Emex australis Steinh., Polygonaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results: 

Reject, score: 8 (Go to the risk assessment (Australia)).
High risk, score: 17 (Go to the risk assessment (Pacific)).

Common name(s): [more details]

English: Cape-spinach, cathead, devil's thorn, doublegee, prickly jack, southern three-corner-jack, spiny emex, three-corner Jack

Habit:  herb

Description:  "A herb; stem branched, 3 lin. in diameter, ribbed when dry, glabrous; leaves ovate or oval, with the outer basal angles rounded, obtuse, cuneate into the 2 in.-long petiole, 3 in. long, 2 in. wide, entire or obscurely crenate, glabrous; outer fruiting perianth 6 lin. long, less indented between the angles than in E. spinosa L., spines spreading; inner segments broadly ovate, mucronate, strongly reticulately nerved."

"This species differs from E. spinosa Campd. in the larger, less rugose outer fruiting perianth with longer spinescent segments, and the inner erect segments being broader and more rounded" (Thiselton-Dyer, 1912; pp. 481-481).

Habitat/ecology:  In New Caledonia, "espèce envahissante récoltée une seule fois et peut-être pas établie en Nouvelle-Calédonie" (MacKee, 1994; p. 116). In Western Australia, "a widespread agricultural and wasteland weed" (Hussey et al., 1997).

Propagation:  Seed

Native range:  Southern Africa (Hussey et al., 1997).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Parker, James L./Parsons, Bobby (2012) (pp. 72-73) Vouchers cited: J. Parker & R. Parsons BIED148 (BISH), R.A. Goff s.n. (BISH #63678), H. Kennedy & S. Ishikawa 3910 (BISH)
New Caledonia New Caledonia	New Caledonia Islands		Swarbrick, John T. (1997) (p. 92)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced invasive	Tassin, Jacques (2005)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced	MacKee, H. S. (1994) (p. 116) Voucher cited: MacKee 35455

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) Naturalised
Australia Australia (continental)	Australia (continental)	introduced invasive	National Herbarium of New South Wales (2013) South Australia, Victoria, Western Australia Naturalised
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 966) "Coastal areas, mainly in waste and cultivated land on light sandy soils, sometimes in rough pasture".
Taiwan Taiwan Island	Taiwan Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 141)

Control:  If you know of control methods for Emex australis, please let us know.