Desmanthus virgatus (L.) Willd., Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results: 

Reject, score: 9 (Go to the risk assessment (Australia))
High risk, score: 12 (Go to the risk assessment (Pacific))

Other Latin names:  Desmanthus depressus Humb. & Bonpl. ex Willd.; Desmanthus virgatus var. depressus (Humb. & Bonpl. ex Willd.) B. L. Turner; Mimosa virgata L.

Common name(s): [more details]

English: slender mimosa, virgate mimosa, wild tan-tan

French: sensitive de Montravel

Spanish: guajillo, guashillo, huarangillo

Habit:  herb

Description:  "Prostrate, decumbent, or erect herbaceous perennials to 1.5 m tall, much branched from the base.  Taproot 50 cm long, 1-2 cm in diameter, cylindrical, woody, gnarled, bark brown, corky.  Young stems angled, green with red or golden corky ridges, glabrous or sparsely pubescent with white hairs; older stems terete, red or brown, glabrous and shiny.  Stipules persistent, 2.1-9.0 mm long, setiform with a membranous, nerved auricle opposite the petiole, glabrous or pubescent.  Leaves 2.4-8.0 cm long, petiole 1-5 mm long, rachis 7-36 mm long, puberulent; pinnae 2-5 pairs, 11-30 mm long, the lowest pair bearing an orbicular, sessile, crateriform nectary 0.3-1.2 mm long; leaflets 11-23 pairs, nearly sessile, 2.4-7.0 mm long, 0.7-1.6 mm wide, linear-oblong, square-oblique basally, rounded to acute apically, glabrous, finely ciliate along the margin with white hairs, venation obscure except excentric midvein.  Heads 1 per leaf axil, borne on peduncles 0.6-4.0 cm long.  Bract subtending each flower 1.0-2.2 mm long, 0.4-0.8 mm wide, deltate, pale green with red tips, membranous with an opaque midvein, peltate and pedicellate at the center of the head, sessile and often fused into a whorl at the base of the head, strongly 1-nerved, glabrous or minutely ciliolate.  Floral buds obovate, apically rounded.  Heads 0.3-1.0 cm long containing 3-22 sterile, functionally make, and perfect flowers, sterile or male flowers sometimes absent.  Sterile flowers 0-8; calyx 0.6-1.2 mm long, 0.4-1.0 mm wide, 5-lobed, widely obconic, pale green with white margins; petals 1.5-2.0 mm long, 0.25-0.50 mm wide, obovate to oblanceolate, membranous, faintly 1-nerved, white or pale green with white margins; staminodia 10, 1.7-7.5 mm long, the same width as the filaments of the functional stamens to 3 times as wide, white.  Male flowers usually absent, rarely 1, borne above the sterile flowers, lacking an ovary, but with a perianth and androecium like that of the perfect flowers.  Perfect flowers 3-14; calyx 1.5-3.0 mm long, obconic, the tube 1.5-2.6 mm long, 0.6-1.4 mm wide, rimmed with free acute lobes 0.2-1.0 mm long, pale green with white margins, glabrous; petals 2.4-4.0 mm long, 0.4-0.8 mm wide, oblanceolate, green with red or purple tips, glabrous; stamens 10, rarely 5, 3.5-7.0 mm long, anthers eglandular; ovary 1.5-2.4 mm long, linear, glabrous, style 1.9-4.4 mm long, not exserted beyoind the stamens.  Fruiting peduncles 1.0-5.2 cm long bearing 1-11 pods; legumes dehiscent along both sutures; pod 2.2-8.8 cm long, 2.5-4.0 mm wide, linear, straight or slightly falcate, tips acute, rarely attenuate into a short beak to 1 mm, valves chartaceous, convex, glabrous, reddish brown to nearly black at maturity, somewhat wrinkled with raised reticulate veins.  Seeds 9-27 per pod, 2.1-2.9 mm long, 1.4-2.7 mm wide, obliquely inserted, ovate, flattened, red- or golden-brown; pleurogram 0.6-1.1 mm wide, 0.3-1.0 mm deep, U-shaped to lunate, symmetrical" (Luckow, 1993; pp. 134-139).

See Desmanthus pernambucanus for Pacific introductions of Desmanthus.

