365 Urban Species. #297: Norway Maple

Photos by urbpan. Location: Harvard Street, Brookline.

Urban species #297: Norway maple Acer platanoides

The first people to plant Norway maple trees in North American cities must have found the project very satisfying. They grow quickly, and grow very straight, and have pleasing symmetrical crowns of shade-producing foliage. They handily endure the various hardships of urban life, and can be planted in the smallest square of soil in a sidewalk. Unfortunately, they have become invasive pests that threaten the forests surrounding the city. Many mixed hardwood forests in southern New England are becoming dominated by Norway maples, which grow much more closely to one another than native trees. They compete for soil area and sunlight, displacing forest herbs and wildflowers.

They are one of the few species of tree in the city that will plant themselves. Often they are found along fences and other hard-to-mow areas, squeezing into whatever space is available. Cutting them down often only encourages them to resprout (as is also the case with another troublesome city tree, Ailanthus altissima. I have found, managing some areas of a wildlife sanctuary, that repeated cutting eventually stresses the tree to death, whereupon it often sprouts turkey tail mushrooms. In past years I would feed the cut saplings to my captive deer, but this fall the Norway maples developed tar spot and anthracnose fungus, and their leaves were dry and unpalatable.

Norway maple looks similar to sugar maple, but can be told by its very smooth bark, very straight growth, and relatively larger leaves. The leaf stems of Norway maple ooze white latex sap when broken, which other maples do not. Norway maples stay green longer than native maples (unless they have succumbed to fungus) and in late fall turn yellow rather than red or orange. The wings most of our native maple samaras (fruits) are at an angle to one another, forming a U (see boxelder, for example), while Norway maple samara wings are flatter, forming a shallow V.


There are various cultivars of Norway maple, including strains with leaves that are purplish.

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