A deciduous tree up to 60 ft in height, young shoots not downy, becoming grey and slightly fissured the second year. Leaves five- or seven-lobed, 3 to 6 in. across, and rather more in length, the lobes ovate-triangular, ending in a long, narrow apex, the lowest pair spreading outwards; the base of the leaf is heart-shaped, the margins not toothed; the stalk has a milky sap, and both surfaces are green and glabrous except for tufts of hairs in the vein-axils beneath. Flowers appearing in April or early May with the first leaves, greenish yellow, in corymbose racemes 2 to 3 in. long. Fruit with glabrous wings, about 11⁄2 times as long as the nutlets, the pairs spreading almost horizontally or ascending; less commonly they are parallel and almost connivent (f. connivens (Nichols.) Rehd.); each key 3⁄4 to 11⁄4 in. long.
Native of Japan, Manchuria, N. and Central China, and Pacific Russia; introduced by Maries from Japan in 1881 under Thunberg's name A. pictum, published in 1784. This cannot stand, since Thunberg had used it a year earlier for a plant that was not a maple at all but the member of the aralia family now known as Kalopanax pictus (Acanthopanax ricinifolium). Maximowicz's name is in any case much to be preferred: the type of A. pictum was in fact a garden tree with variegated leaves (hence the epithet chosen) and had the wings of the fruit connivent, although this form is not common in the wild state of the species. The typical A. mono was introduced in 1901 by Wilson, when collecting in China for the Veitch nurseries, but had reached cultivation on the continent some years earlier by way of St Petersburg.
A. mono is a handsome tree, resembling A. cappadocicum (q.v. for the differentiative character), but is rarer in cultivation; most trees going under the name “A. pictum” are really A. cappadocicum. In the wild state, A. mono varies somewhat in the size, shape and indumentum of the leaf.
f. ambiguum (Dipp.) Rehd. A. ambiguum Dipp. – Leaves downy beneath, lobes five, the centre one triangular ovate and much longer than the laterals. Origin uncertain.
cv. 'Marmoratum'. – Leaves powdered over with white dots and stains, some being more white than green. Described by Nicholson in Gard. Chron., Vol. 16, 1881, p. 375, as A. pictum marmoratum. It was probably growing at Kew at that time but is no longer in the collection. In the same article, Nicholson described an A. pictum variegatum, but it is not clear whether the account was based on a living tree or on Thunberg's original figure of A. pictum, which, as pointed out above, was based on a garden tree with variegated leaves.
var. mayrii (Schwer.) Nemoto A. mayrii Schwer. – A tree with smooth, white bark; branchlets usually glaucous and remaining smooth in their second year, as in A. cappadocicum, and then yellowish or brown. Leaves rounded, with very short, broad lobes. Native of Japan in Hokkaido and the northern part of the main island. Probably not in cultivation at present.
var. tricuspis Rehd. A. tenellum Pax – A tree to 25 ft high. Leaves thin and papery, three-lobed (the smaller ones ovate, not lobed), 2 to 3 in. long and as much or a little more wide, base truncate or heart-shaped; lobes triangular, pointed or bluntish. Leaf-stalk slender, 1 to 3 in. long.
Native of Szechwan, China; discovered by Henry about 1888 and introduced by Wilson in 1901 under W. 863. It is a very distinct maple on account of its thin, smooth, cleanly cut, three-lobed leaves, whose long, slender stalks cause them to be restless as those of an aspen. It is rare in gardens. The late Sir Frederick Stern had a fine specimen at Highdown near Worthing; it was destroyed in a gale some years ago but is survived by several younger trees raised from its seed.
A. fulvescens Rehd. – A tree to 70 ft high in W. Szechwan, China. It differs from A. mono chiefly in its leaves, which are almost invariably three-lobed and clad beneath with a yellowish down that darkens to rust-coloured as they mature; branchlets dark brown and smooth the first year, silvery grey and roughish in the second. Introduced by Wilson in 1908, but so rare that the only specimen known to us is at Borde Hill, Sussex. This is 30 ft high, branching at 3 ft, where it is 31⁄2 ft in girth. It makes a very handsome, bushy tree of mushroom-like habit.
From the Supplement (Vol. V)
The first of the above synonyms represents Dr Murray's original view. Subsequently (Kalmia, Vol. 8, p. 5), he submerged A. mono in A. truncatum and made the latter a subspecies of A. cappadocicum. However, de Jong considers A. truncatum and A. mono to be two distinct species.
A. mono is uncommon in cultivation, but there is a fine specimen at Hergest Croft, Herefordshire, measuring 82 × 73⁄4 ft at 3 ft (1985). Two examples at Kilmun, Argyll, planted 1935, measure 50 × 3 ft and 46 × 43⁄4 ft at 2 ft (1978). They were received under the Japanese name for the species – 'Itaya-kaede'. In Eire there is a good specimen at Birr Castle, Co. Offaly, of 69 × 73⁄4 ft (1985).
A. mono was reintroduced to Kew in 1982 from Mount Pukhan, north-west of Seoul, South Korea (B.E. & C. 226).
A. fulvescens – The Borde Hill tree measures 34 × 41⁄4 ft (1981); there is another example at Arley Castle, Worcestershire. It is doubtful whether A. fulvescens can be maintained as a species distinct from A. mono.
† A. okamotoanum Nakai – A near ally of A. mono, differing chiefly, according to Fang, in its large fruits, with nutlets 5⁄8 in. wide, and wings up to 2 in. long. Native of Ullung-do (Dagelet Island) off the east coast of Korea.