Alnus rohlenae
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Credits
Tim Baxter & Hugh A. McAllister (2024)
Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus rohlenae' from the website Trees and Shrubs Online (treesandshrubsonline.
Genus
- Alnus
- Subgen. Alnus, Sect. Glutinosae
Other taxa in genus
- Alnus acuminata
- Alnus alnobetula
- Alnus betulifolia
- Alnus cordata
- Alnus cremastogyne
- Alnus djavanshirii
- Alnus dolichocarpa
- Alnus × elliptica
- Alnus × fallacina
- Alnus fauriei
- Alnus ferdinandi-coburgii
- Alnus firma
- Alnus formosana
- Alnus glutinosa
- Alnus hirsuta
- Alnus incana
- Alnus inokumae
- Alnus japonica
- Alnus jorullensis
- Alnus lanata
- Alnus lusitanica
- Alnus maritima
- Alnus matsumurae
- Alnus × mayrii
- Alnus nepalensis
- Alnus nitida
- Alnus oblongifolia
- Alnus orientalis
- Alnus pendula
- Alnus rhombifolia
- Alnus rubra
- Alnus serrulata
- Alnus serrulatoides
- Alnus sieboldiana
- Alnus 'Sipkes'
- Alnus × spaethii
- Alnus subcordata
- Alnus trabeculosa
Tree to 35 m. Bark grey to grey-brown, becoming fissured with age. Twigs brown to silvery grey, thin, viscid, pubescent when young. Buds 5–6 mm, obovate, apex rounded, villous, scales 2–3, brown, viscid, stipitate, stipe 4–6 mm. Leaves obovate to suborbicular, 5–9 × 4–8 cm, apex broadly acute to emarginate, base cuneate, margin lobulate with teeth dentate, craspedodromous, 7–10 pairs of lateral veins, blade adaxially ± glabrous, abaxially glabrous to pubescent, always pubescent along veins and with hairy domatia of different colour to veins, light green above and below. Petiole 8–28 × 1–2 mm, glabrous. Staminate catkins in terminal cluster, suberect in bud, pendulous at anthesis, 20–60 × 2–6 mm at anthesis. Pistillate catkins 2–4 in pendent racemose cluster below males, 2 × 1 mm, peduncle 4–20 mm. Fruit ovate-elliptic, 11–21 × 7–15 mm, scales woody, apices rounded with 4 divergent lobes, dark brown to black at maturity, peduncle 35 mm, branchlets 4–13 mm. Seeds wingless, 2 × 2 mm, mid-brown. Flowering February to April. Tetraploid, 2n=56. (Vit et al. 2017).
Distribution Albania Greece Montenegro Serbia
Habitat Stream and riverine forests in mountain valleys and hardwood forests dominated by Fraxinus angustifolia and Platanus orientalis. Associated with frequently flooded alluvia close to the active channels of streams and rivers.
USDA Hardiness Zone 3-7
RHS Hardiness Rating H7
Conservation status Not evaluated (NE)
Alnus rohlenae is a recently described tetraploid species (Vit et al. 2017) from south-eastern Europe, in the western part of the Balkan Peninsula, covering the northern part of Greece, Albania, Montenegro, Serbia and possibly adjacent regions. It is an autopolyploid of A. glutinosa, most likely derived during a period of isolation, probably during glaciation, from refugia in this region. Of note are triploid A. glutinosa and probable hybrids that occur in the same region as diploid A. glutinosa. These populations still retain the emarginate apices typical of the species, but much less so than further north and west, and appear somewhere nearer subspecies barbata. It is allied to A. lusitanica, another tetraploid species also described in the same paper. In overall appearance A. rohlenae is similar to A. glutinosa but smaller in all parts, especially cones. It is distinguished by the hairy domatia (hair floccules) of different colour than the hairs along the lateral veins. The adaxial leaf surface (as well as annual shoots and buds) are markedly hairy, in contrast to the glabrous A. glutinosa.
Alnus rohlenae is rare in cultivation. Plants were introduced by the Belgian Alnus Seed Bank from the Sperchios River valley above Lamia, central Greece. Mature trees can be found in the UK at Ness and Hilliers where they have grown into somewhat unassuming but drought tolerant forms of A. glutinosa.
