Betula ashburneri
Sponsor
Kindly sponsored by the Banks family in memory of Lawrence Banks CBE DL VMH
Credits
Hugh A. McAllister, Kenneth Ashburner, Paul Bartlett & Martin Deasy (2026)
Recommended citation
McAllister, H. A., Ashburner, K., Bartlett, P. & Deasy M. (2026), 'Betula ashburneri' from the website Trees and Shrubs Online (treesandshrubsonline.
Other taxa in genus
- Betula alleghaniensis
- Betula alnoides
- Betula bomiensis
- Betula × caerulea
- Betula calcicola
- Betula celtiberica
- Betula chichibuensis
- Betula chinensis
- Betula cordifolia
- Betula corylifolia
- Betula costata
- Betula cylindrostachya
- Betula davurica
- Betula delavayi
- Betula ermanii
- Betula fargesii
- Betula fruticosa
- Betula glandulosa
- Betula globispica
- Betula gmelinii
- Betula grossa
- Betula gynoterminalis
- Betula humilis
- Betula kweichowensis
- Betula lenta
- Betula luminifera
- Betula lutea
- Betula maximowicziana
- Betula medwediewii
- Betula megrelica
- Betula michauxii
- Betula microphylla
- Betula middendorffii
- Betula nana
- Betula nigra
- Betula occidentalis
- Betula ovalifolia
- Betula papyrifera
- Betula pendula
- Betula populifolia
- Betula potaninii
- Betula pubescens
- Betula pumila
- Betula raddeana
- Betula schmidtii
- Betula skvortsovii
- Betula tianschanica
- Betula utilis
- Betula utilis subsp. albosinensis
- Betula utilis subsp. jacquemontii
- Betula utilis subsp. occidentalis
- Betula utilis subsp. utilis
Editorial Note
This TSO article is an edited digest of the species account in Kenneth Ashburner and Hugh McAllister, The Genus Betula: A Taxonomic Revision of Birches (2013; repr. 2016).
Trees and Shrubs Online, 23 June 2026
In the wild, a multi-stemmed shrub or shrubby tree from 3 m to possibly 10 m, usually with a number of trunks diverging more or less horizontally from soil level. In cultivation a small tree initially with a strong leader. Buds 8–12 × 2.5–4 mm, slender pointed, acute; scales and elongatetriangular stipules persistent; stipules c. 8–10 × 2.5 mm; young shoots reddish green, with silky hairs up to about 0.5 mm lying parallel with the twig axis, and an under layer of very fine, short (0.3 mm), erect, puberulent hairs, densely glandular, with glands initially translucent, becoming translucent reddish and then opaque white as the resin dries. Twigs rough with few, reddish translucent and numerous white glands persisting on 2nd year and older twigs, some hairs also persisting. Leaves glossy, dark green, slightly cordate at base, with short petiole 5–9 mm, fully formed blade up to 5 times petiole, to (35) 42–50 × 28–35 mm, but often smaller, especially in the wild, with 6–10 pairs of closely inserted lateral veins, 2–5.5 mm apart, giving a heavily veined appearance to the leaf, with conspicuous pleating of lamina between the veins; adaxial surface ± glabrous; abaxial surface with small reddish glands and veins silky hairy with axillary hair tufts containing numerous flattened, ribbon-like hairs to 1 mm long by 0.036– 0.050 mm wide. Male catkins c. 14 × 3.5 mm, scales square to circular, ciliate on margins. Fruiting catkins usually single but sometimes in twos or threes with peduncle 5–13 mm, ± erect, to 15(–27) × 8 mm; scales, with mid-lobes protruding and patent or recurved, (2.5) 3.5–4 (5) × 2.5– 4.5 mm, margins ciliate, abaxially hairy, base thick, lobes thin, central lobe oblong, 2–2.5 mm, often acutely pointed and apex very brittle, lateral lobes broadening from base, 1.5–2.0 mm long, with prominent tooth-like projection on adaxial surface between points of insertion of seeds. Seeds 1.25–2 × 2 mm with nutlet c. 1 mm broad and wings c. 0.5–1 mm, narrower than nutlet but very variable; nutlet hairy towards apex, styles c. 0.75 mm. Diploid: 2n=26
Distribution Bhutan Myanmar China southeast Tibet, northwest Yunnan, southwest Sichuan
Habitat On steep mountain slopes, at the upper limit of the forest, sometimes with Betula utilis or with Juniperus sp., and in meadows by snow patches, at 3300–4300 m asl.
In southeast Tibet in October 1997, Hugh McAllister and Keith Rushforth noticed that there seemed to be a significant difference between the lower altitude, single-trunked, large-leaved, typical Betula utilis, and a shrubby birch in the subalpine scrub around and above the tree-line. Even allowing for the few leaves remaining on them at that time of year, these plants looked different in many ways from typical B. utilis, forming multi-stemmed bushes to about 4 m, occasionally to 8–10 m, with dark-grey and peeling bark, smaller leaves with fewer veins, and small, erect fruiting catkins. Seedlings raised from these trees (KR 51616, collected from several localities in the area, proved to be diploid (2n=28), whereas all reported counts for Betula utilis, including some from this area, are tetraploid (2n=56). The trees were assigned to the new species B. ashburneri McAll. & Rushforth, a determination subsequently confirmed by molecular data (Wang et al. 2016). The epithet commemorates the birch expert Kenneth Ashburner (1927–2010).
Further investigation revealed numerous herbarium specimens referrable to the new species, extending its known range further into China and Bhutan; the earliest of which is a 1912 George Forrest collection from Yunnan on the Shweli-Salween divide. As noted in McAllister & Ashburner (2013), these specimens must often have been passed over as a somewhat ‘odd’ form of Betula utilis, but all have the persistent stipules, very warty twigs and small nutlets characteristic of B. ashburneri. Somewhat more surprisingly, in 2009 several mature small trees of Betula ashburneri were found to be growing at Benmore Botanic Garden, raised from seed collected in Bhutan in 1984 by Ian Sinclair and David Long (S&L 5297) (another tree from this collection appears to be a hybrid with B. utilis – the first such recorded). ITS sequence data analysed by Wang et al. (2016) revealed a discrete clade consisting of Betula ashburneri, B. utilis and B. costata.
In the shape and somewhat leathery texture of the leaf, the exfoliating bark, and the usually knobbly male catkins, Betula ashburneri closely resembles tetraploid Betula utilis. The flattened ribbon-like hairs found in the vein axils on the leaf underside have not been detected in any other birch species, and within subgenus Betula persistent stipules are otherwise only found in the dwarf birches (sect. Apterocaryon). Betula ashburneri can be distinguished from B. utilis by its shrubby multi-stemmed habit, more elongated buds, persistent stipules, small glossy leaves with fewer (6–10) pairs of veins, and more-or-less erect fruiting catkins with the central lobes of the scales patent or reflexed, and small nutlets less than 2 × 1 mm (not including the wing). The two species are easily distinguishable as seedlings: in those of B. utilis, successive leaves increase in size, the relatively slow-growing seedlings producing relatively large leaves with at least 8 pairs of veins; by contrast, seedlings of B. ashburneri grow rapidly, producing numerous neat, small, glossy leaves of a very uniform size regularly arranged along the shoots, 42–50 × 28–35 mm, with 6–8 pairs of veins.
Young plants have an attractive upright habit and dark green, neat, glossy foliage. The largest plants in cultivation have now reached 6 m and still have a main trunk, although some have strong basal branches; their bark is a shiny greenish-brown and is peeling.
