Acer saccharinum

Native

Bottomland forests, river banks, stream banks, flood plains, and lake edges.

Late February to early May

Greenish-yellow

40′ to 70′

This is a fast-growing, moderately short-lived, deciduous, medium to large tree rising on a single trunk from shallow, fibrous roots. In Minnesota mature trees are usually 40′ to 70′ tall and up to 36″ in diameter, though large individuals can reach over 90′ in height. They typically live 100 to 130 years.

The crown is rounded. The trunk is straight and much branched. In the forest the trunk is straight and tall. In the open it is split near the ground into a few branches that ascend sharply.

The branches are opposite, short, sturdy, and ascending to spreading. Larger branches arch outward and droop downward, but ascend at the tip.

The bark on young trees is light gray and smooth. On mature trees the bark is dark reddish-brown and is separated into long vertical plates that are attached in the middle but loose at the top and bottom.

The twigs are thin, yellowish-gray to reddish-brown, smooth, hairless and shiny. They emit an disagreeable odor when bark is bruised or scraped. They appear in a V-shape on the branches. The younger twigs have obvious, small, lighter, pore-like openings (lenticels) that are not raised much above the bark surface. At the end of the twig is a brown, ¼″ to ⅜″ long, sharply pointed terminal bud with tight scales. The leaf scars have bundle scars. The sap is clear, not milky.

The buds are dark brown, egg-shaped to elliptic, ¼″ long, and blunt at the tip. They are composed of 6 to 10 dark red overlapping scales. The terminal bud is red and relatively short.

The leaves are opposite, stalked, 4″ to 6″ long, and nearly as wide. There are no prominent stipules at the base of the leaf stalk. The blades are palmately lobed with 5 deep main lobes. The lobes taper to sharply-pointed tips and sometimes have smaller, secondary lobes. The leaves of silver maple are more deeply lobed than those of any other maple in Minnesota. The lateral lobes are cut ½ to ⅔ of the way to the base. The space between the lobes (sinus) is angled or V-shaped. The two bottom lobes are much smaller than the two lateral lobes. The central lobe noticeably narrows, with concave sides, toward the base. The sinus at the base of the leaves is open and the two bottom lobes do not overlap. The upper surface is light green and hairless. The lower surface of mature leaves is silvery white and hairless, but green and sometimes hairy when young. The margins have a few coarse, sharp, irregular teeth. The sides and tip of the leaf do not droop. In the fall the leaves turn yellow. Fallen leaves break down quickly.

The inflorescence is a tassel-like cluster of 8 to 14 flowers at or near the tip of the branches.

Male and female flowers are borne on the same tree and but in separate clusters. They appear identical, having both stamens and pistils, but usually only one of the organs is functional. They are greenish-yellow and are on short stalks. They are produced in late February to early May, long before the leaves appear. This is the earliest maple to flower. The flowers are pollinated by wind and bees.

The fruit is a pair of dry seed cases with papery wings attached (double samara). The samaras (or keys) occur in clusters that droop downward from 1″ to 3″ long stalks. The stalks are longer than the wings. The seed cases are plump, attached the the stalk, and slightly connected to each other. The wings are typically 1¼″ to 2½″ long, ¼″ to 7 ⁄16″ wide, diverge at a 90° to 120° angle, and are somewhat curved inward. Usually only one seed case contains a single, viable seed, although sometimes both contain seeds, sometimes both are empty. The keys are hairless or sparsely hairy, green initially, turning yellowish green when the seeds are mature, then brown. They fall in the late spring before the leaves are fully mature. Paired keys mature and are shed individually.

The champion silver maple in Minnesota is on private property in Spring Grove, in Houston County. In 2009 it was measured at 90′ tall and 272″ in circumference (86½″ in diameter).