Acer hyrcanum Fisch. & Mey.

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Credits

John Grimshaw, Ross Bayton & 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 2020-11-29.

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 & 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 2020-11-29.

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, (3-) 5-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 8, inserted inside the nectar disc. Samaras to 3 cm long, wings spreading variously; nutlets rounded to ovoid. Flowering from March to April, with the leaves, fruiting from 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 2400 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 Amini, H. Zare & Assadi, was described from Iran in 2008 (Amini et al. 2008). Like A. undulatum Pojark., 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 glabrus, shallowly incised; Asia (Lebanon, western Iran, Turkey), Europe (Croatia, Bosnia-Herzegovina, Serbia & Montenegro)

subsp. hyrcanum


subsp. intermedium (Pančić) Bornm.

Synonyms
Acer hyrcanum var. cordisectum (Borbas) Bornm.
Acer intermedium Pančić
Acer italum var. serbicum (Pax) Pax
Acer intermedium var. cordisectum Borbas
Acer italum f. cordisectum (Borbas) Pax

Subsp. intermedium is a large shrub with glabrous leaves 3–8 cm wide with coarsely toothed, acute to rounded lobes and glaucous lower surfaces. (van Gelderen et al. 1994Grimshaw & Bayton 2009).

Distribution

  • Albania
  • Bosnia and Herzegovina
  • Bulgaria
  • Croatia
  • Greece
  • North Macedonia
  • Montenegro
  • Serbia

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

This subspecies is unsurprisingly scarce in collections. A specimen determined as such by the late Peter Gregory grows at Westonbirt Arboretum, Gloucestershire, though its origins are unknown.


subsp. keckianum (Pax) Yalt.

Synonyms
Acer italum var. keckianum Pax
Acer hyrcanum f. tomentellum (Pax) Simonkai

Subsp. keckianum is a small tree or shrub that has leaves 3–6 cm wide, lobulate and coarsely toothed, branchlets and leaf undersides tomentose, petioles often very short or sessile. (van Gelderen et al. 1994).

Distribution

  • Lebanon
  • Turkey

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

The most useful character for separating subsp. keckianum from subsp. tauricolum is that the former has pubescent branchlets, even late in the season, whereas those of the latter are glabrous. The character of very short, or even sessile leaves as stated by van Gelderen et al. (1994) appears less consistent. CBDK 29, 33 and 85, collected from Lebanon in November 2011 as Acer sp. fit subsp. keckianum inspite of their long petioles; their pubescent branchlets evident on their respective herbarium specimens at RBG Edinbugrh. CBDK 29 has grown steadily at Westonbirt Arboretum (as subsp. tauricolum), in a position in full sun, though on somewhat heavy soil.


subsp. reginae-amaliae (Orph. ex Boiss.) A.E. Murray

Synonyms
Acer reginae-amaliae Orph. ex Boiss.
Acer monspessulanum var. reginae-amaliae (Boiss.) Wesmael
Acer orientale f. quniquenerve Vierhapper

Subsp. reginae-amaliae is a shrub or small tree to 8 m in the wild. Its leaves are 0.5–1.5 cm across, with slightly serrate margins, basal lobes sometimes absent. (van Gelderen et al. 1994).

Distribution

  • Greece
  • Turkey

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

While the leaves of some of these subspecies can be quite large and coarse, the distinction of having the smallest leaves in the genus goes to subsp. reginae-amaliae, from arid places in Greece and Turkey (van Gelderen & van Gelderen 1999), which would make an interesting shrub for a dry bank. A specimen of it, as of 2009, was doing very well at Blagdon, Northumberland. Amalia of Oldenburg (1818–1875) was Queen Consort of King Otto of Greece until they were deposed in 1862. She is recorded to have been interested in horticulture, agriculture and viticulture, and was responsible for laying out the gardens of the royal palace in Athens (Wikipedia 2007). Her successor, Queen Olga, is commemorated by the autumn-flowering snowdrop Galanthus reginae-olgae – which would grow well on the same dry bank as the maple (Grimshaw & Bayton 2009).


subsp. sphaerocarpum Yalt.

Subsp. sphaerocarpum is a densely branched shrub with leaves 3–5 cm across, basal lobes often poorly developed and margins entire. Fruits with samaras not longer than 1 cm. (van Gelderen et al. 1994; Grimshaw & Bayton 2009). 

Distribution

  • Turkey

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

The tiny fruited subsp. sphaerocarpum appears to be the only taxon within the species not represented in cultivation, though it would not be a great surprise to discover that it is in fact lurking, undetermined, in a warm corner of a collection in our area.


subsp. stevenii (Pojark.) A.E. Murray

Synonyms
Acer stevenii Pojark.

Subsp. stevenii is a shrubby tree to 4 m, with leaf lobes acuminate and veins pilose on the underside. (van Gelderen et al. 1994).

Distribution

  • Ukraine

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

Also scarce in collections, at the Rogów Arboretum, Poland, subsp. stevenii from the Crimea has formed a slow-growing small tree (P. Banaszczak, pers. comm. 2007). It is also represented at Westonbirt Arboretum, Gloucestershire. Both appear to be of unknown origin.


subsp. tauricolum (Boiss. & Blanche) Yalt.

Synonyms
Acer tauricolum Boiss. & Blanche
Acer reygassei Boiss. & Blanche
Acer hyrcanum var. reygassei (Boiss. & Blanche) Boisser
Acer italum var. tauricolum (Boiss. & Blanche) Pax

Subsp. tauricolum is a shrub or small tree to 6 m in the wild. Branchlets glabrous. Leaves, 5–10 cm across, deeply incised and slightly tomentose beneath at first, later glabrous. Lobes are apically acuminate and coarsely toothed and its petioles long. (van Gelderen et al. 1994Grimshaw & Bayton 2009). 

Distribution

  • Lebanon
  • Syria
  • Turkey

RHS Hardiness Rating: H5

USDA Hardiness Zone: 4-5

At Wakehurst Place there is a tree of subsp. tauricolum grown from seed from the Flanagan & Pitman expedition to Turkey in 1990 (TURX 99), collected at 1670 m in the Amanus Mountains, Hatay Province, where the parent trees were up to 25 m tall. A specimen from the same collection at the Hillier Gardens was 3.6 m in 2005. CBDK 29, 33 and 85, collected in Lebanon in 2011, belong to subsp. keckianum rather than to subsp. tauricolum – they may be found growing in some UK collections.