4. Acer saccharinum L. (silver maple, soft maple)

Pl. 196 g–l; Map 807

Plants monoecious, medium to large trees to 30 m tall with ascending to spreading branches, the bark of young trees smooth and light gray, becoming separated into long thin plates and ridges on older trees. Twigs red to yellowish brown, the winter buds elliptic-ovate, blunt at the tip, with 6–10 overlapping scales. Leaf blades 8–15 cm long, broadly triangular-ovate in outline, the undersurface silvery white and glabrous or sparsely hairy when young, with 5 deep main lobes, these tapered to sharply pointed tips and with the sinuses usually angled or V-shaped (occasionally those of individual leaves appearing bluntly angled to nearly rounded), the lateral lobes cut 1/2–2/3 of the way to the base, the central lobe noticeably narrowed toward the base, the margins toothed and with smaller lobes. Inflorescences produced before the leaves; small, dense, staminate and pistillate clusters from lateral buds along the branches; the flowers sessile or very short-stalked (the stalks elongating greatly after flowering as the fruits mature). Calyces 4–6 mm long, the sepals fused with only 5 shallow lobes apparent, yellowish green, sometimes grayish pink when young. Corollas absent. Staminate flowers with (3–)5(–7) stamens and lacking a nectar disk. Pistillate flowers with the ovary densely hairy. Fruits dispersing before the leaves are mature, the samaras 3.5–7.0 cm long, glabrous or sparsely hairy, the wings 3.5–6.5 cm long, spreading at about 90–120° and slightly incurved. 2n=52. January–April.

Scattered to common nearly throughout the state (eastern U.S. west to South Dakota and Oklahoma; Canada). Bottomland forests, mesic upland forests in ravine bottoms; banks of streams and riverbanks, and margins of ponds and lakes; also roadsides, ditches, vacant lots, and moist, open, disturbed areas.

The leaves of A. saccharinum turn yellow in the autumn. The twigs produce a disagreeable odor when bruised or broken. The species forms huge often nearly monocultural stands in disturbed bottomland forests and on the river sides of levees in the Big Rivers Division, and it often colonizes gravel bars along larger streams and rivers elsewhere in the state.

The wood of silver maple is of minor commercial importance regionally for use in making furniture and as pulpwood for paper. The sap has also been used to a small extent for maple syrup production. However, the species is extremely important horticulturally as a shade tree, both because of its beauty and its ability to grow quickly into a large tree. Drawbacks to its cultivation are the tendency of older, brittle branches to break during storms and the large crop of seeds that germinate to become weeds in gardens, alleys, and vacant lots. It is also somewhat prone to attack by insect pests and is considered by foresters to have a relatively short average life span for a maple species.