Gamochaeta pensylvanica (Willd.) Cabrera, Asteraceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Other Latin names:  Gnaphalium pensylvanicum Willd.

Common name(s): [more details]

English: Pennsylvania cudweed

Habit:  herb

Description:  "Annual, 10-40 cm tall, usually branched only at base; stems 1-few, erect or ascending.  Basal leaves mostly 0 at flowering, sometimes present and withered.  Lower cauline leaves apetiolate, sparsely tomentose on upper surface, densely tomentose on lower, more or less concolorous to somewhat discolourous, plane, usually obovate and long-cuneate, sometimes oblanceolate, obtuse to acute, mucronate, flat or slightly undulate, (10)-20-40-(60) x 3-8-(12) mm, upper cauline leaves similar but smaller, narrower and broader based, sometimes folded.  Capitula in dense terminal and axillary clusters; clusters usually forming dense terminal spikes at ends of branches and scattered below.  Involucral bracts oblong, obtuse to apiculate, 2.5-3 mm long; stereome green; lamina pale brown, gap and margins clear; outer bracts almost covered by hairs.  Achenes minutely papillate, 0.4-0.5 mm long"  (Webb et al., 1988; pp. 238-239).

Habitat/ecology:  On Raoul Island, "waste places coastal sites, scrubland" (Webb et al., 1988; pp. 238-239).

Propagation:  Seed

Native range:  Temperate and subtropical America.

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	Alford, Mac H. (2012) (p. 3) Vouchers cited: Fagerlund & Mitchell 73 (BISH), Funk s.n. (BISH), Herbst 5295 (BISH), Higashino et al. 10326 (BISH), Hosaka 2080 (BISH), Hosaka 2301 (BISH), Rock 3133 (BISH), Rock 4619 (BISH), Rock 4621 (BISH), Warshauer & McEldowney 2052 (BISH)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Alford, Mac H. (2012) (p. 3) Vouchers cited: Char 78.015 (BISH), Clarke & Corn 366 (BISH), Cuddihy & Char 326 (BISH), Cuddihy & Char 353 (BISH), Cuddihy & Char 355 (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Alford, Mac H. (2012) (pp. 3-4) Vouchers cited: Corn ESP 177 (BISH), Flynn 791 (BISH), Wagner et al. 5157 (BISH)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Alford, Mac H. (2012) (p. 4) Vouchers cited: Degener & Degener 28408 (BISH), Starr 060406-15 (BISH)
State of Hawaii Hawaiian Islands	Ni‘ihau, Lehua Islet	introduced invasive	Wood, K. R./LeGrande, Maya (2006) (p. 20) Voucher cited: Flynn et al. 4852 (BISH, PTBG). Misidentified as Gamochaeta purpurea (L.) Cabrera per Alford (2012).
State of Hawaii Hawaiian Islands	Ni‘ihau, Lehua Islet	introduced invasive	Alford, Mac H. (2012) (p. 4) Voucher cited: Flynn et al. 4852 (BISH, PTBG)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Alford, Mac H. (2012) (p. 4) Vouchers cited: Hosaka 1797 (BISH), Oppenheimer et al H10211 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i, Mokapu Islet	introduced invasive	Alford, Mac H. (2012) (p. 4) Voucher cited: Oppenheimer & Penniman H40918 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Alford, Mac H. (2012) (p. 4) Vouchers cited: Fosberg 29561 (BISH), Hosaka 1847 (BISH)
State of Hawaii Hawaiian Islands	Maui, Molokini Islet	introduced invasive	Alford, Mac H. (2012) (p. 4) Vouchers cited: Hobdy 1239 (BISH), Starr 060405-09 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Alford, Mac H. (2012) (p. 4) Vouchers cited: Degener 18446 (BISH, US), Degener & Topping 11119 (UC, US), Egler 37-55 (BISH), Egler 37-241 (BISH), Fosberg 9475 (BISH), Fosberg 10562 (BISH), Fosberg 12939 (BISH), Herbst & Ishikawa 5269 (BISH), St. John 10406 (BISH), Swarbrick H-17 (BISH), Topping 3071 (UC, US)
Japan (offshore islands) Bonin (Ogasawara) Islands	Bonin (Ogasawara) Islands	introduced	Kato, Hidetoshi (2007) As Gnaphalium pensylvanicum Willd.
New Caledonia New Caledonia	New Caledonia Islands		Swarbrick, John T. (1997) (p. 92)
New Zealand (offshore islands) Kermadec Islands	Raoul Island	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 238) "Waste places, coastal sites, scrubland, local".

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
China China	Hong Kong	introduced invasive	Wu, Te-lin (2001) (p. 282) As Gnaphalium pensylvanicum Willd. In wasteland.
Costa Rica Costa Rica	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Guatemala Guatemala	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Japan Japan	Japan (country)	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 190) As Gnaphalium pensylvanicum Willd.
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Nicaragua Nicaragua	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Additional information:
Additional online information about Gamochaeta pensylvanica is available from the Hawaiian Ecosystems at Risk project (HEAR).

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

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

References:

Alford, Mac H. 2012. New records of Gamochaeta (Asteraceae) in the Hawaiian Archipelago. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2011. Part II: Plants. Bishop Museum Occasional Papers. 113:1-6.

Kato, Hidetoshi. 2007. Herbarium records of Makino Herbarium, Tokyo Metropolitan University. Personal communication.

Mito, Toshikazu/Uesugi, Tetsuro. 2004. Invasive alien species in Japan: the status quo and the new regulation for prevention of their adverse effects. Global Environmental Research 8(2)/2004: 171-191.

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

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.

Wood, K. R./LeGrande, Maya. 2006. An annotated checklist and new island records of flowering plants from Lehua Islet, Ni‘ihau, Hawai‘i. In: Evenhuis, Neal L. and Eldredge, Lucias G., eds. Records of the Hawaii Biological Survey for 2004-2005. Part 1: Articles. Bishop Museum Occasional Papers 87:19-29.

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.