Acer platanoides Seeds | Norway Maple

Five-lobed green leaves and upright clusters of yellow-green flowers on a Norway maple — Norway Maple (*Acer platanoides*): Sapindaceae, native to Europe and western Asia, widely planted and widely naturalised.

LATIN NAME: Acer platanoides

COMMON NAME: Norway Maple

Plant Profile

Norway maple is the tree that made the northern street, and it is also the tree that taught North American foresters what a mistake a good street tree can be. It is large and broadly crowned, twenty to thirty metres in the open, with a straight grey trunk that stays clean to a good height. The leaves are five-lobed, broad and thin enough to move in wind, dark green above and paler beneath, turning clear yellow in autumn rather than the red of sugar maple. The flowers open with the leaves in early spring, in upright yellow-green clusters, and are a better nectar source than their colour suggests. Seed is a wide-winged samara, ripening in autumn and spinning as it falls. Everything about the tree says adaptable: it takes poor soil, air pollution, salt, hard pruning and shade, and it grows fast while doing so.

Science & Biotechnology

Acer platanoides is a diploid with 2n = 26, and it is one of the most thoroughly studied of the maples because it is both a model urban tree and a documented invader. The two facts are connected: shade tolerance, early leaf-out, rapid growth and heavy seed production let it establish under a closed native canopy in eastern North America, where it now displaces sugar maple and oak regeneration. Work on its litter and root exudates suggests allelopathic or at least inhibitory effects on understorey plants, though the mechanism is still argued. The petiole exudes a milky latex when broken, a reliable way to tell it from sugar maple at any season. Seed requires cold, moist stratification and is unusually tolerant of storage, and the samaras disperse on wind over considerable distances.

Uses & Benefits

As timber it is second-rate: pale, soft, fine-grained and not durable, used for turnery, pallets and firewood. As a street tree it has been first-rate for two centuries, and the purple-leaved forms, above all Crimson King, made it a fixture of parks and avenues. The shade is dense and the crown formal, and the tree will put up with pavement, dog urine and road salt. The drawbacks are now well known. The roots run shallow and lift paving, the seed germinates everywhere, and the shade is too deep for much to grow beneath. It produces abundant nectar in early spring, which matters for bees at a lean moment, and the buds feed squirrels in late winter. The sap is sweet but far less sugary than that of sugar maple and is not boiled commercially.

Growing from Seed

Sow fresh samaras in autumn, either directly outdoors or in a cold frame, and let winter do the work; stored seed needs three months of cold, moist stratification at about 4 degrees. Germination is epigeal and the seedlings are large and fast, so sow thinly and pot early. Use any reasonable compost, keep evenly moist, and give full light after germination. The first year’s growth can be forty centimetres, and the tree is ready to plant out at sixty to ninety centimetres. It transplants easily, even bare-root, which is another reason it became the standard street tree. Water for the first two summers and then leave it alone. If you garden where the species is invasive, cut the samaras before they ripen, or choose a seedless cultivar.

Our Take

A tough, fast shade tree with a serious invasive record in parts of North America. Check local guidance before planting it, and do not expect much to grow in its shadow.

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