Norway maple (Acer platanoides)

Invader Type: 

Control

Mechanical Control: 

Hand pull: Any time of year when the ground is soft, especially after a rain, hand pull small plants by the base of the stem. Be sure to pull up the entire root system. Hang from a branch to  prevent re-rooting. For larger plants, use a Weed Wrench™. Continue to monitor the area every year for new seedlings.

Cut stump: Cut plants back in the fall or winter. Wrap a few layers of burlap or thick plastic over the stump and tie tightly with twine or rope. Check covered stumps periodically and cut back any new growth.

 

Chemical Control: 

Cut stump: Cut the plant 4 inches above the ground. Use a drip bottle to apply a 18-21% glyphosate solution to the stump within one hour of cutting. This is best done in late summer through winter when plants are transporting resources to their root systems.

Low volume foliar spray:  This method is used for dense populations and best left to a contractor. In the fall, when native plants are losing their leaves, spray a 2% glyphosate solution on the entire leaf surface of the plant. In order to avoid drift to native plants, spray only on calm days.

 

Photos

Photos: 

Description

Identification: 

Norway maple is a deciduous tree which reaches 40 to 50 feet in height, but can grow up to 90 feet tall. The crown is oval to rounded with a central leader and heavy dense canopy.  The bark is gray and very smooth as a sapling, developing shallow and regular grooves with age.   The leaves are opposite, palmately lobed with 5 lobes and 7 points.  Leaves are about 6 inches wide and 4-5 inches long and dark green.  A milky substance exudes from the petiole when leaves are removed from twigs. 

Reproductive Strategy / Lifecycle: 

The yellowish-green flowers of Norway maple appear in stalked clusters in mid to late April as the leaves are expanding. They are insect pollinated. Fruits mature in late summer into wide-spreading wings that split down the middle. Large numbers of shade-tolerant seedlings are produced. Populations of these trees will also expand locally by vegetative reproduction. 

Dispersal: 

Seeds are wind dispersed in fall, providing a high likelihood of protection under winter snow – conditions usually sufficient for stratification as well as protection from extreme cold.

Habitat: 
Norway maple is tolerant of a wide variety of soil, moisture, and light conditions. It prefers full sun, and can withstand hot dry conditions. It is tolerant of ozone and sulfur dioxide air pollution and has adapted to extremes in soils. This tree can be found in early and late succession forests, forested wetlands, open disturbed areas, roadsides, vacant lots, yards, and gardens. It has been found in woodlands near cities, especially in the northeast. Norway maple can be locally dominant in forest stands, create dense shade, and displace native trees, shrubs, and herbs.
References: 

Photos: J. Randall; (c) S. Kuebbing; (c) J. Samanek State Phytosanitary Administration; (c) L. Mehrhoff University of Connecticut.

Threat

Ecological Threat: 
  • Unlike native tree species, Norway maple hosts very few native caterpillars, reducing an important food source for bird populations
  • Native mammals do not recognize Norway maple seeds as a food source, further reducing native tree populations.
  • Norway maple (Acer platanoides) provides breeding habitat for another highly invasive species, the Asian long horned beetle (Anoplophora glabripennis), an insect that threatens to significantly reduce North American hardwood forest stands. Research shows female beetles will live longer and  produce more fertile eggs on non-native Norway maples than on native red maples (Acer rubrum).