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: cathead, devil's thorn, doublegee, prickly 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)	Australia (continental)		Hafliger, Toni J./Wolf, Matthias (1988) (p. 272)
China China	China (People's Republic of)		Hafliger, Toni J./Wolf, Matthias (1988) (p. 272)
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	Taiwan Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 141)

Additional information:
Fact sheet from the Government of Queensland, Australia. (PDF format).

Additional online information about Emex australis is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Emex australis as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Emex australis may be available from the Germplasm Resources Information Network (GRIN).

References:

Hafliger, Toni J./Wolf, Matthias. 1988. Dicot weeds, vol. 1. CIBA-GEIGY Ltd., Basle, Switzerland. 335 pp.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

Hussey, B. M. J./Keighery, G. J./Cousens, R.D./Dodd, J./Lloyd, S. G. 1997. Western weeds, a guide to the weeds of Western Australia. Plant Protection Society of Western Australia.

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

Parker, James L./Parsons, Bobby. 2012. New plant records from the Big Island for 2010-2011. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2011. Part II: Plants. Bishop Museum Occasional Papers. 113:65-74.

Swarbrick, John T. 1997. Weeds of the Pacific Islands. Technical paper no. 209. South Pacific Commission, Noumea, New Caledonia. 124 pp.

Tassin, Jacques. 2005. Jacques Tassin (IAC-CIRAD), personal communication.

Thistleton-Dyer, W. T. 1912. Flora Capensis: Being a systematic description of the plants of the Cape Colony, Caffraria, & Port Natal. Vol. V., sec 1. Acanthaceae to Proteaceae. Reeve & Co.

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

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.