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Dan Crowley (2020)
Crowley, D. (2020), 'Acer komarovii' from the website Trees and Shrubs Online (treesandshrubsonline.
A deciduous shrub or tree to 5 m. Bark smooth, green at first, soon turning brown. Twigs rather slender, glabrous. Buds small, with 2 pairs of valvate scales, purple. Leaves triangular ovate, 6–10 × 6–8 cm, base cordate or subcordate, palmately (3–)5-lobed, upper surface pale green, lower surface pale green with rusty pubescence in vein axils, margins doubly serrulate and lobulate with obtuse teeth, central lobe ovate with an acuminate apex, lateral lobes triangular-ovate, basal lobes ovate with an obtuse apex; petiole 5–7 cm long, glabrous or pubescent, red to purple and slightly grooved; autumn colours yellow to red. Inflorescence terminal, racemose, pendulous, 5–7(–10) flowered, 4–6 cm long. Flowers yellowish-green, 5-merous, usually dioecious; pedicels 0.7–1 cm, sepals ovate-oblong 0.3–0.4 cm long, petals ovate- to obovate-oblong, slightly longer than sepals, stamens eight, inserted outside the nectar disc. Samaras 1–1.2 cm long, wings spreading obtusely; nutlets nearly flattened. Flowering from May to June, fruiting from August to September. (Pojarkova 1974; Xu et al. 2008; de Jong 2019).
Distribution China Jilin; Liaoning North Korea Russia
Habitat Mixed alpine forests from 300 to 1200 m asl.
USDA Hardiness Zone 5
RHS Hardiness Rating H5
Conservation status Least concern (LC)
Taxonomic note This species was treated as a subspecies of Acer tschonoskii by van Gelderen et al. (1994), as A. tschonoskii subsp. koreanum.
Plants that fit Acer komarovii have more often been grown as A. tschonoskii subsp. koreanum. However A. komarovii is considered distinct from that species by Chang & Kim (2003), Xu et al. (2008) and de Jong (2019). A. komarovii differs from A. tschonoskii in several ways: ecologically, being a sub-alpine plant of higher elevations, as well as having a distinct geographical distribution; it flowers around a month earlier, both in the wild and cultivation; its inflorescences are pendulous, as opposed to erect in A. tschonoskii; the leaves of A. komarovii are longer than they are wide, whereas in A. tschonoskii they are (usually) wider than long. (Urosov 1985; de Jong 2019).
Like A. tschonoskii, this species is not grown for its bark but is very hardy, though sensitive to spring frosts. It is worthy of its place in the garden cheifly on account of its attractively coloured red shoots and petioles, and its strong autumn colour. The current UK and Ireland Champion (recorded by The Tree Register as A. tschonoskii subsp. koreanum) grows at the Sir Harold Hillier Gardens, Hampshire, measuring 6.1 m tall in 2017. A contender for the title at Blagdon Hall, Northumberland, measured 6 m tall in 2013 (The Tree Register 2019). Both plants date only from around the turn of the millenium, with few old plants known. It is represented in collections in North America (mostly growing as A. tschonoskii subsp. koreanum) including at The Dawes Arboretum, Ohio and The Morton Arboretum, Illinois as well as at the David C. Lam Asian Garden, Vancouver. The species can also be found in some of the significant maple collections in mainland Europe, such as at Arboretum Wespelaar, Von Gimborn Arobretum and Rogów Arboretum. It was introduced to cultivation in 1917 (Rehder 1940).