The Norway Maple

The Norway Maple (Acer platanoides) is one of the earliest trees to flower in the NE. It's clusters of chartreuse flowers signals the beginning of spring. Introduced to the US in 1756, it quickly became a popular street tree for its ability to tolerate adverse conditions. On the other hand, the native Sugar Maple is famously (among gardeners) unable to tolerate disturbance to roots, heat, and drought, associated with life in urban areas. Many other native trees like the American Elm, Ash, and American Chestnut were killed by diseases hitchhiking over on plant from Europe. To replace the rapidly dying canopy, trees like the Norway Maple were planted. The Norway Maple made itself at home in the NE and quickly began to spread outside of gardens and cities. However, at the time, much of the land was being farmed so its opportunity to invade forests was lessened because there were no forests to invade.

Norway Maple flowers

 Plains and elsewhere, Farmland was abandoned en masse and allowed to revert back to forest. In the past, Eastern Hemlock (Tsuga canadensis), Sugar Maple (Acer saccharum), and Red Oaks (Quercus rubra) would be the dominant species in a climax forest. However, the Norway Maple had many advantages. For example, its root system is thick and fibrous, allowing it to literally suck the life out of the soil, as anyone who has tried to grow a lawn under one of these trees can attest. In addition, any plants that managed to grab a foothold under the tree would be shaded out by the Norway maple's wide leaves. The fact that it is one of the earliest trees to leaf out also helps. Its ability to out compete many trees also allows it to suppress the understory. There is simply not much that can grow under a Norway maple. Interestingly, to me these characteristics would be a dealbreaker for an ornamental tree not to mention that it often girdles itself in cramped environments, that it, strangle itself to death with its roots, but I guess some people want a carefree tree.
 
Norway maples often establish pure stands, especially near areas disturbed by humans. In the more far flung areas, there are isolated specimens, but something has kept them from establishing themselves. Either they physically did not spread there or they may have already died out since their lifespans generally under 100 years as the secondary growth forest grows. Either way, it is considered an invasive species for its ability to displace native plants in disturbed sites.

I don't have anything against introduced species coexisting with native species but as some of the introduced species, like Norway Maples push other plants out, then they become a problem. Even in their native habitat, they do not form monocultures since there are diseases and other plants that keep them in check, which are not present in the US. These species should be dealt with accordingly, ideally by extirpation. However,  the attitudinal fix of education probably won't work, especially when the tree is mainly planted in urban areas where people can't see its effects. A technical fix would be creating a sterile variety that can;t reproduce. But there are certainly breeding populations out there already and those would need to be eliminated. The structural fix of banning the sale of them, which has been done in some states like Wisconsin and Illinois, where the invasion has been worse, but the sale of the Norway Maple in New York is still legal and only regulated in a way that intentional introduction into the wild is illegal. The Norway Maple is probably one of the oldest invasive species in the US, and like almost all the other ones, was introduced as a ornamental or agricultural plant with an intended use. The list of problems the cause goes on and on. It also goes to show that some actions intended to fix problems can create more problems than they are worth.