Xanthium spinosum L., Asteraceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: Bathurst burr, dagger cocklebur, daggerweed, prickly burweed, spiny burweed, spiny clotbur, spiny cockleburr, thorny burweed

French: lampourde épineuse

Spanish: abrojo, cachurrera menor, cepacaballo, clonqui, concli, pegotes

Habit:  herb

Description:  "Much-branched, somewhat woody annual herb to 0.6 m tall.  Stems and most branchlets or the base of each leaf covered with 3-pronged spines. Leaves divided into irregular lobes, green above, paler below.  Flowers mainly in clusters in the axils of the leaves.  Fruits hard woody burrs, brown, covered with yellowish hairs and numerous hooked spines with 2 taller straight spines at the end"  (Smith, 2002; pp. 67-68).

"Spiny cocklebur is an erect, much branched annual that grows up to three feet high. It reproduces by seed. About one inch long spines are found in leaf axils and at stem nodes. The leaves are shiny dark green and hairy on the upper surface and downy beneath. The leaves are mostly three-lobed with the center lobe  much longer than the other two, and up to three inches long. The flowers are small, inconspicuous, and creamy green. The male flowers are found at the top of the stems and the female flowers are formed lower on the stems. The fruit is more or less an egg-shaped burr, up to one-half inch long, armed with numerous hooked spines, some with one or two straight terminal spines. There are two seeds per burr, flattened, three-eighths inch long and brown in color" (Washington State Noxious Weed Control Board).

Habitat/ecology:  "Mainly a pasture or meadow weed, the plant grows along roads and in disturbed areas, and abandoned fields; it is sometimes common around waterholes and along floodplains, canals, ditches, creek flats, river terraces, and other moist places (Holm et al., 1977; pp. 474, 477).  "Grows in a wide variety of habitats; often in disturbed areas such as roadsides, stockyards, bores and abandoned settlements" (Smith, 2002; pp. 67-68). "Spiny cocklebur is adapted to a variety of climates, hence its wide distribution. It is found in a wide variety of soil types growing in cultivated fields, wastelands, farm yards, flood plains, and along waterways" (Washington State Noxious Weed Control Board).

Propagation:  "The spiny fruit...adhere to wool, fur, clothing, hay bales, mud, etc. The fruits float and are readily dispersed by water. Fruits are also spread in contaminated pasture seed" (Smith, 2002; pp. 67-68). "Of the two seeds in each burr, one germinates the first spring or summer and the other does not germinate until the second or third year. Some seeds may remain viable for up to eight years" (Washington State Noxious Weed Control Board).

Native range:  South America (Smith, 2002; pp. 67-68).

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	Skottsberg, Carl (1953) (p. 225)
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) (p. 558)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más Afuera (Alejandro Selkirk Island)	introduced invasive	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (p. 558)
Fiji Fiji Islands	Viti Levu Island	introduced	Smith, Albert C. (1991) (p. 290) Voucher cited: DA L.13382. (Single specimen, present status unknown).
Kiribati Line Islands	Teraina (Washington) Island	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	introduced invasive	Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 476)

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	Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 476-477)
Australia Australia (continental)	Northern Territory	introduced invasive	Smith, Nicholas M. (2002) (p. 67)
Australia Australia (continental)	Queensland	introduced invasive	Smith, Nicholas M. (2002) (p. 67)
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 190)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 227) "Waste places, coastal sites, pasture, cultivated land, gardens".
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	native	Belov, Michail (2013)
United States (west coast) United States (west coast states)	USA (Oregon)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (west coast) United States (west coast states)	USA (California)	introduced	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)

Control: 

Physical:  "Single pants can be hoed".

Chemical:  "Chemical control is done by spraying plants with 2,4-D, MCPA or imazaquin.  Control measures should aim at preventing seed formation"  (Weber, 2003; p. 456).