Vachellia caven - spines

Vachellia caven - habit


Vachellia caven (Molina) Seigler & Ebinger, Phytologia 87:  148.  2005.
syn.  Acacia caven (Molina) Molina, Sag. Stor. Nat. Chili, 2nd ed. 163.  299.  1810.

Synonymy and types

Basionym:  Mimosa caven Molina, Sag. stor. nat. Chili, ed 1, 174. 1782.  Mimosa cavenia Molina, Eassai hist. nat. Chili, 338.  1789.  Acacia caven (Molina) Molina, Sag. stor. nat. Chili, 2nd. ed., 163, 299. 1810.  Acacia cavenia (Molina) Hook. & Arn., Misc. Bot. 3: 206.  1833.  Acacia farnesiana (L.) Willd.  var. cavenia (Molina) Kuntze, Revis. gen. pl.  3(2): 47.  1898.  Acacia farnesiana (L.) Willd. var. cavenia (Hook. & Arn.) Arechav., Anales Mus. Nac. Montevideo  1: 436.  1901.  Vachellia farnesiana (L.) Wight & Arn. f. cavenia (Molina) Speg., Bol. Acad. Nac. Ci. Córdoba 26: 297.  1923.  Acacia farnesiana (L.) Willd. f. cavenia (Hook. & Arn.) E. C. Clos., Bol. Minist. Agric. Nac. (Argentina) 28: 455.  1930. - TYPE:  CHILE.  Raneagna, Oct 1828, C. G. Bertero s.n. [lectotype, designated by Aronson (1992):  SG0].  NOTE:  We interpret the specific epithet cavenia to be a misspelling.

Acacia adenopa Hook. & Arn., Bot. Misc.  3: 206.  1833. - TYPE:  Islands of the Uruguay, J. Tweedie s.n. (holotype:  K).

Acacia aromatica Poepp., Mart., Fl. Bras.  15: 395.  1879. - TYPE:  CHILE.  Valparaiso, E. Poeppig 177 [lectotype, designated by Ebinger et al. (2000):  W].

Acacia farnesiana (L.) Willd. var. brachicarpa Kuntze, Revis. gen. pl.  1: 156.  1891. - TYPE:  none cited, from Argentina, Córdoba.

Acacia farnesiana (L.) Willd. var.  heterocarpa Kuntze, Revis. gen. pl.  3(2): 47.  1898. - TYPE:  ARGENTINA.  CÓRDOBA:  Dec 1891, O. Kuntze s.n. [lectotype, designated by Ebinger et al. (2000):  MO].

Acacia caven (Molina) Molina var. dehiscens Burkart ex Ciald., Darwiniana  25: 76.  1984. - TYPE:  ARGENTINA.  CÓRDOBA:  Ascochinga, 22 Sep 1936, E. G. Nicora 962 (holotype:  SI).

Acacia caven (Molina) Molina var. microcarpa (Speg.) Burkart ex Ciald., Darwiniana  25: 77.  1984. - Vachellia farnesiana (L.) Wight & Arn. f. microcarpa Speg., Bol. Acad. Nac. Ci. Córdoba  26: 301.  1924. - TYPE:  ARGENTINA.  FORMOSA:  Depto. Patino, Fortin Soledad, A. Krapovickas 1283 [lectotype, designated by Cialdella (1984):  SI; isotype:  LIL].

Acacia caven (Molina) Molina var. stenocarpa (Speg.) Burkart ex Ciald., Darwiniana  25: 78.  1984.  Vachellia farnesiana (L.) Wight & Arn. f. stenocarpa Speg., Bol. Acad. Nac. Ci. Córdoba 26:301. 1924. -  TYPE:  ARGENTINA.  MISIONES:  Depto. Candelaria, Santa Ana, A. Burkart 14734 [lectotype, designated by Cialdella (1984):  SI].

Acacia caven (Molina) Molina var. sphaerocarpa Burkart ex Aronson, Ann. Missouri Bot. Gard. 79: 964.  1992. - TYPE:  ARGENTINA.  CORRIENTES:  ca. 27° 27'S, 58° 46'W, 60 m. "alrededores de la ciudad de Corrientes, antiguo camino a Matadero, 50 m de la ruta, 17 Feb 1989, S. G.Tressens & A. Radovancich 3539  (holotype:  K; isotype:  CTES).

