plants can be dug out, all bulbs and bulblets need to be removed to prevent recolonization.  Constant weeding before bulblet formation may weaken the plant".

Chemical:  "Chemical control includes spraying 2,4-D, glyphosate, fenoprop, or chlorsulfuron"  (Weber, 2003; p. 294).

Additional information:
Weed alert from The Nature Conservancy.
Invasive species profile from the Global Invasive Species Database.
Fact sheet from University of California IPM Online.
Photos and other information from Chileflora.

Additional online information about Oxalis pes-caprae is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Oxalis pes-caprae as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Oxalis pes-caprae may be available from the Germplasm Resources Information Network (GRIN).

References:

Atkinson, Rachel/Sawyer, John. 2011. Naturalized species in the Juan Fernández Archipelago, Chile. Unpublished spreadsheet.

Belov, Michail. 2011. Chileflora (online resource).

Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido. 2006. Nouveau catalogue de la flore vaculaire de l'archipel Juan Fernández (Chile) [Nuevo catálogo de la flora vacular del Archipélago Juan Fernández (Chile)]. Acta Bot. Gallica 153(4):399-587.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

National Herbarium of New South Wales. 2011. PlantNet: New South Wales Flora online. The Plant Information Network System of the Botanic Gardens Trust Version 2.0. Online resource.

U. S. Government. 2011. Integrated Taxonomic Information System (ITIS) (on-line resource).

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).