Acacia mearnsii De Wild., Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

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

Common name(s): [more details]

Chinese: hei jing

English: black wattle, green wattle, late black wattle, tan wattle

French: acacia noir, mimosa argenté, mosa

Maori (Cook Islands): ākasia

Spanish: acacia negra

Habit:  tree

Description:  "Trees, 9-15 m tall. Branchlets angulate, gray-white tomentose. Young leaves golden tomentose, mature leaves gray pubescent; rachis not angulate; pinnae 6-30 pairs, 0.5-5.5 cm, glands at rachis of pinna insertion and elsewhere; leaflets 10-68 pairs, dense, linear, 0.7-6 x 0.4-0.8(-1) mm, margin, abaxial surface, or sometimes both surfaces pubescent. Heads globose, 6-7 mm in diameter, arranged in axillary racemes or terminal panicles; peduncles 7-10 mm; rachis yellow, densely tomentose. Flowers yellowish or white. Legume black, oblong, flat, 5-10 cm x 4-5 mm, slightly constricted between seeds, pubescent. Seeds black, shiny, ovoid"  (Flora of China online).

"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).

"Arbre de 5 à 15 m de hauteur, reconnaissable à ses feuilles bipennées (composées de petites folioles) et ses gousses comprimées au niveau des graines" (Meyer, 2008; p. 35).

Habitat/ecology:  "Riparian habitats, coastal scrub, dry to mesic forests, grassland" (Weber, 2003; p. 16).  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
Chile (offshore islands) Rapa Nui (Easter) Island	Rapa Nui (Easter) Island (Isla de Pasqua)	introduced cultivated	Meyer, Jean-Yves (2008) (pp. 35, 41)
Cook Islands Southern Cook Islands	Rarotonga Island	cultivated	McCormack, Gerald (2013)
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)
Philippines Philippine Islands	Philippine Islands	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)

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 (2013)
Australia Australia (continental)	Australia (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Australian Capital Territory, South Australia, Tasmania, Victoria
China China	China (People's Republic of)	introduced cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)
Indonesia Indonesia	Indonesia (Republic of)	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan Japan	Japan	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan Ryukyu Islands	Ryukyu Islands	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Malaysia Malaysia	Malaysia (country of)	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
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 Island	Taiwan Island	introduced cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013)

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"
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Kueffer, C./Lavergne, C. (2004) (p. 5)
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Baret, Stephane/Rouget, Mathieu/Richardson, David M./Lavergne, Christophe/Egoh, Benis/Dupont, Joel/Strasberg, Dominique (2006) (p. 758)
Seychelles Seychelles Islands	Seychelles Islands	introduced	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

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. (2013)

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, 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)