Mountain Maple is a shrub-like tree that will grow to no more than 25 feet, it grows in moist acidic soil as an understory tree.
The flowers, appearing in mid to late May, after the leaves unfold, are greenish yellow and clustered on a narrow 3 to 6 inch high erect long-stalked flower stem (a raceme). This upright spike like flower structure led to the species name spicatum. This species is monoecious, that is, the male and female flowers are on separate racemes.
Twigs are yellow-green initially in summer, reddish in winter and spring and have fine hair. The buds have two easily seen outer scales.
Bark is thin, greenish on young stems becoming gray to grayish brown on thicker stems with a warty appearance, but without the greenish-white stripes of Striped Maple, A. pensylvanicum.
Leaves: The typically 3-lobed maple-like leaves are opposite, 3 to 4 inches long and with somewhat coarse teeth (unlike A. pensylvanicum which has fine sharp teeth) and with sharp points to the 3 broadly v-shaped lobes. The delicate veining gives a quilted appearance on the upper surface.
The fruit is a paired winged seed (a samara) about 8 mm high, where the paired seeds are at less than right angles to each other.
Habitat: Mountain Maple occurs in the understory of hardwood forests where the soil is somewhat rich, moist to mesic and the sunlight is dappled until full leaf-out of the canopy trees.
Names: The genus, Acer, is the Latin word for 'maple'. The species spicatum, means 'spike bearing' and in this case refers to the upright flower panicle. The author name for the plant classification - ‘Lam.’ is for Jean-Baptiste Lamarck (1744-1829), French naturalist, who published on botany and zoology and is known for his theory of the inheritance of acquired characteristics. In the 19th Century ths species was called Acer montanum. Botanists have recently move the maples into the Sapindaceae family from the older Aceraceae family.
Comparisons: The most similar species is Striped Maple, Acer pensylvanicum, which has striped bark, the flower racemes are nodding rather than erect and the leaves have finer teeth. Also, Striped Maple is dioecious - separate male and female flowers on separate plants.
Above: An old Mountain Maple in Eloise Butler. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - The spike-like long-stalked flower cluster. 2nd photo - The leaf is in the typical maple style with 3 (usually) broad pointed lobes with course teeth. 3rd photo - Bark on older stems has a warty look.
Below: 1st photo - Flower raceme developing. 2nd photo - Twigs are reddish in winter and spring, buds have 2 conspicuous scales.
Below: 1st photo - Male flowers of the Mountain Maple. 2nd photo - Female flowers.
Below: The samara of Mountain Maple is short - about 8mm high with an angle less than 90 between the pair.
Below: Flower racemes are typically found in groups toward the end of the branches. New twigs are greenish initially, turning reddish in summer.
Below: A leaf comparison of the common maples. Images not to scale.
Notes: Eloise Butler first planted Mountain Maple in the Garden on May 28, 1909 with plants obtained from the Park Board Nursery. This plant was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. Gardener Cary George planted it in 1994. The Garden hosts a large specimen near Guide Station 12 that is listed as a Minneapolis Heritage Tree. The tree is native to counties in the NE Quadrant of Minnesota and to the four counties of the SE Corner. In North America it ranges from Minnesota and Iowa eastward to the coast, down as far as Georgia and Mississippi. In Canada it is found from Saskatchewan eastward to the Atlantic.
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.
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"