Praxelis clematidea R.M. King and H. Rob., Asteraceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 25 (Go to the risk assessment)

Other Latin names:  Eupatorium catarium Veldk.

Common name(s): [more details]

English: praxelis

Habit:  herb

Description:  "Perennial (already flowering in its first season) 0.3-1 m tall, caudex woody, erect, branched, branches terete, angular, septate hirsute, laxly foliate, malodorous.  Internodes 3-16 cm long.  Petioles 0.3-2 cm long, blades ovate to rhomboid, 2.5-6 by 1-4 cm, septate hirsute and gland-dotted on both sides especially underneath, base rounded to cuneate, 3-nerved, margins coarsely dentate, teeth 5-8 on each side, acute, apex acute.  Inflorescence of many capitules in terminal, dense, corymbiform, few-headed cymes.  Pedicels septate hirsute, 2-10 mm long.  Involucre cylindrical campanulate, 7-10 by 4-5 mm.  Phyllaries in 4 or 5  series, yellowish with 3-5 green nerves, distally purplish, glabrous to distally appressed strigose, the outer ones smallest, lanceolate, apex acuminate, the inner linear, acute.  Flowers 25-30, somewhat purplish blue or lilac; corolla 3.5-4.8 mm long, shortly (4- or) 5-dentate.  Achenes 2-3 mm long, black, distally hispidulous; pappus bristles 15-40, white" (Veldkamp, 1999).

"The flowers are purplish-blue and the plant can be confused with billygoat weed (Ageratum houstonianum and A. conyzoides)."  (Csurhes and Edwards, 1998; p. 125).

Habitat/ecology:  Wet tropics; prevalent along roadsides, grasslands. Forms monospecific stands, excluding other vegetation. Prevalent up to 3050 m in South America,700-800 m where introduced in China and Australia. In Queensland, Australia, "an abundant weed of roadsides, stream banks and pastures.  It encroaches upon sugarcane plantations and other cultivated areas and is able to invade the understorey of relatively undisturbed woodlands."  (Waterhouse, 2003; p. 483).

Propagation:  "Seeds are readily spread as contaminants of vehicles, building and landscaping materials and garden mulch.  Air-borne seed dispersal also seems to be effective over short distances"  (Waterhouse, 2003; p. 483).

Native range:  South America.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Palau Palau (main island group)	Babeldaob Island	eradicated invasive	Miles, Joel (year unknown) Discovered in seeded area along road. Eradication program carried out in 2007 and apparently successful. Site will be monitored for new seedlings.
Palau Palau (main island group)	Babeldaob Island	eradicated	Space, James C./Lorence, David H./LaRosa, Anne Marie (2009) (p. 9)

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)	Queensland	introduced invasive	Csurhes, S./Edwards, R. (1998) (p. 125)
Australia Australia (continental)	Queensland	introduced invasive	Veldkamp, J. F. (1999) (pp. 119-124)
Australia Australia (continental)	Queensland	introduced invasive	Waterhouse, B. M (2003) (p. 483)
China China	China (People's Republic of)	introduced invasive	Veldkamp, J. F. (1999) (pp. 119-124)
China China	China (People's Republic of)	introduced invasive	Waterhouse, B. M (2003) (p. 483)
China China	Hong Kong	introduced invasive	Wu, Te-lin (2001) (p. 281) As Eupatorium catarium Veldk. In wasteland.
Perú Perú	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Comments:  The distribution of this species in Queensland is now from the islands in Torres Strait to Gympie in SE Queensland (Louise Hucks, pers. com.).

Additional information:
Weed Management Guide from the Government of Australia. (PDF format).

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

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

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

References:

Csurhes, S./Edwards, R. 1998. Potential environmental weeds in Australia: Candidate species for preventative control. Canberra, Australia. Biodiversity Group, Environment Australia. 208 pp.

Miles, Joel. 0. Joel Miles, pers. com.

Space, James C./Lorence, David H./LaRosa, Anne Marie. 2009. Report to the Republic of Palau: 2008 update on Invasive Plant Species. USDA Forest Service, Hilo, Hawai‘i. 227 pp.

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

Veldkamp, J. F. 1999. Eupatorium catarium, a new name for Eupatorium clematideum Griseb., non Sch. Bip. (Compositae), a South American species naturalized and spreading in SE Asia and Queensland, Australia. Garden's Bulletin Singapore 51 (1999): 119-124.

Waterhouse, B. M. 2003. Know your enemy: recent records of potentially serious weeds in northern Australia, Papua New Guinea and Papua (Indonesia). Telopea 10(1):477-485.

Wu, Te-lin. 2001. Check List of Hong Kong Plants. Hong Kong Herbarium and the South China Institute of Botany. Agriculture, Fisheries and Conservation Department Bulletin 1 (revised). 384 pp.