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]

Chinese: jia chou cao

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).

Description from the Flora of China online.

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 (Belau ) (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. Report as of 29 May 2013 from Joel Miles: The eradication project is still ongoing. It is still confined to two small sites, but we have not been able to get rid of it.
Palau Palau (Belau ) (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	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Introduced and becoming naturalized in Guangdong.
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.
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan Taiwan Island	Taiwan Island	introduced invasive	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Introduced and becoming naturalized in Taiwan.

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.).

Control:  If you know of control methods for Praxelis clematidea, please let us know.