Ageratum houstonianum Mill., Asteraceae

Click on an image for links to BIGGER PICTURES

Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Ageratum mexicanum Sims

Common name(s): [more details]

Chinese: xiong er cao

English: Mexican ageratum, ageratum, blue billygoat weed, bluemink, flossflower, goatweed

Fijian: botebotekoro, mbotembotekoro, sogovanua, songovanua

French: ageratum du Mexique

Hawaiian: maile hohono, maile honohono, maile kula

Spanish: agérato

Habit:  herb

Description:  "Annual, usually erect and often much branched, the stems leafy throughout, pilose or villous with spreading hairs; leaves opposite, on rather long, slender petioles, very thin, broadly deltoid-ovate, mostly 4-8 cm long, obtuse or acute, generally shallowing cordate at the base, coarsely crenate, thinly villous-hirsute, not punctate beneath; corymbs terminal on the branches, often compound, glandular-hirtellous and villous with several-celled hairs; heads numerous lavender or pale blue, 8 mm broad, about 75-flowered; phyllaries narrowly lanceolate or linear, entire, herbaceous, long-attenuate, ciliolate, usually purplish toward the apex, 2-costate, glandular-puberulent; achenes black, lustrous, commonly hispidulous, at least on the angles, 1.2 mm long; pappus scales 5, lanceolate, fimbriate-margined, long-setiferous, about equaling the corolla" (Nash & Williams, 1976; p. 39).

"Coarse herb, semiprostrate toward base and with ascending branches 0.3-1 m high...  The corolla lobes and styles are pale blue to purple."  (Smith, 1991; pp. 296-297).

Description from the Flora of China online.
Description from the Flora of North America online.

Habitat/ecology:  In Hawai‘i, "naturalized in a wide variety of disturbed habitats, especially along trails and roadsides, 40-1,300 m" (Wagner et al., 1999; p. 256). In Fiji, "sometimes cultivated and also naturalized at elevations from near sea level to 1,127 m in open places, along roadsides, on river banks, and on cleared upland slopes and crests"  (Smith, 1991; pp. 296-297). In New Guinea, "established in a few localities above 1000 m" (Henty & Pritchard, 1975; p 63).

Propagation:  Seed

Native range:  Mexico, central America and the West Indies (Wagner et al., 1999; p. 256); cultivated and naturalized (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Fiji Fiji Islands	Viti Levu Island	introduced invasive cultivated	Smith, Albert C. (1991) (pp. 296-297) Vouchers cited: Parks 20625, Parks 20626, Smith 5019, DA 2729, DA 8530, DA 11114, DA 10371, Vaughan 3246, DA 11327, DA 11123, DA 12117
French Polynesia Marquesas Islands	Nuku Hiva (Nukahiva) Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Adventice
French Polynesia Society Islands	Huahine Island	introduced invasive cultivated	Welsh, S. L. (1998) (p. 69) Voucher cited: Fosberg 63009
French Polynesia Society Islands	Tahiti Island	introduced invasive cultivated	Welsh, S. L. (1998) (p. 69) Voucher cited: Fosberg 64999
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Vouchers cited: J. Florence 3287 (PAP), J. Florence 6626 (PAP) Adventice
French Polynesia Austral (Tubuai) Islands	Raivavae (Raevavae) Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Adventice
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Oppenheimer, Hank L./Bartlett, R. T. (2000) (p. 2) East Maui. Voucher cited: Oppenheimr H69910 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256) Voucher cited: Garber 95 (BISH)
Japan (offshore islands) Ogasawara (Bonin) Islands	Bonin (Ogasawara) Islands	introduced	Kato, Hidetoshi (2007)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced	MacKee, H. S. (1994) (p. 31) Vouchers cited: MacKee 31210, Fallen 176 (NOU), Fukuoka et al. C-90, H. Brinon 267 (NOU), Toutain 3570 (NOU)
New Zealand (offshore islands) Kermadec Islands	Raoul Island	introduced invasive	Sykes, W. R. (1977) (p. 85)
New Zealand (offshore islands) Kermadec Islands	Raoul Island	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 206) "Common on Raoul and nearby islets. Waste places and disturbed areas".
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	invasive	Henty, E. E./Pritchard, G. H. (1975) (p. 63) Established in a few localities above 1000 m.

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)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Australia Australia (continental)	Queensland	introduced invasive	Queensland Herbarium (2002) (p. 1)
Central America Central America (Pacific rim)	Guatemala (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	introduced invasive cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Jiangsu, Nanhai Zhudao, Shandong, Sichuan, Yunnan, Zhejiang "Grasslands, roadsides, slopes in valleys; 100-1500 m. Cultivated and naturalized".
China China	Hong Kong	introduced invasive	Wu, Te-lin (2001) (p. 273) On farmland or in wasteland.
Indonesia Indonesia	Indonesia (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 10)
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 189)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Chiapas, Hidalgo, Jalisco, Morelos, Nayarit, Oaxaca, Veracruz
New Zealand New Zealand	New Zealand (country)	introduced cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 206)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Taiwan Taiwan Island	Taiwan Island	introduced invasive	Ching-I Peng, ed. (2013) "A common weed from low to middle elevations throughout Taiwan".
Thailand Thailand	Thailand (Kingdom of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
United States (continental except west coast) United States (other states)	USA (Florida)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized

Control:  If you know of control methods for Ageratum houstonianum, please let us know.