Acacia angustissima (Mill.) Britton & Rose, Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Risk assessment from the Government of Queensland, Australia (PDF format).

Other Latin names:  Acacia suffrutescens Rose [= Acacia angustissima var. suffrutescens]; Acacia texensis Torr. & A. Gray [= Acacia angustissima var. texensis]; Acaciella angustissima (Mill.) Britton & Rose [= Acacia angustissima var. angustissima]; Mimosa angustissima Mill.

Common name(s): [more details]

English: prairie acacia, Texas prairie acacia, white-ball acacia

Spanish: carboncillo, chilicap, guajillo blanco, guajito, guapinico, huajillo, timbe, timbre

Habit:  shrub/tree

Description:  "Acacia angustissima is morphologically highly variable. For example, the branchlets can vary from being almost glabrous to being covered with short appressed hairs. Leaf size, venation of the leaflets and flower size are also variable. The following description is of the typical form of the species (i.e. A. angustissima var. angustissima), which is most common in Queensland. It is based largely on the description in Rico Arce and Bachman (2006):  A thornless shrub or small tree usually growing 2-7 m tall with a single short trunk. However, it may very rarely reach up to 12 m in height. Its younger stems are hairless or finely hairy and are usually somewhat striate. The leaves are bipinnate, 10-21 cm long, and usually have 10-17 pairs of pinnae. They are borne on stalks 1.2-3.5 cm long that are sparsely strigulose. The pinnae are 2.5-5 cm long and each bears 20-40 pairs of leaflets. These relatively narrow leaflets are small (2.4-5 mm long and 0.5-2 mm wide) with pointed tips and entire margins. Stipules are inconspicuous (2-2.5 mm long). The whitish flower clusters are globular or ellipsoidal in shape (1-1.5 cm across) and are actually short head-like racemes. They are borne on short peduncles (1-1.5 cm long) and arranged in axillary fascicles, which may sometimes be arranged into larger panicle-like inflorescences. The flat, thin-walled, papery, pods are oblong in shape (3-9 cm long and 6-15 mm wide) with straight or sinuate margins. They are initially green, but turn coffee-brown when ripe. These glabrous pods are acute at the base and apex, with a stipe 7-12 mm long and a beak 2-7 mm long. Each pod contains 8-12 circular seeds 2.5-3.2 mm across. These seeds are arranged transversely in the pod and are clearly separated from each other. Seed production is prolific"  (Csurhes & Navie, 2009, pp. 4-9).

This species is known in Australia as Acaciella angustissima (Mill.) Britton & Rose.  GRIN classifies Acaciella angustissima as a synonym of Acacia angustissima (Mill.) Kuntze var. angustissima. 

For many years these plants in Australia were incorrectly known by the name Acacia boliviana (Csurhes & Navie, 2009, p. 4).

Habitat/ecology:  "A. angustissima prefers tropical climates but can persist in warmer sub-tropical areas. It is best adapted to seasonally dry areas within these climate zones. For example, in eastern Indonesia (which is outside its native range), this species can readily survive an eight-month dry season. Cook et al. (2005) stated that within its native range, annual rainfall varies from 800-3000 mm and mean temperatures range from 25-30° C. However, these authors included a number of closely related species in their assessment. In addition, it is unclear whether their assessment included A. angustissima var. texensis, which inhabits considerably drier areas in Texas with as low as 400 mm rainfall per annum. When considered collectively, it may be reasonable to conclude that the three varieties of this species could inhabit seasonally dry tropical areas with an annual rainfall between 400 and 3000 mm, with perhaps 800-1500 mm being optimal.  A. angustissima grows naturally from near sea level to 2800 m. It can also tolerate cold climates once established, including occasional temperatures below freezing (Cook et al. 2005). A. angustissima prefers free-draining, infertile, acidic soils in its native range (including black and red acid soils). However, it has been cultivated on a wide range of soils, including vertisols of slightly alkaline pH. It responds well to fertiliser when grown on acidic infertile soils (Cook et al. 2005). Field observations of this species in disturbed coastal riparian habitats in south-eastern Queensland (i.e. subtropical climates) and disturbed coastal open dry woodlands in northern Queensland (i.e. tropical climates) tend to support a conclusion that it is able to invade disturbed sites in open forests, dry scrubs (including deciduous scrubs) and certain riparian habitats"  (Csurhes & Navie, 2009, pp. 13-14).

