Trees and Shrubs of the Eloise Butler Wildflower Garden

Norway Maple is a medium size deciduous tree that grows to 40 to 70 feet high, up to 2 feet in diameter and has a dense rounded crown. The tree is considered invasive in Minnesota and in other states. However, it forms an excellent shape for a landscape tree but the easily germinated seeds will take over an area unless control measures are in place.

The national champion tree list no longer lists this species as of 2021.

The bark is gray or brown, somewhat corky and, with age, developing shallow furrowed long narrow ridges that sometimes interlace.

Twigs are stout, hairless, brown, with light colored lenticels and with large terminal buds that are green-purple with large scales. The visual effect is of a turban.

Leaves are opposite, simple, 5 to 7 palmate lobes with long pointed teeth on the lobes, wavy edges, and a little wider than long (up to 6 inches long and 7 inches wide). They are dark green above and paler below. The main veins radiate from the base and appear sunken on the surface of the leaf. The base is truncate or a bit heart-shaped. Leaf stalks are long and slender, exuding white milky sap when broken. Fall color is yellow.

Flowers: The tree can be monoecious, that is with separate male and female flowers or it is dioecious, with the unisexual flowers on different trees, which is the usual case. Male flowers (staminate) are produced in a 2 to 3 inch wide flat-topped cluster (a corymb) containing 10 to 30 flowers, each of which is quite small (no more than 1/3 inch across), greenish-yellow, with 5 sepals and eight stamens rising from a greenish central nectary disc. Each flower has a long smooth stalk. Female flowers (pistillate) appear in a similar arrangement and color but have sterile stamens (staminodes) and a pistil rising from a 2-carpel ovary with a pair of small wing-like structures. Flowers appear on the twigs of the prior years growth with the leaves. Fall color is yellow.

Seed: Female flowers mature to a pair of one-seeded samaras, each about 1-1/2 to 2 inches long, with a broad wing, paired at the top forming an angle that is just under 180 degrees, green initially and turning yellow to light brown. These mature in late summer to fall and germinate the following Spring; some persist into winter and when they drop from the tree, are wind dispersed.

 

Habitat: Norway Maple grows best in moist, adequately drained fertile soils. It grows less well on sandy soils, soils high in clay or high in lime. Seedlings are very shade tolerant and the entire tree is tolerant of dust and city smoke and haze.

Names: The genus, Acer, is the Latin word for 'maple.' The species name, platanoides, is derived from two words meaning 'like the Plane Tree' referring to a similarity to the leaf of the Plane Tree which is another European tree, not related to our species. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. Botanists have recently moved the maples into the Sapindaceae family from the older Aceraceae family.

Comparisons: The closest confusing tree would be the Sugar Maple, Acer saccharum, but there the buds are medium brown, the sap is clear, and the leaves are smaller and longer than wide. Norway Maple has the samaras paired at a much larger angle.