Acer metcalfii Rehder

(Sect. Macrantha)


A. sikkimense subsp. metcalfii (Rehder) P.C. de Jong

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New Trees

Tree to 10 m. Bark smooth, snakebark-patterned. Leaves deciduous, thick, 10–14 × 7–11 cm, dark green above, three-lobed, lobes acuminate, margins coarsely serrate; petiole 2–3(–5) cm long. Inflorescence terminal, racemose, with c.15 flowers; flower details unrecorded, but similar to those of A. davidii subsp. grosseri. Samaras 2–2.5 cm long, brownish yellow, wings spreading obtusely. Xu et al. 2008. Distribution CHINA: northern Guangdong, northeast Guangxi, southeast Guizhou, southern Hunan. Habitat Mixed forests between 800 and 1500 m asl. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Taxonomic note The relationships of A. metcalfii are disputed. It was treated as a subsp. of A. sikkimense by de Jong (in van Gelderen et al. 1994), but this view was never entirely satisfactory. It seems to be related to the A. davidii group, differing in its acuminate lobes and serrate margins, and is closest to A. davidii subsp. grosseri according to Chin-sung Chang (in Xu et. al. 2008). The authors of the Flora of China account disagree among themselves, however, as to how these taxa should be recognised.

Acer metcalfii is not well understood, either as a wild tree, where its relationship to the other snakebark species needs resolution, or in cultivation, where trees grown under this name may be wrongly identified. Living material was not known to the authors of Maples of the World, but they commented that it was described by Rehder as being close to A. davidii subsp. grosseri (van Gelderen et al. 1994), and this is how it is now treated in the Flora of China account. There is little material indubitably of A. metcalfii in cultivation, but at Tregrehan there is a 4 m specimen (TROBI), grown as a graft (onto A. davidii) from a seedling collected in southern Hunan by Bob Cherry (K. Rushforth, pers. comm. 2008).

Trees at Hergest Croft grown from Lancaster 962, collected as A. davidii at 3800 m in the Pi River valley in western Sichuan in 1981 (R. Lancaster, pers. comm. 2007), were identified as A. sikkimense subsp. metcalfii by Stephen Spongberg (L. Banks, pers. comm. 2006), but western Sichuan is outside the area in which A. metcalfii is normally considered to occur and the identification should be revisited. Trees from the same gathering also grow at Wakehurst Place. The finest Lancaster 962 at Hergest Croft is approximately 8 m tall (2006) and forms an elegant small tree, most striking in its retention of green bark all the way to the ground. The bark has good pale striations. The leaves are mid-green with a red petiole, but are disappointing in autumn, falling with no significant colour change (unlike A. davidii subsp. grosseri). On the young trees the leaves were quite large, but they have diminished in size with greater maturity. Whatever its real affinity this attractive tree, which can be readily propagated from cuttings, deserves wider distribution (see Figure 10, p. 108).



Other species in the genus