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<big>''[[Alnus acuminata]]'' Kunth</big>
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{{DISPLAYTITLE:''Alnus acuminata'' (PROTA)}}
:Protologue: Humb., Bonpl. & Kunth, Nov. gen. sp. 2: 20 (1817).
:Chromosome number: 2''n'' = 28
== Vernacular names ==
The leaves are palatable for livestock and contain about 16% of crude protein. The bark is rich in tannin.
== Botany Description ==
Deciduous medium-sized tree up to 30(–40) m tall; bole cylindrical, up to 50(–100) cm in diameter; bark surface smooth and grey in young trees, but becoming scaly and ridged with age; crown narrow, dense; young twigs glandular hairy, branchlets with lenticels and conspicuous rounded scars from fallen leaves. Leaves alternate, in 3 rows, simple and entire; stipules ovate to elliptical, 4–8 mm × 1–1.5 mm; petiole (4–)7–23(–35) mm long; blade lanceolate, ovate or elliptical, thinly leathery, (3.5–)5.5–14(–19) cm × (2–)3–9(–10.5) cm, cuneate to obtuse or rounded at base, long-acuminate to rounded at apex, margin toothed, glandular hairy, pinnately veined with 10–15 pairs of lateral veins. Inflorescence a many-flowered catkin; male catkin elongate, pendulous, 5–11 cm long, flowers arranged in groups of 3 in bract axils; female catkin ovate or elliptical, 3–6 mm × 1.5–3 mm, flowers arranged in groups of 2 in bract axils. Flowers unisexual, minute; male flowers 4-merous, with elliptical or obovate perianth segments c. 1.5 mm long, stamens opposite and basally adnate to perianth segments, 2.5–4 mm long; female flowers consisting of a 2-celled ovary with a 2-branched style. Fruit an elliptical to obovate, winged nut 1.5–3 mm long, dark brown, in cone-like, ovoid to ellipsoid infructescence 1–3 cm × 1–1.5 cm. Seedling with epigeal germination; cotyledons leafy, spreading; first 2 leaves opposite.
== Other botanical information ==
Andean alder fixes nitrogen in symbiosis with ''Actinomyces alni'' (synonym: ''Frankia alni''). The flowers are wind pollinated.
''Alnus'' comprises about 40 species, most of them in temperate and subtropical regions of the Northern Hemisphere.
=== ''Alnus nepalensis'' ===''[[Alnus nepalensis]]'' D.Don, native of mainland Asia and Japan, has also been introduced in Africa. It has roughly the same uses as Andean alder and is also being promoted for use in agroforestry systems, but it is better adapted to semi-arid environments.
''Alnus acuminata'' and ''Alnus jorullensis'' Kunth have often been confused. The latter is restricted to Mexico and Guatemala and differs in leaf shape and in its scrubby habit; it is found in drier habitats.
== Ecology ==
Andean alder occurs naturally in the range of 18°N–28°S at altitudes of 1500–3200(–3700) m. It can withstand temperatures below zero for a short time and is adapted to high humidity. Protection from cold dry winds is beneficial. It regenerates well on degraded land and steep mountain slopes.
== Management ==