Propagation:  "A.  angustissima usually produces large numbers of seeds. However, at lowland sites (20 m above sea level) in Papua New Guinea, it has been observed to flower but does not produce any seeds, whereas at higher elevation (1650 m) it seeded prolifically. Like most species of Acacia, recruitment tends to occur most readily when competition from other plants is low (Cook et al. 2005). Some plants can also produce new shoots through root suckering. Seeds are hard-coated and can survive for many years when buried in soil (Cook et al. 2005)"  (Csurhes & Navie, 2009, p. 15).

Native range:  "Southern United States, south through Mexico and Central America to Venezuela, Colombia, Peru, Ecuador, Bolivia and northern Argentina"  (Csurhes & Navie, 2009, p. 4).

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	O‘ahu Island		Bishop Museum (U.S.A. Hawaii. Honolulu.) (1986) (voucher ID: BISH 534536) Taxon name on voucher: Acacia angustissima (Mill.) Britton & Rose
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)	introduced	Csurhes, Steve/Navie, Sheldon (2009) (p. 10)
Philippines Philippine Islands	Philippine Islands	introduced	Csurhes, Steve/Navie, Sheldon (2009) (p. 10)

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)	Queensland	introduced cultivated	Csurhes, S./Edwards, R. (1998) (p. 91) As Acacia boliviana
Australia Australia (continental)	Queensland		Batianoff, G. N./Butler, D. W. (2002) As Acacia boliviana
Australia Australia (continental)	Queensland	introduced invasive	Australian Biological Resources Study (2011) As Acacia boliviana Rusby. Vouchers cited: L. Pedley 4955 (BRI, MEL, NSW), D.H.C. Seton s.n. (BRI), I.B. Staples 2185 (BRI)
Australia Australia (continental)	Queensland	introduced invasive cultivated	Csurhes, Steve/Navie, Sheldon (2009) (p. 11) As Acaciella angustissima (Mill.) Britton & Rose
Colombia Colombia	Colombia (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Costa Rica Costa Rica	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011) Also var. angustissima
El Salvador El Salvador	El Salvador (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) Also var. angustissima
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Indonesia Indonesia	Indonesia (Republic of)	introduced invasive	Csurhes, Steve/Navie, Sheldon (2009) (p. 16) As Acacia villosa
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011) Also var. angustissima, var. suffrutescens (Rose) Isely and var. texensis (Torr. & A. Gray) Isely
Nicaragua Nicaragua	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Panama Panama	Panama (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Thailand Thailand	Thailand (Kingdom of)	introduced	Csurhes, Steve/Navie, Sheldon (2009) (p. 10)

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) Also var. suffrutescens (Rose) Isely and var. texensis (Torr. & A. Gray) Isely
United States (continental except west coast) United States (other states)	USA (Florida)	native	U.S. Dept. Agr., Nat. Res. Cons. Serv. (2011)

Additional information:
Fact sheet from the U.S. Department of Agriculture (PDF format).
Fact sheet at the Agroforestree Database.
Fact sheet from Tropical Forages.
Fact sheet from Winrock International.

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

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

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

References:

Australian Biological Resources Study. 2011. Flora of Australia Online. Australian Biological Resources Study, Canberra.

Batianoff, G. N./Butler, D. W. 2002. Assessment of invasive naturalised plants of southeast Queensland. Plant Protection Quarterly 17(1).

Bishop Museum (U.S.A. Hawaii. Honolulu.). 1986. Voucher specimen #BISH534536(J.Lau 2939).

Csurhes, S./Edwards, R. 1998. Potential environmental weeds in Australia: Candidate species for preventative control. Canberra, Australia. Biodiversity Group, Environment Australia. 208 pp.

Csurhes, Steve/Navie, Sheldon. 2009. Weed risk assessment: white ball acacia. Biosecurity Queensland, Queensland Primary Industries and Fisheries, Queensland Government. 23 pp.

ILDIS Co-ordinating Centre. 2011. International Legume Database & Information Service. Online searchable database.

International Center for Research in Agroforestry. 2008. AgroForestryTree database: a tree species reference and selection guide (online resource). World Agroforestry Centre.

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

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.