Acer platanoides, commonly known as the Norway maple, is a species of maple native to eastern and central Europe and western Asia, from Spain east to Russia, north to southern Scandinavia and southeast to northern Iran. It was introduced to North America in the mid-1700s as a shade tree.

thumb|Flower, close-up

The flowers are in corymbs of 15–30 together, yellow to yellow-green with five sepals and five petals long; flowering occurs in early spring before the new leaves emerge. The fruit is a double samara with two winged seeds. the seeds are disc-shaped, strongly flattened, across and thick. The wings are long, widely spread, approaching a 180° angle. It typically produces a large quantity of viable seeds.

Under ideal conditions in its native range, Norway maple may live up to 250 years, but often has a much shorter life expectancy; in North America, for example, sometimes only 60 years. Especially when used on streets, it can have insufficient space for its root network and is prone to the roots wrapping around themselves, girdling and killing the tree. In addition, their roots tend to be quite shallow and thereby they easily out-compete nearby plants for nutrient uptake. Norway maples often cause significant damage and cleanup costs for municipalities and homeowners when branches break off in storms as they do not have strong wood.

Classification and identification

thumb|Tree in flower

thumb|Bark

The Norway maple is a member (and is the type species) of the section Platanoidea Pax, characterised by flattened, disc-shaped seeds and the shoots and leaves containing milky sap. Other related species in this section include Acer campestre (field maple), Acer cappadocicum (Cappadocian maple), Acer lobelii (Lobel's maple), and Acer truncatum (Shandong maple). From the field maple, the Norway maple is distinguished by its larger leaves with pointed, not blunt, lobes, and from the other species by the presence of one or more teeth on all of the lobes. The tips of the points on Norway maple leaves reduce to a fine "hair", while the tips of the points on sugar maple leaves are, on close inspection, rounded. On mature trees, sugar maple bark is more shaggy, while Norway maple bark has small, often criss-crossing grooves. While the shape and angle of leaf lobes vary somewhat within all maple species, the leaf lobes of Norway maple tend to have a more triangular (acuminate) shape, in contrast to the more finely toothed lobes of sugar maples, that narrow towards the base.

The fruits of Norway maple are paired samaras with widely diverging wings, distinguishing them from those of sycamore, Acer pseudoplatanus, which are at 90 degrees to each other. Norway maple sits ambiguously between hard and soft maple with a Janka hardness of . The wood is rated as non-durable to perishable in regard to decay resistance. In Europe, it is used for furniture, flooring and musical instruments, especially for violins.

Norway maple has been widely taken into cultivation in other areas, including western Europe northwest of its native range. It grows north of the Arctic Circle at Tromsø, Norway. In North America, it is planted as a street and shade tree as far north as Anchorage, Alaska. In Ontario, it is common in cultivation north to Sault Ste. Marie and Sudbury; although not considered reliably hardy northward, it has been established at Kapuskasing and Iroquois Falls, and even at Moose Factory. It is most recommended in USDA Hardiness Zones 4 to 7 but will grow in warmer zones (at least up to Zone 10) where summer heat is moderate, as along the Pacific coast south to the Los Angeles Basin. They tend to prefer wetter Oceanic climates. During the 1950s–60s it became popular as a street tree due to the large-scale loss of American elms from Dutch elm disease.

It is favored due to its tall trunk and tolerance of poor, compacted soils and urban pollution, conditions in which the sugar maple has difficulty. It has become a popular species for bonsai in Europe, and is used for medium to large bonsai sizes and a multitude of styles. Norway maples are not typically cultivated for maple syrup production due to the lower sugar content of the sap compared to sugar maple.

Cultivars

Many cultivars have been selected for distinctive leaf shapes or colorations, such as the dark purple of 'Crimson King' and 'Schwedleri', the variegated leaves of 'Drummondii', the light green of 'Emerald Queen', and the deeply divided, feathery leaves of 'Dissectum' and 'Lorbergii'. The purple-foliage cultivars have orange to red autumn colour. 'Columnare' is selected for its narrow upright growth. The cultivars 'Crimson King' and 'Prigold' (Princeton Gold) have gained the Royal Horticultural Society's Award of Garden Merit.

As an invasive species in North America

thumb|Feral Norway maple in Philadelphia.

The Norway maple was introduced to northeastern North America between 1750 and 1760 as an ornamental shade tree. It was brought to the Pacific Northwest in the 1870s. Today, Norway maples tend to be most common in the Pacific Northwest, in southern Ontario, and along the Kennebec river in southern Maine. The roots of Norway maples grow very close to the ground surface, starving other plants of moisture. For example, lawn grass (and even weeds) will usually not grow well beneath a Norway maple, but English ivy, with its minimal rooting needs, may thrive. In addition, the dense canopy of Norway maples can inhibit understory growth. Some have suggested Norway maples may also release chemicals to discourage undergrowth, although this claim is controversial. As a result of these characteristics, it is considered invasive in some states, and has been banned for sale in New Hampshire and Massachusetts. The state of New York has classified it as an invasive plant species. Despite these steps, the species is still available and widely used for urban plantings in many areas.

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File:Acer platanoides fruit kz.jpg|Fruit (samara): note the flat seed capsule and the angle of the "wings"

File:2014-10-30 10 39 54 Norway Maple foliage during autumn on Durham Avenue in Ewing, New Jersey.JPG|Typical yellow fall foliage

File:2014-10-30 09 32 43 Norway Maple foliage during autumn in Ewing, New Jersey.JPG|Atypical orange-red fall colour

File:Acer Platanoides 'schwedleri' leaf.jpg|Purple leaves of cultivar 'Schwedleri'

File:Acer platanoides twig and buds.jpg|Twig and buds

File:Knop van een esdoorn (Acer platanoides). 03-04-2023 (d.j.b.).jpg|Leaf bud.

Uitlopende knoppen van een esdoorn (Acer platanoides). 12-04-2026 (d.j.b.).jpg|Red-tipped buds of a Acer platanoides.

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Natural enemies

The larvae of a number of species of Lepidoptera feed on Norway maple foliage. Ectoedemia sericopeza, the Norway maple seedminer, is a moth of the family Nepticulidae. The larvae emerge from eggs laid on the samara and tunnel to the seeds. Norway maple is generally free of serious diseases, though can be attacked by the powdery mildew Uncinula bicornis, and verticillium wilt disease caused by Verticillium spp. "Tar spots" caused by Rhytisma acerinum infection are common but largely harmless. Aceria pseudoplatani is an acarine mite that causes a 'felt gall', found on the underside of leaves of both sycamore maple (Acer pseudoplatanus) and Norway maples.

References

  • Acer platanoides - information, genetic conservation units and related resources. European Forest Genetic Resources Programme (EUFORGEN)
  • Portrait of the Earth: Acer platanoides (Norway maple) — with winter images.