Acer hyrcanum Fisch. & Mey.

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John Grimshaw, Ross Bayton and Dan Crowley (2020)

Recommended citation
Grimshaw, J., Bayton, R. & Crowley, D. (2020), 'Acer hyrcanum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-hyrcanum/). Accessed 2020-08-14.

Genus

  • Acer
  • Sect. Acer, Ser. Monspessulana

Other species in genus

Glossary

key
(of fruit) Vernacular English term for winged samaras (as in e.g. Acer Fraxinus Ulmus)
sensu lato
(s.l.) In the broad sense.
subspecies
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.

References

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Credits

John Grimshaw, Ross Bayton and Dan Crowley (2020)

Recommended citation
Grimshaw, J., Bayton, R. & Crowley, D. (2020), 'Acer hyrcanum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-hyrcanum/). Accessed 2020-08-14.

A deciduous shrub or tree to 15 m in the wild. Bark grey brown, irregularly fissuring with age. Branchlets soon glabrous, olive or light brown at first, later reddish brown. Buds ovoid, acute tipped, with many pairs of imbricate scales, brown, margins ciliate. Leaves chartaceous to coriaceous, pentagonal in outline, base cordate to truncate, (three-) five-lobed, 3–10 × 8–12 cm, lobes to half the length of the blade, ovate, lateral lobes spreading, basal lobes smaller, apex obtuse to acute, margins entire to lobulate to dentate, upper surface mid green, lower surface paler, sometimes glaucous, pubescent often along veins and in vein axils; petiole 2–10 cm long, green or red, broadening towards the base; autumn colours yellow to brown. Inflorescence terminal, corymbose, peduncle and pedicels pubescent at first, pendulous, up to 20-flowered. Flowers yellow, 5-merous, sepals obovate, 0.3–0.5 cm long, petals oblong-ovate, longer than sepals, stamens eight, inserted inside the nectar disc. Samaras to 3 cm long, wings spreading variously; nutlets rounded to ovoid. Flowering March to April, with the leaves, fruiting in September to October. (van Gelderen et al. 1994le Hardÿ de Beaulieu 2003Gregory 2007)

Distribution  AlbaniaAzerbaijanBosnia and HerzegovinaBulgariaGeorgiaGreeceIranLebanonNorth MacedoniaMontenegroSerbiaSyriaTurkeyUkraine

Habitat Mixed deciduous and conifer forest, usually on calcareous substrates, between 400 and 2400 m asl.

USDA Hardiness Zone 5-6

RHS Hardiness Rating H5

Conservation status Least concern (LC)

Acer hyrcanum is, on the whole, a complex of rather unexciting Maples from eastern Europe and western Asia that can really only justify their space in specialist collections. It is however a species complex that requires further study. Seven subspecies are recognised by van Gelderen et al. (1994), while a new, closely related species, Acer mazandaranicum, was described from Iran in 2008 (Amini et al. 2008). Like A. undulatum, from southwest Turkey and also attributable to the complex, it is currently absent from collections. The close relationship of this complex to A. opalus and its relatives should be noted.

Examples of the species (sensu lato) can be relatively large, but in many situations it is often rather small and scrubby. All the subspecies prefer a warm site. At least most are in cultivation, and are occasionally offered for sale by specialists such as Plantentuin Esveld, but notable specimens are rare. Impressive examples however, seemingly of the typical subspecies grow at Westonbirt Arboretum, Gloucestershire, and flower prolifically in late March and early April.

A curious observation noted at Hergest Croft is that A. hyrcanum seedlings make a strong root before the cotyledons emerge – apparently an adaptation to drier habitats. The slow-growing tree there is derived from seed collected on Kop Dag in northeastern Turkey, by R.L. Banks in 1982, outside the known range of any of the subspecies, and has not been identified to subspecific level (L. Banks, pers. comm. 2006).

A tentative key to the subspecies as treated by van Gelderen et al. (1994), and at least most of which appear to be in cultivation, is provided below, adapted from Grimshaw & Bayton (2009).

Identification Key

1a.

Tree or shrub to 4–12 m tall; leaves 3–10 cm across, margins flat

2

1b.

Shrub to 2–3 m tall; leaves 0.5–1.5 cm across, margins undulate; Greece, western Turkey

subsp. reginae-amaliae

2a.

Leaves five-lobed, margins coarsely serrate; samaras 3–4 cm long

3

2b.

Leaves three-lobed or with two additional poorly developed basal lobes, margins entire; samaras not over 1 cm long; southern Turkey

subsp. sphaerocarpum

3a.

Branchlets glabrous, or soon becoming so

4

3b.

Branchlets persistently pubescent; Lebanon, western Turkey

subsp. keckianum

4a.

Leaves dark bluish green above

5

4b.

Leaves green above

6

5a.

Leaves tomentose below, lobes abruptly acuminate; Ukraine (Crimea)

subsp. stevenii

5b.

Leaves glabrous, lobes acute to rounded; Albania, Bosnia-Herzegovina, Bulgaria, Croatia, Greece, Macedonia, Serbia & Montenegro

subsp. intermedium

6a.

Small tree or shrub, to 5–6 m tall; leaves slightly tomentose below, deeply incised; Lebanon, western Syria, southern Turkey

subsp. tauricolum

6b.

Tree or rarely shrub, to 10–12 m tall; leaves glabrous, shallowly incised; Asia (Lebanon, western Iran, Turkey), Europe (Croatia, Bosnia-Herzegovina, Serbia & Montenegro)

subsp. hyrcanum

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