According to observations of naturalists and beekeepers.
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200 kilograms per ha
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Norway maple is native to continental Europe and western Asia. It was introduced to the United States in the mid- to late 1700s in eastern Pennsylvania. A current, accurate description of Norway maple distribution in North America is problematic. It is widely planted throughout much of North America, especially along urban streets and in yards. In many areas, it escapes into the surrounding forest and woodlands, where it may become invasive. Precise distribution information for Norway maple is lacking.
Based on floras and other literature, herbarium samples, and confirmed observations, Norway maple can potentially be found in North America, growing outside cultivation, in the following areas: from New Brunswick and Cape Breton Island west to Minnesota and south to Tennessee and North Carolina. In the West, it is found in British Columbia, Washington, Idaho, and western Montana.
Norway maple is a nonnative tree, usually 40 to 98 feet (12-30 m) in height, with widely spreading, ascending branches. In Europe, Norway maple trees typically grow to a maximum diameter at breast height of 76 inches (190 cm) and live to 150 years. Bark on older trees becomes furrowed.
Flower: Regular (actinomorphic), yellowish-green, approx. 10 mm (0.4 in.) across. Sepals 5, free, triangular, alternating with petals. Petals 5, free, elliptic. Flowers bi- or unisexual. Receptacle nectar-secreting. Stamens 8. Pistil formed from 2 fused carpels. Inflorescence an approx. 20-flowered corymb.
Leaves: Opposite, lacking stipules. Blade palmately lobed with 5 to 7 lobes. Points of lobes long-tapered. Stalk approx. 10 cm (4 in.) long, containing latex. Autumn color varies from deep scarlet to orange and yellow.
Fruits of Norway maple are 2-winged samaras and each half of the fruit is typically 1.4 to 2.2 inches (3.5-5.5 cm) long.
Reproductive buds are formed during summer, overwinter, and open in spring when triggered by warm temperatures. Flowering dates vary geographically, ranging from late April to early June in eastern North America.