A tree 30 to 65 ft high, of rounded habit, sometimes much smaller or even bushy; branchlets glabrous. Leaves 21⁄2 to 41⁄2 in. wide, somewhat less in length, shallowly five-lobed, heart-shaped at the base, irregularly toothed; dark green, glossy and glabrous above, paler and more or less downy beneath, especially along the chief veins and in their axils, occasionally quite glabrous; lobes angular. Flowers yellow, appearing in March, numerously crowded in short-stalked corymbs; each flower on a slender, glabrous, pendent stalk, 1 to 11⁄2 in. long. Fruit glabrous; keys 1 to 11⁄2 in. long; wings 2⁄5 in. wide, varying considerably in divergence.
Native of S. and Central Europe; introduced in 1752. It is one of the most ornamental of early-flowering trees, producing its blossoms regularly and in great abundance in March and April; they are of a clearer and more pronounced yellow than in most maples. There are several good specimens at Kew, the largest 50 × 6 ft (1965). At Westonbirt there are two off the Broad Drive, 60 × 71⁄2 and 53 × 41⁄2 ft (1966). There is much confusion in the nomenclature of this maple. It is very variable and some authorities have separated the following varieties from it as distinct species:
var. obtusatum (Willd.) Henry A. obtusatum Willd. – Leaves on the whole larger than in the type, and up to 51⁄2 in. wide, the lobes more rounded and the whole under-surface covered with a close down; flower-stalks hairy; fruit-wings not so large as in var. tomentosum. Native of Central and E. Europe. There is an old specimen at Kew 48 ft high, on a trunk measuring 9 ft in girth at 3 ft.
var. tomentosum (Tausch) Rehd. A. opulifolium var. tomentosum Tausch; A. neapolitanum Ten.; A. opalus var. neapolitanum (Ten.) Henry – Leaves up to 6 or 7 in. wide, covered with a pale felt beneath, the lobes quite shallow, especially the basal ones. Flower-stalks hairy, remaining so until the fruits ripen. Native of the country about Naples, where, like the type farther north in Italy, it is largely employed in vineyards as a support on which to train the vines. There is an example of this variety at Westonbirt, off the Broad Drive, measuring 64 × 61⁄2 ft (1966).