Cotula coronopifolia L., Asteraceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: bachelor's-button, brassbuttons, buttonweed, common brassbuttons, water buttons, water cotula

French: cotule, cotule à feuilles de sénebière

Spanish: botón de oro

Habit:  herb

Description:  "Ascending to erect, fleshy, glabrous annual or short-lived perennial up to 30 cm tall. Stems terete, branched from base and above, up to 25-(40) cm long, rooting freely from lower nodes. Leaves fleshy, alternate, apetiolate, linear, lanceolate or spathulate, entire, with few irregular large lobes, or shallowly 1-(2)-pinnatisect, usually perfoliate, rarely amplexicaul, (10)-15-80 mm long; leaves above becoming shorter, more triangular, less often divided and more often amplexicaul. Involucral bracts in 2-3 rows, 4-6 mm long. Capitula solitary, bright yellow, (6)-8-10-(13) mm in diameter; peduncles scarcely expanded at apex, solid, 2-7 cm long, c. 1 mm diameter; ♀ florets in 1 or < 1 row, pedicellate, with a corolla; ☿ florets numerous, subsessile, with flattened tubular corolla. Achenes all flattened, hairy on inner surface, glabrous on outer. Achenes of ♀ florets 1.5-2 x 1-1.2 mm; lateral angles with thick, corky, entire, marginal wings. Achenes of ☿ florets 1.1-1.2 x 0.5-0.6 mm; lateral angles thinly ribbed"  (Webb et al., 1988; p. 168).

Description from Flora of North America online.

Habitat/ecology:  Saline and freshwater marshes, swamp edges, streambanks.  A pioneeer plant of bare, wet and nutrient-rich soils, growing both in freshwater and brackish water habitats.  The plant is able to build up dense populations that crowd out native vegetation"  (Weber, 2003; p. 125).

In New Zealand, "Coastal sites, especially lagoons and swamps, also inland in wet sites and waste places"  (Webb et al., 1988; p. 168).  In New South Wales, Australia, "grows in damp, often saline disturbed communities; widespread"  (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. The plant grows in water or it has its roots within a permanent water course. This corresponds to marshes, bogs, water courses, lake and river shores. 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. Some shadow. Some protection against direct sunlight, some shadow from vegetation, filtering about 20-40% of light"  (Chileflora).

Propagation:  Seed.  "It is a prolific seed producer, and seeds are mainly dispersed by water.  Weeds remain viable for 1-2 years"  (Weber, 2003; p. 125).

Native range:  Namibia, South Africa (Eastern Cape, Gauteng, Northern Cape, Western Cape); naturalized elsewhere (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	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (pp. 460, 464, 552)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Santa Clara	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (pp. 460, 464, 552) Voucher cited: Danton B(446)403

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 (2013)
Australia Australia (continental)	Queensland	introduced invasive	National Herbarium of New South Wales (2013)
British Columbia (province of Canada) Province of British Columbia	Canada (British Columbia)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 190)
Mexico Mexico	Mexico (United Mexican States)	introduced	Flora of North America Editorial Committee, eds. (2013) Baja California
New Zealand New Zealand	New Zealand (country)	uncertain if introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 168)
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	introduced invasive	Belov, Michail (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (Oregon)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (California)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (west coast) United States (west coast states)	USA (Washington)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Canada Canada	Canada	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (continental except west coast) United States (other states)	United States (other states)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Alaska, Arizona, Maryland, Nevada Naturalized

Control:  If you know of control methods for Cotula coronopifolia, please let us know.