Acacia mearnsii De Wild., Fabaceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  no

Risk assessment results:  High risk, score: 15 (Go to the risk assessment)

Common name(s): [more details]

English: black wattle, tan wattle

French: acacia noir, mosa

Maori (Cook Islands): ākasia

Spanish: acacia negra

Habit:  tree

Description:  "Unarmed, evergreen tree 5-10 (-15) m high; branchlets shallowly ridged; all parts finely hairy; growth tips golden-hairy.  Leaves:  Dark olive-green, finely hairy, bipinnate; leaflets short (1.5-4 mm) and crowded; raised glands occur at and between the junctions of pinnae pairs.  Flowers:  Pale yellow or cream, globular flowerheads in large, fragrant sprays.  Fruits:  Dark brown pods, finely hairy, usually markedly constricted"  (Henderson, 1995; p. 55).

Habitat/ecology:  This noxious, evergreen tree often reaches 20 m in height. Apart from producing copious numbers of seeds, it generates numerous suckers resulting in monotypic thickets.  It grows in disturbed, mesic habitats between 600-1,700 m.  In Hawai‘i, "naturalized in pastures and dry to mesic forest, 245-1,220 m" (Wagner et al., 1999; pp. 642-643).

Propagation:  Prolific seeder, closes in pastures and displaces natives in natural areas"  (Mootka et al., 2003).  The species resprouts by basal shoots following fire, thereby generally intensifying the infestation.

Native range:  Australia.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Cook Islands Southern Cook Islands	Rarotonga Island	cultivated	McCormack, Gerald (2007)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 642-643)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive cultivated	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 35) Voucher cited: Starr, Starr, Higashino & Price 041227-2 (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 642-643)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 642-643)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 642-643)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Hughes, Guy D'Oyly (1995) (p. 5) Voucher cited: Hughes 51 (US) Rapidly spreading, forming monotypic stands, and displacing native species, below 850 m elevation.
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 642-643)

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)	New South Wales	native	Australian Biological Resources Study (2007)
China China	China (People's Republic of)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Japan Ryukyu Islands	Ryukyu Islands	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2007)
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 707) "Waste places, scrubland, pasture, riverbanks".
Taiwan Taiwan	Taiwan Island	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2007)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	MacDonald, I. A. W./Thebaud, C./Strahm, W. A./Strasberg, D. (1991) (pp. 51-61)
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Lavergne, Christophe (2006) "Très envahissant"
Seychelles Seychelles Islands	Seychelles Islands	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2007)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
South Africa South Africa	South Africa (Republic of)	introduced	Henderson, Lesley (1995)
United States (continental except west coast) United States (other states)	United States (other states)	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2007)

Comments:  On the State of Hawaii noxious weed list. A noxious weed species in South Africa and La Réunion.

Control: 

Chemical: Saplings sensitive to foliar applications of triclopyr. Dicamba, glyphosate and picloram applied cut-surface effective (45), triclopyr probably effective, although applications to drilled holes in larger trees probably necessary. Cut-surface (notching) applications of picloram provided complete control, glyphosate and dicamba caused 80% control, and 2,4-D was inadequate at Kala'e, Molokai. Alton Arakaki (Univ. Hawaii) and Ed Misaki of the Nature Conservancy (TNC) confirmed the efficacy of picloram but got much better results with glyphosate and dicamba, each resulting in over 90% control at Kamakou Preserve. Basal bark and stump bark treatments with 2,4-D or triclopyr effective. Pat Bily (TNC) reported that basal bark applications with triclopyr ester at 20% in oil was effective, as was cut stump application of triclopyr amine at 50% in water.  Hawaii Volcanoes National Park (HAVO) staff got good control with triclopyr amine at 10% in water applied to cut stumps (Chris Zimmer, HAVO).  Anecdotes indicate that wattle is sensitive to basal bark treatment with diesel alone and to girdling (stripping the bark)."  (Motooka et al., 2003)

Additional information:  Information from the book "Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide" (Motooka et al., 2003). (PDF format).
Information from the Purdue University NewCROP web site.
Fact sheet from "Common forest trees of Hawaii" (PDF format).
Information from the World Agroforestry Centre's AgroForestryTree Database.

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

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

References:

Australian Biological Resources Study. 2007. Flora of Australia Online. Australian Biological Resources Study, Canberra.

Cronk, Q. C. B./Fuller, J. L. 2001. Plant invaders. Earthscan Publications, Ltd., London. 241 pp.

Henderson, Lesley. 1995. Plant invaders of Southern Africa. Plant Protection Research Institute Handbook No. 5, Agriculture Research Council, ARC/LNR, Pretoria, South Africa. 177 pp.

Hughes, Guy D'Oyly. 1995. New Hawaiian plant records II. In: Evenhuis, Neal L. and Miller, Scott, E., eds. Records of the Hawaii Biological Survey for 1994. Part 2: Notes. Bishop Museum Occasional Papers. 42:1-10.

Lavergne, Christophe. 2006. List des especes exotiques envahissantes a La Reunion. Unpublished manuscript (Excel file). .

Little, Elbert L./Skolmen, Roger G. 1989. Common forest trees of Hawaii (native and introduced). USDA Agriculture Handbook 679. Washington, D.C. 377 pp. + plates.

MacDonald, I. A. W./Thebaud, C./Strahm, W. A./Strasberg, D. 1991. Effects of alien plant invasions on native vegetation remnants on La Reunion (Mascarenes Islands, Indian Ocean). Environmental Conservation 18 (1):51-61.

McCormack, Gerald. 2007. Cook Islands biodiversity and natural heritage. On-line database.

Motooka, Philip/Castro, Luisa/Nelson, Duane/ Nagai, Guy/Ching, Lincoln. 2003. Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. 184 pp.

Motooka, Philip/Ching, Lincoln/Nagai, Guy. 2002. Herbicidal Weed Control Methods for Pasture and Natural Areas of Hawaii. Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i. CTAHR free publication WC-8.

Smith, Clifford W. 1985. Impact of Alien Plants on Hawai‘i's Native Biota. In: Stone, Charles P. and Scott, J. Michael, eds. Hawai‘i's terrestrial ecosystems: preservation and Management. Cooperative National Park Resources Studies Unit, University of Hawaii, Manoa.

Starr, Forest/Starr, Kim/Loope, Lloyd L. 2006. New plant records from the Hawaiian Archipelago. 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 87:31-43.

U.S. Dept. Agr., Agr. Res. Serv. 2007. 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).

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.