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A deciduous tree usually to 10 m, rarely taller. Bark greyish brown, smooth. Branchlets glabrous, purplish red or greenish, sometimes bloomed, turning darker. Buds, ovoid, with four pairs of scales. Leaves broadly pentagonal in outline, base subcordate to truncate, (three-) five lobed, 5–8 × 5–9 cm, lobes apically acute or acuminate, margins sharply serrulate, upper surface mid green, lower surface glossy green, glabrous except for tufts in vein axils; petiole 2.5–6 cm long, red or green, glabrous, autumn colours yellow to orange. Inflorescence, terminal, corymbose. Flowers 5-merous, usually dioecious, pedicels long and slender, sepals and petals oblong to broadly ovate, sepals red, petals white, petals as long as sepals, stamens eight, inserted in the middle of the nectar disc. Samaras 2.5 to 3.5 cm long, wings spreading nearly horizontally. Nutlets ovoid. Flowering May, with unfolding leaves, fruiting in October (van Gelderen et al. 1994; Xu et al. 2008).
Distribution China Anhui, Fujian, southern Gansu, Guizhou, southern Henan, western Hubei, Hunan, Jiangxi, southern Shaanxi, Sichuan, Yunnan, Zhejiang Taiwan (China) Central and northern regions
Habitat Forests and valleys between 1000 and 2000 m asl.
USDA Hardiness Zone 6-7
RHS Hardiness Rating H5
Conservation status Least concern (LC)
A deciduous tree from 12 to 30 ft high; branchlets glabrous and often purplish. Leaves five-lobed, 21⁄2 to 4 in. wide, scarcely so long, truncate or slightly heart-shaped at the base; the lobes ovate, long-pointed, minutely, regularly and sharply toothed; glabrous except for down along the veins and in their axils. Flowers borne at the end of a slender-stalked corymb, 2 in. long. Fruit glabrous; keys 1 in. long; wings 2⁄5 in. wide, spreading nearly horizontally.
Native of Central China; discovered by Henry, and introduced by Wilson for Veitch in 1901 during his first expedition. It is allied to A. sinense, but differs in the smaller more finely and evenly toothed leaves, and in the corymbose inflorescence. In the last character, and in the shape of its leaves, it bears a strong resemblance to the typical form of A. palmatum. But, as seen in gardens, it is well distinguished by its stiffer, more glossy leaves. A closely related species – A. serrulatum Hayata – is found in the island of Formosa (Taiwan); it is common there in mountain forests to an altitude of 7,000 ft and makes a tree of up to 70 ft in height.
A. serrulatum – Mentioned under A. oliverianum, this species has been introduced by Gordon Harris and is doing well in his collection, but needs a sheltered position.
This species was described by Bean (B216) and Krüssmann (K86).
A. serrulatum Hayata
Subsp. formosanum forms a tree to 20 m tall; leaves deeply five-lobed, with central lobe longest, not leathery in texture; samaras ~2.5 cm long, wings spreading obtusely. Typical A. oliverianum forms a small tree or shrub 8–10 m tall; leaves regularly five-lobed, leathery in texture; samaras 3–3.5 cm long, wings spreading almost horizontally. Van Gelderen et al. 1994, van Gelderen & van Gelderen 1999, Xu et al. 2008. Distribution TAIWAN. Habitat Forests between 1000 and 2000 m asl. USDA Hardiness Zone 7–8. Conservation status Not evaluated. Illustration NT96. Cross-references B216, S49 (as A. serrulatum), K86. Taxonomic note Flora of China (Xu et al. 2008) treats this as A. serrulatum, stating that it differs from A. oliverianum in the number of flowers and different flavonoid patterns, but P. Gregory (pers. comm. 2008) maintains the status quo.
Acer oliverianum subsp. formosanum is potentially a rather large and magnificent tree, but as yet all specimens in cultivation are still young. An early introduction was made by Kirkham & Flanagan, who col lected seed at 2210 m in Nantou Co., Taiwan in 1992 (ETOT 64). Material from this source has been widely distributed and trees are generally doing very well, including one specimen at the Hillier Gardens that was 5.1 m tall in 2006, and a flourishing grove at the University of British Columbia Botanical Garden in Vancouver (Flanagan & Kirkham 2005). Other introductions include those by Bleddyn and Sue Wynn-Jones (BSWJ 1891) and Dan Hinkley (DJHT 99081) from more recent trips to Taiwan.
The specimens seen for New Trees all have a distinct elegance, with attractive dark olive-green foliage and greenish stems: the trunk colour when mature is described by Dan Hinkley (Heronswood Nursery catalogue 2005) as ‘a pleasing frosted light green’. The new growth emerges alarmingly early in the year, and can be damaged by light frosts, but usually recovers. The species has a reputation for tenderness (van Gelderen et al. 1994), which may be accurate in continental Europe but is not borne out by experience in the United Kingdom or western North America, when trees have been carefully sited. Growth at the shoot tip continues all summer, the new leaves having a reddish or purple-bronze tinge that can persist on the undersides. In autumn it turns a good yellow, orange or red and holds its leaves late (L. Banks, pers. comm. 2006).