Since autumn and the inevitable falling of leaves is upon us, a great opportunity presents itself in disposing of a major infestation of non-native, exotic invasives. Usually I'm not so empassioned about gardening or plant wildlife in general, but with this topic I make an exception.
I am talking about the Norway maple, acer platanoides. Usually it is extremely difficult to remove this import from Europe and Asia. In fact, many nurseries still sell these trees, a practice which should be outright banned in all states, punishable by severe fines. The major problem with destroying any maple one finds is that native maples, especially sugar maples, could easy be mistaken for the Norway.
The good news is there are several ways to tell the two apart. One is the Norway's dense growth in extremely shady areas. Norways also excrete a miky sap when a leaf stem is torn off the branch, whereas a sugar maple's sap is clear.
However, the easiest way to tell the two apart is in the fall, when the leaves change color. The native sugar maple will have at least some tinge of red in their leaves. Usually they are all-red, but may contain some flecks of gold or brown. The non-native norway maple leaf will be completely golden-yellow or brown, and their leaves usually fall several weeks after sugar maples are done with their leaves. If you see an all-yellow maple tree in the woods late in the plumage season, it's almost certainly a Norway maple and should be destroyed. If it cannot be immediately destroyed then make a mark on the trunk (ie hatchet chop, lean a rock on the side, etc.) so it can be dealt with later.
Why am I so emphatic about destroying this tree? Because it is an "exotic invasive", meaning it is not only alien to our woodlands, but it ultimately out-competes native trees and undergrowth, destroying the bio-diversity of our woodlands and the ability of native wildlife to exist in those areas. The Norway maple produces enormous clumps of leaves, shading everything underneath them with an intolerable amount of darkness, something native plants cannot compete against. Berry bushes that would've supported native wildlife are stifled, since they never had the oppotunity to evolve and compete with such competition. The Norway also grows faster than nearly any other deciduous tree in North America; many have been reported to grow 4 FEET per year. The Norway also keeps its leaves longer than native plants; it is almost always the first tree to sprout in spring, and the last to lose its leaves in autumn. To add the ultimate insult to injury, the Norway maple excretes a mild but toxic substance into the soil around its roots, adding the finishing touch in preventing any other plant, other Norways excluded, from surviving underneath its dense canopy. It also seeds profusely; a single tree can spread thousands of seeds and seedlings across the landscape every year. Since the seedlings can tolerate dense shade, they grow quickly under any tree canopy. The Norway's sugar content does not even exist; it produces a milky sap that is un-suitable for sugar production, thus making it a direct threat to the American maple syrup industry.
The only sure way to remove a maple tree is to saw at the base, then "paint" the trunk base with a strong application of herblicide. However, too much to the surrounding area may damage other nearby plants. Without the herbicide application, the trunk will sprout dozens of new shoots. Within a year these shoots could easily reach 3 feet tall or more. Even lone trees, miles from any forest can pose a threat; a bird could digest the seed and carry it hundreds of miles on a migratory route, so removing as many as possible is helpful. Even without wildlife assistance the seeds are designed to float on the wind like a tiny sailboard; the seed could ultimately land several hundred feet from its original mother tree.
If a norway maple is being kept for shade or fall color, there are many, MANY native alternatives to growing this exotic, un-American tree. The tulip, or yellow poplar is a fast grower, and can provide equivalent shade and color conditions as the norway, but there are many other planting alternatives, including a native sugar maple.
This tree is a very significant danger in the northeast US and Canada. It is akin to brambles in the pacific nothwest, or kudzu in the deep south. Without assistance these trees will continue to spread and slowly wipe out wildlife and especially bio-diversity in our forests.