Norway Maple

Acer platanoides L.
Maple family (Aceraceae)

Origin: Europe and Western Asia

Background
Norway maple was introduced for use as an ornamental landscape plant.

Jan Samanek, State Phytosanitary Administration

Paul Wray, IA State Univ.

Distribution and Habitat
John Bartram of Philadelphia first introduced Norway maple from England to the U.S. in 1756 and soon began offering it for sale. It was planted on farms and in towns for its shade, hardiness and adaptability to adverse conditions. Norway maple has been reported to be invasive throughout the northeastern U.S. from Maine to Wisconsin, south to Tennessee and Virginia and also in the Pacific Northwest. Over time, as reforestation occurred across the Northeast, Norway maple joined native tree species as a component of eastern forest ecosystems. It also escaped from town plantings.

Ecological Threat
Norway maple forms monotypic populations by displacing native trees, shrubs, and herbaceous understory plants. Once established, it creates a canopy of dense shade that prevents regeneration of native seedlings. Although thought to have allelopathic properties (meaning that the plant releases toxins that inhibit or prevent the growth of other plants), research has not been able to confirm this.

Description and Biology

• Plant: broad deciduous tree up to 90 ft. in height with broadly-rounded crown; bark is smooth at first but becomes black, ridged and furrowed with age; milky sap.
• Leaves: paired, deciduous, dark green, palmate (like a hand), broader across than from base to tip, marginal teeth with long hair-like tips.
• Flowers, fruits and seeds: flowers in spring, bright yellow-green; fruits mature during summer into paired winged “samaras” joined broadly at nearly 180° angle; milky sap will ooze from cut veins or petiole.
• Spreads: to new areas by vegetative reproduction and seed.
• Look-alikes: other maples including sugar maple (Acer saccharum) and red maple (Acer rubrum). Distinguish Norway by milky white sap, broad leaves, hair-like leaf tips, samara wings straight out, yellow fall foliage.

Prevention and Control
Don’t plant Norway maple. Seedlings can be pulled by hand and small to large trees can be cut to the ground, repeating as necessary to control any re-growth from sprouts (see Control Options).

Native Alternatives
Native maples like sugar maple (Acer saccharum) and red maple (Acer rubrum) would be good substitutes for this invasive tree.