The Ontario Invasive Plant Council, in conjunction with the City of Toronto and York Region, has developed this very informative document about best management practices for Norway Maple.
The resource can be downloaded through their website at the following link: www.ontarioinvasiveplants.ca/invasive-plants/species/norway-maple/
“In recent years, awareness of its invasive potential has increased, and many municipalities and some nurseries no longer plant or sell Norway maple or some of its cultivars. However, there are several Norway maple cultivars still widely sold in nurseries due to their attractive appearance, urban tolerance, ease of production, low maintenance and relatively low cost. The ‘Crimson King’ cultivar has bright red foliage throughout the growing season, and ‘Emerald Queen’ has dark glossy-green leaves and yellow fall colors. Although beautiful, cultivar seedlings can spread into natural areas and become invasive, outcompeting native species and impacting wildlife. See page 5 to learn more about Norway maple cultivars. With its potential for being a serious invader, preventing this invasive maple species from entering and damaging natural areas is an important priority for land managers land use planning, and landscape design.”
“Norway maple can be highly invasive with a potentially profound impact on forested habitats throughout southern Ontario and eastern North America. Where it has spread from nearby urban seed sources, many ravines, parks and natural areas exhibit nearly pure stands of this species. Its adaptability, ability to cast dense shade, prolific seed production, lack of insect and disease pests and longer leaf lifespan have made it a formidable competitor over native species. It has many competitive advantages over native sugar maple, such as making more efficient use of light, water and nutrients…
Once Norway maple is well established in a forest, it forms a dense forest canopy that shades out most species on the forest floor and in the canopy. In mesic deciduous forests of eastern North America, native plant species primarily evolved under the canopy of sugar maple and other native maple and tree species, which allow more light to penetrate into the forest canopy. Few native species can survive the dense shade of Norway maple, which then inhibits the regeneration of other native tree, shrub, and herbaceous plant species. In addition, Norway maples grow faster than native maples and their dense, shallow root system makes it difficult for any plant species to grow in the understory