Amur Maple is an introduced and invasive small tree, reaching to 20+ feet in height, typically on multiple stems and with a rounded crown about as wide as the tree is tall. Most grown as ornamentals remain shrub size.
The bark is smooth, grayish brown with darker striation furrows.
Twigs are slender, without hair, reddish brown with light colored lenticels. The buds are short and reddish brown, leaf scars are raised.
The leaves are opposite, simple, longer than wide, 2 to 4 inches long, 3 lobed with the middle lobe much longer that the two laterals. The edges of the lobes have some irregular teeth - double serrate. The leaf shape can be quite variable. Leaves in summer are bright green above, paler beneath, and a bright red in fall, although some specimens may be yellow in the Fall.
The inflorescence is a long-stalked cluster of long-stemmed fragrant flowers, the cluster erect at first, becoming pendulous as the samaras develop.
The flowers are bisexual, unlike many of our native maples. These are a pale yellowish-green in color. They appear with the leaves. The flower perianth is hemispheric in shape with 5 greenish-white overlapping calyx lobes, 8 stamens, exserted, with yellow anthers, and a 2-carpel ovary. Petals inconspicuous or absent.
Fruit: Fertile flowers produce paired samaras, about 3/4 to 1 inch long with the pair hanging from their common stalk at a very close angle. These are green initially becoming brown to dark brown at maturity after going through a red phase. Fruit ripens in fall and persists on the tree, frequently over-winter.
Habitat: This is a hardy species which can grow in full sun or partial shade, prefers moist well-drained soils but also handles dryness and alkaline soil. While the plant can spread via suckering, it spreads mostly by re-seeding.
Names: The genus, Acer, is the Latin word for 'maple'. The species name, ginnala is from the language of the trees native area - eastern Asia, China and Japan. The author name for the plant classification - ‘Maxim.’ refers to Karl Maximovich, (1827-1891) Russian botanist who extensively studied and wrote about the flora of the far east. Botanists have recently moved the maples into the Sapindaceae family from the older Aceraceae family.
Comparisons: The simple 3-lobed leaf is, with the exception of the Box Elder, Acer negundo L., a distinguishing characteristic of this species, but the Box Elder is a much larger tree. The closely paired samaras are also distinctive plus the brilliant red fall color.
Above: The leaves are basically 3-lobed with the terminal lobe much longer than the laterals. Dark green during summer they turn a brilliant red in Fall although some trees may produce yellow Fall leaves.
Below: The clusters of flowers develop along the twig on long stalks and become pendulous as the flowers mature to samaras.
Below: The individual flowers are small with 8 exserted stamens.
Below: The development of the seeds: The paired samaras are green at first, then turning a colorful reddish-pink by early summer and finally brown in the fall. 5th photo shows the small size of the samaras.
Below: 1st photo - bark is fairly smooth, grayish brown. 2nd photo - Twigs are reddish-brown with lenticels. Buds are short - same color.
Below: Originally planted in a long line as a landscape edge, these mature trees produce an abundance of new seedlings as the ground around this groups is red with the fall color of newer plants.
Below: Leaf comparison of common maples. Images not to scale.
Amur Maple has become naturalized in small number of counties in Minnesota and in states of the U.S. generally east of Minnesota and Iowa and North of a line from Kentucky to New Jersey. In Canada it is known in Manitoba, Saskatchewan, Ontario and New Brunswick. While the DNR has not listed it in Hennepin County, there are planted areas of it along highway right of ways. The plant is native to central and northern China and Japan. It was first imported in 1860 and it is still sold as an ornamental and shelterbelt plant. It re-sprouts easily from cut stumps and survives burning. Cut trunks should be treated with glyphosate or triclopyr to control it. Some states (such as Wisconsin) still do not list it as invasive, but Minnesota and many eastern states do, particularly in New England.
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"