Alnus orientalis Decne.

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Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus orientalis' from the website Trees and Shrubs Online ( Accessed 2024-05-20.


  • Alnus
  • Subgen. Alnus, Sect. Japonicae

Common Names

  • Oriental Alder


  • Alnus oblongata Kotschy ex Regel
  • Alnus orientalis f. winkleri Callier
  • Betula longifolia Bové ex Spach


Above sea-level.
Heart-shaped (i.e. with two equal lobes at the base).
With evenly triangular teeth at the edge. (Cf. crenate teeth rounded; serrate teeth saw-like.)
(of shoot) Growing out from trunk or major branches.
Channelled or grooved.
Lacking hairs smooth. glabrescent Becoming hairless.
(var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare minor variants more usefully ranked as forms.


Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus orientalis' from the website Trees and Shrubs Online ( Accessed 2024-05-20.

Tree to 25 m, crown upright or spreading. Bark smooth, light to dark gray, smooth or fissured, sometimes fluted. Branchlets green to brown, glabrous to pubescent, terete or angled. Buds ovate to obovate, 3 mm, stalk 3–4 mm. Leaves ovate to elliptic, (2.5–)4–11 × 2–6 cm, apex acuminate or abruptly long-acuminate, obtuse, base cuneate, truncate to rounded, edges undulate, singly to doubly-serrate with minute mucronate teeth, blade flat, coriaceous, matt to glossy, often with whitish resinous blume, adaxially glabrous, adaxially blade glabrous with puberulent veins and hairy domatia, glandular, craspedodromous to semi-craspedodromous, 6–10 pairs of alternate veins, strongly impressed abaxially, adaxially flat. Petiole 2–4 cm, thin, glabrous to pubescent, yellowish green to red. Inflorescences terminal to branch, sometimes subtended by a small leafy bract. Staminate inflorescences in terminal clusters of 2–4(–6), each 25–30 × 4 mm over winter, extending to 40–65 × 8–12 mm at anthesis, sub-erect to pendulous at anthesis, stamens often slightly exposed over winter. Pistillate inflorescences below males, 1–4 in erect cluster, 40–120 × 4–7 mm at anthesis, primary peduncle long, lax, secondary peduncle 2–10 mm, viscid. Fruit ovate, (7–)15–25 × 10–20 mm, viscid, maturing from green to black, bracts woody, with four spreading even rounded lobes, with fifth lobe terminal with mucronate tip. Seed five-sided, 2 mm, lacking membranous wing, or with thickened leathery rim. Flowers January-March, fruits October. (Davis 1984; De Langhe 2018; T. Baxter, pers. obs.).

Distribution  CyprusIranItaly Sicily LebanonSyriaTurkey

Habitat Often abundant in riverine habitats throughout its range, on wet, typically alluvial soils, from sea level to 1500 m asl.

USDA Hardiness Zone 9b

RHS Hardiness Rating H3

Conservation status Least concern (LC)

Alnus orientalis is an attractive species, noted for its splendid male catkins in early spring, albeit less dramatic than those of A. subcordata or A. alnobetula subsp. sinuata. It is an upright and fast-growing tree suited to cultivation in wet areas; potentially of large stature, in cultivation it tends not to reach such dimensions as in favourable habitat in its native range. A tree of the Near East, it grows naturally in Turkey, Cyprus, the southern Caucasus, Syria and Lebanon, where it occurs in a range of riverine habitats on wet soils where it is both an early coloniser and a dominant forest tree. This is a region that was a major refugium during the Pleistocene (Milne & Abbott 2002) for many plants including alders. It is also a complicated area for this genus, with several diploid species whose ranges overlap. It is not known how such a diversity of wind pollinated taxa remain separate. It is likely that refugia contained individual cytotypes that have mixed during interglacial periods. While it has been observed that A. orientalis generally flowers later than A. glutinosa and A. incana, and much later than A. subcordata (T. Baxter pers. obs.), other mechanisms are likely to be involved. As with most alders, it is clear that Oriental Alder is very variable species across its large range; some collections have regular dentate toothing (e.g. TURX 94), some distantly lobulate (WHHD 701), and some shallowly lobed and coarsely dentate (coll. Tasdibi, Turkey) (see images). It is known as a diploid species (Rice et al. 2015), but with probably erroneous reports of tetraploids (H. McAllister pers. obs.).

Hardy only in milder areas of the UK and adjacent maritime Europe, Oriental Alder seems not to tolerate a continental climate and is not regarded as hardy in North America (Tripp 1995) nor in continental Europe, though it could probably be grown more widely on the maritime fringes of western Europe and on the US west coast. It is especially sensitive to drought and late frosts when young, but once established fares much better, although plants at Ness exhibit much epicormic growth due to frost desiccation of twigs (T. Baxter pers. obs.). A specimen grown in the open at the Yorkshire Arboretum, from seed collected by Kenneth Ashburner near Antalya, Turkey, in 1998, was badly damaged by the cold winter of 2010, being cut back to the main trunk. It regenerated but the new growth is very susceptible to spring frost and it has made an ugly specimen; another from the same source, with greater shelter, has made a decent tree of 8.2 m (164 cm girth) in 2020 (The Tree Register 2023). Selection of high-altitude provenances might improve hardiness in cultivation: plants at Ness from c. 1300 m asl in the Troödos mountains of Cyprus appear to be somewhat superior to other origins at Ness, and also have attractive red petioles and fluted trunks. The tallest plants in cultivation in the UK can be found at Tortworth Court, Gloucestershire (22 m in 2015), Tatton Park, Cheshire (20 m in 2015) and Sandling Park, Kent (19.3 m in 2019) (Tree Register 2022).

Alnus orientalis is most similar in appearance to A. subcordata, but differs in its more compact crown, smaller lobulate and more or less glabrous leaves, later flowering time, and smaller inflorescences and cones. A. subcordata is a larger and more vigorous species with hairy young twigs, petioles, and leaf undersurfaces (at least on the veins); leaves typically twice the size of A. orientalis that are never lobed and always single-toothed; cones often held singly, and male catkins appearing over late winter to early spring, distinctly longer than those of A. orientalis. A. orientalis is almost always associated with water, whereas A. subcordata is more drought tolerant and found in a variety of habitats. A. orientalis is readily distinguished from A. cordata as this has smaller, glossy, glabrous, unlobed leaves with cordate bases, larger cones, and flowers much later in spring (T. Baxter pers. obs.).