Small tree introduced to US in 1800s

Published 8:29 am Monday, December 11, 2017

By Emilie Justen

Minnesota Department of Agriculture

December’s Weed of the Month is a small tree called Amur maple (Acer ginnala). It is native to China and Japan and was introduced to North America in the 1800s as an ornamental plant. Though valued for its brilliant fall color, it has become invasive throughout the eastern and Midwestern states, including Minnesota.

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Amur maple is a deciduous large shrub or small tree that grows to 20 feet. The leaves are 3-lobed with toothed margins and turn a vibrant red in the fall. It produces abundant double-winged samaras typical of maple trees. The bark is smooth and grayish brown. The plants grow in single stem or multi-stemmed clusters and is found in open woodlots, forest edges, disturbed areas, roadsides and ornamental landscapes. Amur maple can grow in a wide range of soil types and will tolerate shade.

Amur maple spreads by seed in addition to ornamental plantings. Seed can be carried long distances by wind and water. Amur maple plants can alter habitats, invading prairies, grasslands, or open woodlands where it can add a shrub layer. Because of its prolific seed production, it can displace native shrubs, understory trees, and native herbaceous plants.

Amur maple is a Specially Regulated Noxious Weed in Minnesota and should only be planted in landscapes where the seedlings will be controlled by mowing or other means, and should be planted at least 100 yards from natural areas. Although landowners are ultimately not required to control or eradicate Amur maple on their properties, they are encouraged to manage Amur maple appropriately to prevent future spread of this species and degradation of native habitats.

Several management tactics are available for Amur maple. For all options, infestation sites will need to be monitored and treated repeatedly until the seedbanks are depleted. Stumps and sprouts that appear to have died can resprout after several years.

Should you decide to plant Amur maple on your property, please follow the label instructions by not planting Amur maple within 100 yards of any natural areas where seedlings would not be controlled.

There are a variety of native species that can be substituted for Amur maple that are not invasive and provide many ecological benefits to Minnesota landscapes. You can find these recommendations on the Minnesota Department of Natural Resources website.

Small infestations can be controlled manually by digging and removing the root crowns. Saplings are easily pulled by hand or controlled by mowing.

Prescribed burning can be an effective method of control on established populations. Make sure to contact the Minnesota DNR to learn more about control burning practices and regulations.

Infestations can be controlled by cutting and treating the stumps with herbicide or basal bark spray treatments. For specific herbicide recommendations, check with the University of Minnesota Extension, a local co-op, or certified landscape care expert.

The Weed of the Month is a series of articles about Minnesota noxious weeds. To learn more, go to the Minnesota Department of Agriculture’s website.