Acacia caven (Molina) Molina var. macrocarpa Aronson, Ann. Missouri Bot. Gard.  79: 965.  1992. - TYPE:  ARGENTINA.  SALTA:  Salta, Chicoana, El Carril, 19 Oct 1948, A. Burkart 17577 (holotype:  SI).

Vachellia farnesiana (L.) Wight & Arn. f. brachypoda Speg., Bol. Acad. Nac. Ci. Córdoba  26: 301.  1924. - TYPE:  not cited, from Argentina, Buenos Aires Prov., San Fernanda, Gualeguaychu, Ibicuy y chaco santefecino.

Formal description

Shrub or small tree to 7 (10) m tall.  Bark dark gray to brown, furrowed.  Twigs dark purplish brown to black, slightly flexuous, glabrous to densely puberulent.  Short shoots commonly present above the stipular spines, to 15 mm long, covered with acuminate stipules and old leaf bases.  Leaves alternate, also commonly clustered on spur branches, 25-55 mm long.  Stipular spines dark reddish brown, becoming light gray with age, symmetrical, terete, straight, stout, to 30(50) x 3.0 mm near the base, puberulent at the base and sometimes throughout.  Petiole adaxially grooved, 5-11 mm long, puberulent; petiolar gland solitary, located on the upper half of the petiole, sessile, elongated, 0.5-1.4 mm long, (sometimes circular on short shoot leaves), apex depressed, glabrousRachis adaxially grooved, 5-45 mm long, usually densely puberulent, a sessile, circular gland, 0.3-0.4 mm across present between the upper 1 to 3 pinna pairs.  Pinnae 3 to 10 pairs per leaf, 12-22 mm long, 1.5-5.5 mm between pinna pairs.  Petiolules 0.4-1.4 mm long.  Leaflets 11 to 26 pairs per pinna, opposite, 0.5-1.4 mm between leaflets, linear, 1.0-4.0 x 0.4-0.9 mm, mostly glabrous, lateral veins not obvious, only one vein from the base, margins sometimes sparsely ciliate, apex acuteInflorescence a densely flowered globose head 7-10 mm across, solitary or in clusters of 2 to 10 on the short shoots.  Peduncles 6-11(16) x 0.4-0.6 mm, lightly to densely puberulent.  Involucre 4- to 5- lobed, located at the base of the globose head, puberulent, persistent.  Floral bracts spatulate, 0.7-1.1 mm long, puberulent, deciduous.  Flowers sessile, pale yellow; calyx 5-lobed, 1.0-1.5 mm long, the lobes usually puberulent; corolla 5-lobed, 1.8-2.5 mm long, the lobes usually puberulent; stamen filaments 3.0-4.5 mm long; distinct ovary glabrous, on a stipe to 0.1 mm long.  Legumes dark brown to black, straight, nearly circular in cross section, not  constricted between the seeds, oblong, 20-95 x 13-25 mm wide, coriaceous, lightly reticulately striate, glabrous, eglandular, indehiscent; stipe absent to 4 mm long; apex narrowing to a short beak to 10 mm long.  Seeds biseriate to irregularly arranged in a white to reddish pulpy material, light to dark reddish brown, ovoid to ellipsoid, slightly flattened, 4.3-7.2 x 3.3-5.4 mm, smooth; pleurogram U-shaped, 2.5-4.0 mm across.  Flowers in June to November. Chromosome number:  2n = 26 (Castronovo 1945).


Shrubby vegetation of pastures, successional fields, stream banks and other disturbed sites, rocky slopes, thorn -scrub grasslands, open savannas, and inundated plains from near sea level to 3200 m in northern Argentina, southern Bolivia, Paraguay, Uruguay, southeastern Brazil, and the Mediterranean-type climate zone of Chile (Aronson and Ovalle 1989).