Habitat/ecology:  "Wild-tantan grows well in deep, well to moderately well-drained silts, clays, loams, and sands with pH's from about 5 to about 8, formed over both igneous and sedimentary rocks. It is seldom seen in shallow, rocky sites. The species is recommended for planting in Australia in areas receiving from 550 to 750 mm of mean annual precipitation (Department of Primary Industries 2002) and grows naturally in Puerto Rico in areas that receive from 750 to about 1600 mm of mean annual precipitation. Wild tantan tolerates seasonal drought without difficulty. The species grows from near sea level up to 300 m in elevation (Skerman and others 1988). Wild-tantan is intolerant of shade. It tolerates severe competition from grass and herbs but disappears when overtopped by trees. The species is usually more or less evenly dispersed in stands of grass and herbs, often at 1 or 2 per square meter. It withstands heavy grazing pressure and recovers well from fire"  (Wildland shrubs of the United States and its territories).  In its native range, "in heavily disturbed areas such as railroad tracks, pastures, roadsides, and even city streets, in coastal thickets and on beaches; 0-1900 m, primarily a lowland species but introduced at higher elevations"  (Luckow, 1993; pp. 134-139).

Arid lowlands and moist uplands in the Galápagos Islands (McMullen, 1999; p. 186).

Propagation:  Seed, dispersed by ruminant animals  (Wildland shrubs of the United States and its territories).

Native range:  "Texas and Florida, U.S.A., eastern and southern Mexico, Central America, the Caribbean, and South America"  (Luckow, 1993; pp. 134-139).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) Galápagos Islands	Galápagos Islands	native	Luckow, Melissa (1993) (p. 139)
State of Hawaii Hawaiian Islands	Hawaiian 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)	Northern Territory	introduced invasive	Australian Biological Resources Study (2013)
Australia Australia (continental)	Queensland	introduced invasive	Australian Biological Resources Study (2013)
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	Luckow, Melissa (1993) (p. 138)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	Luckow, Melissa (1993) (p. 138)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	Luckow, Melissa (1993) (p. 138)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	Luckow, Melissa (1993) (p. 138)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	Luckow, Melissa (1993) (p. 138)
China China	China (People's Republic of)	introduced	ILDIS Co-ordinating Centre (2013)
China China	Hong Kong	introduced cultivated	Wu, Te-lin (2001) (pp. 131-132) Forage.
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 184)
Japan Ryukyu Islands	Ryukyu Islands	introduced	ILDIS Co-ordinating Centre (2013)
Mexico Mexico	Mexico (United Mexican States)	native	Luckow, Melissa (1993) (pp. 136, 138)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 33) Naturalised
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	native	Luckow, Melissa (1993) (p. 139)
South America (Pacific rim) South America (Pacific rim)	Colombia	native	Luckow, Melissa (1993) (p. 139)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	Luckow, Melissa (1993) (p. 139)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	Luckow, Melissa (1993) (p. 139)
Taiwan Taiwan Island	Taiwan Island	introduced	ILDIS Co-ordinating Centre (2013)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
British Indian Ocean Territory Chagos Archipelago	Diego Garcia Island	introduced invasive	Whistler, W. Arthur (1996) (p. 28)
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
French Territory of Mayotte Mayotte Islands	Mayotte Island	introduced invasive	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2013)
Seychelles Seychelles Islands	Agalega Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Stoddart, D. R. (1983) (p. 123)
Seychelles Seychelles Islands	Coetivy Island		Robertson, S. A./Fosberg, F. R. (1983) (p. 150) Voucher cited: Robertson 3127 (K)
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
United States (continental except west coast) United States (other states)	United States (other states)	native	Luckow, Melissa (1993) (p. 135) Texas
United States (continental except west coast) United States (other states)	USA (Florida)	native	Luckow, Melissa (1993) (p. 135)

Comments:  "In a recent monograph of Desmanthus (Luckow, 1993), species of the D. virgatus complex were reinterpreted.  The result is that the species naturalized on many Pacific islands, including the Hawaiian Islands, is now referred to D. pernambucanus" (Wagner & Herbst, 1995).

Control:  If you know of control methods for Desmanthus virgatus, please let us know.