Vachellia aroma (Gillies ex Hooker & Arnott) Seigler & Ebinger var. huarango (Ruiz ex Macbride) Seigler & Ebinger, Phytologia 87:144. 2005.
syn.  Acacia aroma Gillies ex. Hook. & Arn. var. huarango (Ruiz ex J. Macbr.) Ebinger, Seigler and Clarke, Syst. Bot. 25:602. 2000.

Synonymy and types

Basyonym: Acacia huarango Ruiz ex J. Macbr., Publ. Field Mus. Nat. Hist., Bot. Ser. 8:90. 1930. - Acacia aroma Gillies ex. Hook. & Arn. var. huarango (Ruiz ex J. Macbr.) Ebinger, Seigler and Clarke, Syst. Bot. 25:602. 2000. - TYPE: PERU. HUÁNUCO: near Huánuco, low spreading shrub, Ruíz & Pavon s.n. [lectotype, designated by Macbride (1943): F]. NOTE: Macbride (1943), in a list of representative specimens, cited a Ruiz and Pavon specimen, (Huánuco: near Huánuco, low spreading shrub) as the lectotype.  A specimen at F (#845461) with the label Plantae a "Ruiz et Pavon" in vice-regno Peruviano et Chilensi lectae (1778-1788) is probably the specimen mentioned.

Formal description

Low, nearly prostrate shrub usually less than 1.5 mm tall, mostly broader than tall, sometimes to 5 m across. Bark dark gray to dark brown, smooth to shallowly furrowed. Twigs light to dark purplish brown, slightly flexuous, glabrous to densely
puberulent. Short shoots sometimes present above the stipular spines particularly on slow growing branches, to 2 mm long, covered with acuminate stipules and old leaf bases, sometimes developing into long shoots. Leaves alternate, also occasionally clustered on the short shoots, 30-80 mm long. Stipular spines reddish brown, usually becoming light gray with age, symmetrical, terete to angular or rarely flattened, straight, stout, to 10(60)mm x 1.0-2.5 mm near the base, glabrous to puberulent at the base and sometimes throughout. Petiole adaxially grooved, 3-5 mm long, mostly densely puberulent; petiolar gland solitary, located medially to just below the first pinna pair, sessile, circular to elongated, 0.4-0.9 mm long, apex circular, usually depressed to rarely bulbous,mostly densely puberulent. Rachis adaxially grooved, 30-135 mm long, usually lightly puberulent, a sessile, circular gland, 0.2-0.6 mm across, between the upper 1 to 3 pinna pairs. Pinnae (4)12 to 29 pairs per leaf, 10-20 mm long, 2.5-4.0 mm between pinna pairs. Petiolules 0.4-1.1 mm long. Leaflets 20 to 30 pairs per pinna, opposite, 0.4-0.9 mm between leaflets, linear, 1.5-2.5 x 0.5-0.8 mm, glabrous to lightly puberulent beneath, lateral veins not obvious, only one vein from the base, base oblique, margins lightly ciliate, apex broadly acute to obtuse. Inflorescence a densely flowered globose head, 7-10 mm across, solitary (rarely 3) from the nodes. Peduncles 22-40 x 0.4-0.7 mm, usually lightly puberulent. Involucre 4- to 6-lobed, located at the base of the globose head, puberulent, persistent. Floral bracts spatulate, 1.3-1.9 mm long, apex puberulent, deciduous. Flowers sessile, pale yellow; calyx 5-lobed, 1.3-1.8 mm long, the lobes densely puberulent; corolla 5-lobed, 2.0-2.7 mm long, the lobes commonly puberulent; stamen filaments 2.5-4.0 mm long, distinct; ovary glabrous to lightly pubescent, on a stipe to 0.2 mm long. Legumes dark reddish brown, straight to slightly curved, flattened to elliptical in cross section, constricted between the seeds, oblong, 30-150 x 9-15 mm, coriaceous, reticulately striate, usually densely puberulent, eglandular, indehiscent; stipe to 6 mm long; apex acute, narrowing to a beak to 15 mm long. Seeds uniseriate, no pulp, light to dark brown, ovoid to nearly circular, strongly flattened, 5.3-7.3 x 4.0-6.2 mm, smooth; pleurogram nearly oval, 2.5-4.0 mm across. Flowers from October to May.  Chromosome number: Not determined.


Sandy soils in xeric areas, from sea level along the ocean to 3000 m elevation in southwestern Ecuador and adjacent Peru.

Additional info

Most herbarium labels of specimens of Vachellia aroma var. huarango indicate that the plants were low growing, prostrate shrubs less than 1 m tall with a crown diameter of 2-3 m.  From the information on the herbarium sheets, as well as what is mentioned by Svenson (1946) and Madsen (1990), this taxon commonly grows directly on wind-exposed sandy seashores or just behind mangroves.  At higher elevations, it commonly is found along watercourses where specimens are reported to be less than 1 m tall and nearly 5 m across.

Specimens of Vachellia aroma var. huarango are consistently more puberulent that var. aroma, particularly the leaflets, which are lightly puberulent on the lower surface.  In addition, the petiolar glands of var. huarango are nearly circular, smaller (0.4-0.9 mm across), more bulbous and usually densely puberulent. This variety also differs from var. aroma in that the leaflets (mostly less than 2.5 mm long), petioles (3-5 mm long), pinnae (less than 20 mm long), and the number of leaflets per pinna (less than 30) are at the lower size range for V. aroma var. aroma.  Occasional specimens of var. huarango are cyanogenic; of the 30 specimens examined, five gave a weak reaction after 12 hours.

This taxon is easily confused with some specimens of Vachellia macracantha from Peru that has small leaves and leaflets, Macbride (1943) including a specimen of this latter taxon in his list of V. huarango specimens (M. Sawada P-125).  The two taxa are easily separated as V. macracantha is not a low shrub, has a thicker and longer pubescence on the petiole and rachis of the leaves, has petioles that usually exceed 6 mm in length, and stalked petiolar glands.  Variety huarango, in contrast, is a low, spreading shrub, is puberulent on the petiole and rachis of the leaves, has petioles that are less than 6 mm long, and globose, sessile petiolar glands.

Flowering time


Representative specimens








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