Additional info

Vachellia caven is an extremely wide-ranging species that probably originated in the warm temperate to subtropical biogeographical region known as the Gran Chaco of southern South America (Aronson and Ovalle 1989).  This region extends through much of north central Argentina, adjacent portions of Bolivia, a small part of the Matto Grosso of Brazil, and nearly half of Paraguay.  Vachellia caven also is common in the Central Valley of Chile in a number of natural ecosystems of both the semi-arid and subhumid portions of the Mediterranean-type climate of that country.  Ovalle et al. (1990) suggest that it is probably an invasive species that has become common by radical changes to the landscape brought about by European colonization.

This species is characterized by a great deal of ecological versatility and morphological variation. It occurs from near sea level to more than 3200 m in mountainous terrain, probably being limited by freezing temperatures. Vachellia caven is also known from near desert conditions in Chile to seasonally inundated savannas in Argentina and Paraguay.  Extensive variation in plant height is also reported, mostly due to land use, moisture, fire and past cutting.  Rarely, ants inhabit the thorns of this species.  One specimen (Mereles 1130 from Paraguay) had a small hole near the tip of the thorn.  The stipular thorns on this specimen were more than 70 mm long and 10 mm wide at the base.

This species is similar to Vachellia farnesiana and V. tortuosa in that it commonly produces short shoots from which clusters of relatively small leaves develop.  These leaves are usually much smaller than the leaves that develop on rapidly growing shoots, have smaller and fewer pinnae, smaller leaflets, smaller petiolar glands, and a rachis that commonly lacks a groove on the upper surface.  Although rarely are there more than 10 pinna pairs to a leaf, even on rapidly growing shoots, occasional individuals have a few more. Even on these specimens many of the leaves have fewer than 10 pinna pairs, and the leaves developing on the short shoot commonly have fewer than 6 pinna pairs.

Fruit size and shape is highly variable, with Spegazzini (1924), and more recently, Aronson (1992), describing six varieties of Vachellia caven based upon pod morphology (dehiscence, shape, size, mesocarp color and structure, and sutural ridges). These include var. caven with elongated, dark brown pod 5-8 cm long, with one sutural ridge; var. macrocarpa Aronson with elongated, reddish purple pods more than 8 cm long, with three distinct sutural ridges; var. stenocarpa (Speggazini) Burkart ex Cialdella with light brown, fusiform pods 3-4 cm long; var. microcarpa (Speggazini) Burkart ex Cialdella with subglobose pods 2-3 cm long by 1-1.5 cm wide, and a reddish mesocarp; var. sphaerocarpa Burkart ex Aronson with subglobose pods 2.l-6.5 cm long by 1.6-4.8 cm wide, and a white mesocarp; and var. dehiscens Burkart ex Cialdella with dehiscent pods.  No other morphological traits are consistently associated with the pod characteristics.
Baranelli et al. (1995) noted that the fruit are not always constant on a single tree.  Also, the geographic separation of these varieties, at the present, appears tenuous. It is the opinion of the present authors that these variations in pod morphology are too variable to serve as a basis for distinguishing varieties.

Molina (1810) originally described this taxon from specimens found in central Chile, and considered it to be closely related to V. farnesiana.  These two species are superficially similar, and, as a result, some subsequent authors have merged the two taxa (Hassler 1909, Spegazzini 1924).  The two taxa are distinct, and, except for possibly in southeastern Brazil, are not sympatric.  Both species have inflated pods, short shoots with numerous small leaves, and similar flowers and inflorescences. In V. farnesiana the petiole has a small, circular gland that is raised above the petiolar groove, leaves with 1-6 pinna pairs, and the leaflets with obvious lateral veins.  Vachellia caven, in contrast, has larger, elongated petiolar glands that are sessile in the petiolar groove, many of the leaves have more than 6 pinna pairs, and the leaflets lack obvious lateral veins.

Aronson and Nash (1989) found that a few herbarium specimens (5 of 40) released cyanide, while Aronson (1990) observed a slight cyanogenic reaction with some seedlings and mature trees of this taxon.  During the present study of the 158 herbarium specimens examined for hydrogen cyanide, nine were cyanogenic, five strongly so.

Flowering time


Representative specimens


Buenos Aires:


Dep. Paclín, Cuesta de La Vina:




Entre Ríos:



La Rioja:



San Luis:

Santiago del Estero:


Isla Martín García:



La Paz:

Santa Cruz:



Mato Grosso:

Río Grande do Sul:
















Presidente Hayes:

State not known:


San José: