Vachellia ruddiae (D. H. Janzen) Seigler & Ebinger, Phytologia 87:  166.  2005.
syn. Acacia ruddiae D. H. Janzen, Smithsonian Contr. Bot. 13:  34.  1974.

Synonymy and types

Basionym:  Acacia ruddiae D. H. Janzen, Smithsonian Contr. Bot.  13: 34.  1974. - TYPE:  COSTA RICA.  LIMÓN:  ferry landing, Moin River, Moin, 13 Feb 1965, D. H. Janzen 828 (holotype:  US; isotypes: CAS, F, GH, MEXU, MICH, MO, NY, UC).

Formal description

Tree to 30 m tall.  Bark not seen.  Twigs dark brown to dark reddish brown, not flexuous, glabrous to puberulent.  Short shoots absent.  Leaves alternate, 130-400 mm long.  Stipular spines dark reddish brown to black, symmetrical, terete, straight, stout and inflated, 40-95 x 4-9 mm near the base, glabrous to lightly puberulent, many spines not enlarged, these usually less than 8 mm long and to 0.4 mm wide.  Petiole adaxially grooved, 6-25 mm long, densely puberulent; petiolar glands commonly absent, rarely 1 or 2 scattered along the petiole, sessile, cylindrical to urn-shaped, narrowing toward the base, apex circular, 0.4-0.9 mm across, glabrous and striateRachis adaxially grooved, 110-380 mm long, densely puberulent, an urn-shaped gland located between each pinna pair.  Pinnae 17 to 40 pairs per leaf, 30-55 mm long, 5-13 mm between pinna pairs.  Petiolules 0.5-1.2 mm long.  Leaflets 25 to 75 pairs per pinna, opposite, 0.4-1.1 mm between leaflets, linear, 3.5-6.5 x 0.6-1.1 mm, glabrous, lateral veins not obvious, only one vein from the base, base oblique, margins ciliate, apex acute; beltian bodies absent.  Inflorescence a densely flowered globose head, 6-7 mm across, in clusters of 1 to 8 in the axil of normal leaves.  Peduncles 8-11 x 0.5-0.7 mm, densely puberulent.  Involucre 5-lobed, located near the middle of the peduncle, puberulent, persistent.  Floral bracts peltate, 0.5-0.8 mm long, apex circular and ciliate, deciduous.  Flowers sessile, pale yellow; calyx 5-lobed, 0.7-1.0 mm long, glabrous; corolla 5-lobed, 1.3-1.6 mm long, glabrous; stamen filaments 2.1-2.9 mm long, distinct; ovary glabrous, sessile.  Legumes not seen.  Seeds not seen. Flowers in July. Chromosome number:  Not determined.


Very wet rainforest, particularly in primary succession along rivers, at the edge of swamps, and on landslide scars in the Caribbean lowland, from the Puerto Barrios area of Guatemala to northern Panama (Ebinger and Seigler 1995).

Additional info

Vachellia ruddiae is probably most closely related to V. cookii and V. janzenii, which it resembles in having small globose inflorescences, large leaves with numerous small leaflets, and rachis glands between each pinna pair.  However, both V. cookii and V. janzenii have asymmetrical stipular spines that usually curve around the stem, whereas V. ruddiae has symmetrical spines.  Also, the rachis glands of V. ruddiae are urn-shaped, narrowing slightly toward the base, whereas in V. cookii and V. janzenii they are elongated to volcano-shaped.

Though Vachellia ruddiae has a relatively extensive geographic range in the Caribbean lowlands from Guatemala to Panama, it rarely has been collected.  Calvert and Calvert (1917) mention a bull-horn acacia in Costa Rica that had swollen thorns and urn-shaped rachis glands, but lacked Beltian bodies and obligate acacia-ants.  Although referring to this species as Acacia campechiana Miller (syn. V. campechiana, A. cochliacantha), there is little doubt that the taxon discussed is V. ruddiae.

This wet forest species is only marginally an ant-acacia.  Janzen (1974) found that relatively few of the stipular spines were swollen, none were occupied by obligate acacia-ants, and Beltian bodies were not formed on the leaflets.  During the present study, no indication of Beltian bodies was found on developing leaflets and all of the mature leaflets examined lacked the scar left by these bodies.  However, a characteristic entrance hole made by ants was observed on two specimens (Correa A. et al. 3581 and Janzen 819). These probably represent chance encounters, as none of the other spines on the specimens had entrance holes.

Of the specimens of Vachellia ruddiae examined, none tested positive for HCN production.  Seigler and Ebinger (1987) obtained similar results, finding one individual that was weakly cyanogenic while the rest tested negative.

Flowering time


Representative specimens





San José:








Bocas del Toro: