Acer pilosum Maxim.

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Credits

Dan Crowley (2026)

Recommended citation
Crowley, D. (2026), 'Acer pilosum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-pilosum/). Accessed 2026-07-11.

Family

Sapindaceae

Genus

Acer
Sect. Pubescentia

Common Names

Soft-haired Maple

Infraspecifics

var. stenolobum

Other taxa in genus

Glossary

variety: (var.) Taxonomic rank (varietas) grouping variants of a species with relatively minor differentiation in a few characters but occurring as recognisable populations. Often loosely used for rare minor variants more usefully ranked as forms.

References

Credits

Dan Crowley (2026)

Recommended citation
Crowley, D. (2026), 'Acer pilosum' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/acer/acer-pilosum/). Accessed 2026-07-11.

Acer pilosum forms a small tree, with an open branch structure and rough bark (Arboretum Het Leen Eeklo, Belgium – 8 August 2024). Image © Jan De Langhe.

A deciduous tree to 5 m. Bark brown. Branchlets slender, glabrous, brown. Buds small, brown, ovoid, with 6–10 pairs of scales, pubescent along their margins. Leaves deciduous, broadly pentagonal in outline, base cuneate to truncate, deeply 3-lobed with 3 primary veins, 3–8 × 2.5–12 cm, lobes oblong-lanceolate, apically obtuse to acute, margins entire or remotely toothed, with few serrations or dentate apically, upper surface dark green, lower surface paler, glabrous or pubescent along veins; petiole 1.5–3 cm long, green to red, glabrous or pubescent. Plants usually andromonoecious, inflorescence corymbose on terminal or lateral shoots, few- or many-flowered, 5-merous, peduncles 1–1.5 cm, sepals ovate, sparsely ciliate, petals narrowly oblong, glabrous, stamens 5 or 6, inserted on the outside of the slightly lobed nectar disc, ovary shortly pubescent. Samaras 2–2.5 cm long, wings spreading acutely to nearly horizontally. Nutlets rounded. Flowering in April or May, fruiting September to October (van Gelderen, de Jong & Oterdoom 1994; van Gelderen & van Gelderen 1999; Xu et al. 2008).

Distribution China Gansu, southwestern Nei Mongol, southeastern Ningxia, Shaanxi, Shanxi

Habitat Forests between 1000 and 2000 m asl.

USDA Hardiness Zone 5

RHS Hardiness Rating H7

Conservation status Data deficient (DD)

Little documented, Acer pilosum was seemingly first discovered in the plains of southern Gansu by Pavel Piasezki in 1875 (Bean 1976). The first introduction of this species appears to have belonged to var. stenolobum (see below). Material not attributed to that variety is present in a small number of collections, though may still belong to it. A plant at the Arnold Arboretum, Massachusetts recorded as A. pilosum was grown from material collected by the 2005 NACPEC Gansu expedition under NACPEC05 071 (American Public Gardens Association 2017), though appears since lost (Arnold Arboretum 2018).

Foliage on Acer pilosum, from a tree at Arboretum Het Leen Eeklo, Belgium (8 August 2024). Image © Jan De Langhe.

Acer pilosum leaves, the lamina variable 3-lobed (Arboretum Het Leen Eeklo, Belgium – 8 August 2024). Image © Jan De Langhe.

Slender, brown twigs on Acer pilosum, note the numerous bud scale scars and the brown conical buds with apically pubescent scales (Arboretum Het Leen Eeklo, Belgium – 8 August 2024). Image © Jan De Langhe.

The lower lamina surface of Acer pilosum is smooth, except for a few hairs in the basal vein axils (Arboretum Het Leen Eeklo, Belgium – 8 August 2024). Image © Jan De Langhe.

Acer pilosum grey-brown bark, peeling off in narrow chunks (Arboretum Het Leen Eeklo, Belgium – 8 August 2024). Image © Jan De Langhe.

var. stenolobum (Rehder) W.P. Fang

Synonyms
Acer stenolobum Rehd.
Acer stenolobum var. megalophyllum W.P. Fang & Y.T. Wu
Acer stenolobum var. pubescens W.Z. Di.

The leaves of var. stenolobum have shorter lobes than in var. pilosum, which are only 0.5 cm wide (2.5 cm in the type variety). The samaras are 2–2.5 cm long with wings spreading at an obtuse or right angle (van Gelderen, de Jong & Oterdoom 1994; van Gelderen & van Gelderen 1999; Xu et al. 2008).

Distribution China northeast Gansu, southwest Nei Mongol, southeast Ningxia, northern Shaanxi

RHS Hardiness Rating: H7

USDA Hardiness Zone: 5-6

Var. stenolobum was described as a species by Alfred Rehder in 1922 and reduced to a variety of A. pilosum by Prof. Fang in 1966 (van Gelderen, de Jong & Oterdoom 1994). One of the rarest maples in cultivation, all stock being said to be derived from a tree at the Arnold Arboretum introduced by William Purdom in 1911 (van Gelderen, de Jong & Oterdoom 1994; van Gelderen & van Gelderen 1999). It makes a small tree of no great beauty, although the angular leaves can turn a reasonable red in autumn. It is cultivated in the major maple collections in Europe as well as North America, where it is fully hardy, but it would benefit from reintroductions both to establish whether it really is distinct, and to ascertain whether it posseses any hitherto hidden ornamental qualities. The current UK and Irish Champion is a plant of 2 m tall at Batsford Arboretum, Gloucestershire (The Tree Register 2025).

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