Ambrosia artemisiifolia L., Asteraceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: annual ragweed, bitterweed, common ragweed, ragweed, Roman wormwood

French: ambroisie annuelle

Spanish: ambrosia de hojas de ajenjo

Habit:  herb

Description:  "Erect, taprooted annual herbs; stems 3-10 dm long, branched at least above, ± hirsute.  Leaves pinnatifid or bipinnatifid, the lobes lanceolate, blades narrowly to broadly ovate or elliptic, 4-10 (-30) cm long, 4-7 (-15) cm wide, upper surface hirsutulous, lower surface strigose and often hirsute on the veins.  Staminate involucre 1.5-2 mm high; pistillate involucre 3-5 mm high in fruit with a single series of short, sharp, erect spines near or above the middle."  (Wagner et al., 1999; p. 256).

Known to hybridize with Ambrosia psilostachya.

Habitat/ecology:  In Hawai‘i, "naturalized in low elevation, dry, disturbed habitats, especially along roadsides and in pastures, 0-900m" (Wagner et al., 1999; p. 256).

Propagation:  Seed

Native range:  United States and southern Canada (Wagner et al., 1999; p. 256).

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	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced	Wester, Lyndon (1992) (p. 127)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 256)

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)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)
Canada Canada	Canada (country)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Chile (continental) Chile	Chile (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)
China China	China (People's Republic of)	introduced invasive	Li-ying, Li/Ren, Wang/Waterhouse, D. F. (1997) (pp. 172, 178)
China China	Hong Kong	introduced invasive	Wu, Te-lin (2001) (p. 274) In wasteland.
Colombia Colombia	Colombia (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)
Guatemala Guatemala	Guatemala (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)
Japan Japan	Japan (country)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)
Taiwan Taiwan	Taiwan Island	introduced invasive	Ching-I Peng, ed. (2011) "A widely naturalized weed along freeways, open construction sites and waste places in lowlands".

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 21)

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)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Additional information:
Draft European and Mediterranean Plant Protection Organization datasheet.
Information from the Global Invasive Species Database.
Fact sheet from the Government of Australia (PDF format).

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

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

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

References:

Ching-I Peng, ed. 2011. Digital flora of Taiwan (online resource).

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.

Li-ying, Li/Ren, Wang/Waterhouse, D. F. 1997. The distribution and importance of arthropod pests and weeds of agriculture and forestry plantations in southern China. ACIAR, Canberra, Australia. 185 pp.

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

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Wester, Lyndon. 1992. Origin and distribution of adventive flowering plants in Hawai‘i. In: Stone, Charles P.; Smith, Clifford W. and Tunison, J. Timothy. Alien plant invasions in native ecosystems of Hawaii: Management and Research. University of Hawaii, Cooperative National Park Research Studies Unit, Honolulu. University of Hawaii Press. .

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.