Identifying characteristics:
This is one of Iowa's largest native tree species, growing to 100 feet tall.
It has a broad, spreading, round-topped crown, with drooping branches that
turn upwards at the ends. The trunk is straight, thick and short, often
dividing near the ground and often more than 4 feet in diameter. Leaves are 3 to 6 inches long, opposite,
simple, and palmately 5-lobed. Margins are irregularly double-toothed. The
leaf surfaces are glabrous, light green above and white to silvery below,
giving it the common name "silver maple." Fall coloring is green
to yellow-brown, and is not striking. This species is the first native tree
in Iowa to flower in spring, with the flowers appearing in March before
the leaves. The tiny, apetalous, yellowish-green male and female flowers are covered by red bud
scales and occur in separate clusters on the same tree. Fruits
are winged samaras which ripen and fall in late spring. The paired samaras
are joined at a 90 degree angle, hang on a slender stalk and the wings are
1.5 to 3 inches long. Silver maples have the largest fruits of all native
maples. One seed of each pair is usually aborted, and viable seeds are able
to germinate as soon as they fall, taking advantage of nutrient-rich silt
deposited from spring flooding. The V-shaped leaf scars have 3 bundle
scars, and a fine line around the twig joins opposing leaf scars. Buds
are covered with bright red to purplish-red scales, which are finely hairy
along the margins. Flower buds are globose and occur in conspicuous clumps.
The gray-brown bark is smooth
on young trees, later developing irregular furrows with thin, gray, scaly
plates.
Similar species:
Ecology:
Distribution: The silver maple is native from Quebec to Florida,
west to Oklahoma, Kansas and Nebraska. The largest trees occur in
the lower Ohio River Valley. It is native throughout Iowa.
Habitat: This is a lowland species, found on stream banks, floodplains and near lakes and ponds, withstanding short periods of flooding. It grows best in deep, moist, slightly acid soils, but will tolerate a variety of soil conditions. It grows rapidly for the first 25 to 30 years and seldom lives longer than 140 years. The silver maple is susceptible to pests and diseases. In wet weather anthracnose may become serious; the weak wood often leads to fungal infection after storm breakage; and manganese chlorosis in alkaline soils causes yellowing of the leaves. Other problems include Verticillium wilt, root rot, leaf spot, powdery mildew, canker, leaf scorch, cottony maple scale, borers and tent caterpillars.
Uses:
Wood: The wood is moderately important. The wood is
softer than that of the sugar (or "hard") maple and it is often
referred to as "soft maple." It is medium-lightweight but brittle,
and is used for boxes, crates, veneer, inexpensive furniture and many other
uses. Although the sugar grade of the sap is superior to that of the sugar
maple, the yield is not abundant and therefore not commercially viable.
Wildlife: The silver maple is a useful forest tree to many wildlife species. Squirrels, rodents and birds (particularly pine and evening grosbeaks) eat the seeds; deer eat the young twigs and foliage; and hollow trunks serve as dens for raccoons and squirrels.
Horticulture: Due to its fast growth, handsome form and adaptability, this tree has been a favorite shade tree for planting in Iowa. The fast growth comes with a liability: limbs are easily broken by heavy, wet spring snows, leading to wood decay. The silver maple is best planted only in difficult sites where other native trees cannot survive as other native maples have superior fall color and sturdiness qualities. 'Silver Queen,' is an upright, seedless, form with yellow fall-foliage. 'Laciniatum' has deeply divided leaves.
