Silver Maple is a large, stout deciduous tree with a short thick trunk that has a few large forks near the ground and an open spreading rounded crown of long curving branches. The tree can reach 100 feet in height and a trunk diameter of over 3 feet.
Bark is light gray, smooth when young and becoming, with age, furrowed into long thin shaggy ridges and strips that frequently have one end loose.
Twigs are also stout, slightly drooping, light green to reddish brown in color, hairless, with white lenticels and have a slight unpleasant odor when crushed. Buds are reddish-brown with large scales, usually clustered together, looking the same as the Red Maple.
Leaves are opposite, simple, up to 5 inches long, with a long stalk, and deeply 5-lobed with the middle lobe often divided into 3 lobes. Lobes are pointed with irregular coarse teeth on the margins and a main vein from the base for each lobe. These lobes are the deepest of the native maples. The upper side is dull green and the under silvery white.
Flowers: The tree is monoecious, that is with separate male and female flowers. Trees with perfect flowers are known but rare. The 1/4 inch flowers are reddish, turning greenish-yellow and occur in dense clusters of separate sexes before the leaves appear in late winter to early spring - one of the earliest flowering species. Male flower clusters are on short lateral spur twigs. They have 4 sepals, no petals and 4 to 6 stamens with several small bracts at the base. Likewise the female flowers have small bracts below the 4 sepals, pistil and two styles.
Fruit: Female flowers mature to a one-seeded samara with a broad wing that is paired with another, the total up to 2-1/2 inches long, green initially and turning light brown. These mature in early summer and drop from the tree, are wind dispersed and can germinate immediately. Trees require about 11 years to produce seed.
Habitat: Silver Maple in native habitat prefers moist soils such as moist woods, floodplains and riparian areas with full sun. It is not tolerant of shade on poorer sites and is a pioneer dominant canopy species. Seedlings can easily be transplanted and it will re-sprout from a stump. It adapts well to the landscape and has long been used as a landscape shade tree. Some consider the form to be poor but as a free standing specimen the shape is comely. The root system however, is shallow and fibrous and lateral roots which extend great distances will occasionally surface. It is a preferred nesting tree for Baltimore Orioles. Silver Maple grows rapidly and the branches are somewhat brittle, scattering twigs and small branches in windstorms as the tree is quite good at self-pruning, similar to Green Ash and Rock Maple.
Names: The genus, Acer, is the Latin word for 'maple'. The species name, saccharinum, just like the species name saccharum of the Sugar Maple, means sweet, referring to the sap. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. Botanists have recently moved the maples into the Sapindaceae family from the older Aceraceae family. The common name of "Silver" maple refers to the light color of the leaf underside.
Comparisons: This tree most easily compares with Red Maple, A. rubrum, which also drops its seeds in the spring, but that tree has smaller leaves that are not as deeply lobed and have more regular teeth and the new samaras turn red.
Above: Silver Maple. The open spreading crown in a winter view. 2nd photo - in summer. 3rd photo - a typical short, thick trunk with forking main branches above. Mature bark has scaly strips. This tree is approx. 130 years old.
Below: Twigs are reddish brown with lenticels. Buds are reddish brown with large scales similar to Red Maple. Seeds develop in paired samaras, already fully formed when the leaves develop (2nd photo) and when mature (brown color - 3rd photo) fall from the tree in early summer.
Above: A cluster of female flowers. The flowers are on short stalks. They have 4 sepals and a pistil with 2 styles.
Below: A typical leaf showing the five lobes. Note the main lobe appears to have 2 smaller side lobes. Silver Maple leaves have the deepest cut lobes of the maples. 2nd photo: Reddish male flowers are in tight clusters and have numerous stamens.
Below: A leaf comparison of the common maples. Images not to scale.
Notes: Silver Maple is not indigenous to the Garden. The first planting was by Eloise Butler in April 1917 when she planted one on the south hillside near the Garden Office. She obtained it from the Park Board Nursery, which at the time was located close by in Glenwood Park. Martha Crone reported planting it in 1934 along with some other species from the Park Board Nursery. Susan Wilkins added others in 2010.
In North America the tree is found in Canada in Saskatchewan, Ontario and Quebec. In the U.S. it is found from the central plains eastward except Texas. There is scattered reporting of it also in several western states. Within Minnesota it is widespread, occurring in the majority of counties in the eastern half of the state and many in the SW quadrant; mostly absent in the west and NW.
Eight species of Maple are found in the wild in Minnesota: A. negundo, Box Elder; A. nigrum, Black Maple; A rubrum, Red Maple; A. saccharinum, Silver Maple; A. saccharum, Sugar Maple; A. spicatum, Mountain Maple; A. ginnala, Amur Maple and A. platanoides, Norway Maple. The latter two are not native but introductions that have naturalized.
Uses: Silver Maple wood is moderately hard and close grained and has been used in furniture, boxes, paneling, etc. The sap can also be used for Maple Syrup but the yield is low - only about 1/2 of that from the Sugar Maple, A. saccharum. Fernald (Ref. #6) reports that some of the early botanists such as Michaux and explorers such as John Richardson, believed the syrup from Silver Maple to be better - sweeter and whiter.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"