A deciduous tree 40 to 70 ft high, with a trunk 2 to 3 ft. in diameter, forming a wide-spreading head of branches; branchlets glabrous. Leaves long-stalked, pinnate, 6 to 10 in. long, consisting of three or five leaflets. Leaflets ovate, 2 to 4 in. long, pointed, coarsely toothed towards the end; upper side bright green, glabrous; lower one slightly downy or eventually glabrous; the terminal leaflet often three-lobed or even trifoliolate. Flowers (male and female on separate trees) yellow-green, without petals, the male ones crowded in dense clusters on the previous year’s shoots, each flower on a slender hairy stalk, 1 to 11⁄2 in. long; the females in slender, drooping racemes. Fruit in pendent racemes, 4 to 8 in. long; each key 1 to 11⁄2 in. long, with a wing 1⁄4 to 1⁄3 in. wide, the pair forming an angle of 60° or less.
Native of N. America, where it is widely spread. According to Sargent it is most common in the Mississippi Valley, but reaches as far north as New York State, and as far west as the inland slopes of the Rocky Mountains. It was cultivated by Bishop Compton at Fulham in 1688. Although the typical form is by no means common, it is a handsome tree, especially when isolated on a lawn. It is one of the maples that yield sugar in America. There is a tree 45 × 81⁄4 ft at Kew but this is exceeded in height by one at Northerwood House, Hants, 52 × 3 ft (1963). In Späth’s nursery, near Berlin, there was once a specimen 60 ft high and 61⁄2 ft in girth of trunk.
cv. ‘Auratum’. – Leaflets wholly yellow; this variety is one of the best of golden-coloured trees, and retains its colour until autumn. Branchlets green with a white bloom. Späth’s nurseries, 1891, where it arose as a sport from a variegated form known as ‘Aureo-limbatum’. G. Krüssmann, in Handbuch der Laubgehölze, points out that this clone is not the same as ‘Odessanum’, as has commonly been assumed.
cv. ‘Aureo-marginatum’. – Leaflets marked as in the common variegated box elder but with yellow instead of white. Dieck’s nurseries before 1885.
var. californicum (Torr. & Gray) Sarg. – Differs from the type in the dense covering of grey down beneath the leaves, and by the downy branchlets and fruits. Native of California. Forms intermediate between this variety and the type are said to occur in Arizona, Texas, Missouri, etc. This variety should not be confused with A. negundo californicum Hort. (var. pseudo-californicum Schwer.), which appears to be no more than a strain, in cultivation since before 1864, characterised by its great vigour and by having the young branchlets green, as in the type, but covered with a pruinose bloom, as in var. violaceum.
cv. ‘Crispum’. – Leaflets curled, often deformed; shrubby. In cultivation before 1825. A male clone. See Loudon, Arb. et Frut. Brit., Vol. 1, p. 460.
cv. ‘Elegans’. – Leaves glossy green, with a broad margin of yellow; young growths with a bluish bloom. Apparently of French origin and put into commerce as A. n. aureomarginatum elegans.
cv. ‘Heterophyllum’. – Leaflets reduced to a linear or lanceolate shape, and with more or less deeply cut margins. Späth’s nurseries, 1883.
cv. ‘Odessanum’. – Leaves golden yellow as in ‘Auratum’ (q.v.), but the branchlets densely downy; put into commerce by Rothe’s nursery, Odessa, Russia, in 1890; in cultivation on the continent.
cv. ‘Variegatum’. – One of the commonest of variegated trees, once largely used in town gardens and grown in pots for the decoration of halls and large rooms. The leaflets have an irregular border of white, or are sometimes wholly white. It first appeared as a sport on the green-leaved type in a nursery at Toulouse in 1845, but trees of a large size appear to be very uncommon. It is female, and the fruits are variegated like the leaves.
var. violaceum (Kirchn.) Jäg. – Young branchlets purplish, covered with a glaucous bloom. Such forms are common in the Middle West of the United States.