A Norway maple has three effective ways of destroying your lawn: dense summer shade, a smothering blanket of fall leaves, and a choking network of surface roots. There are mosses that will survive this onslaught, so treasure them. The prolific Norway seedlings also wreck havoc in the yard and surrounding garden.

No one doubts that Norway maples are beautiful: delicate lime-green flowers in spring, handsome leaves in summer, butter yellow, or sometimes red or orange in fall, graceful branches and trunks for the winter. The Norway maples hold their leaves longer in the fall than our native maples, providing late-season yellow accents for bare tree branches and winter evergreens. (FYI: Order of leaf turning: sugars, reds, Norway, silvers, then Japanese)

Norway maples aren’t so bad in Norway because it’s too cold for them in most of the country but they have become one of the most widespread trees in Europe, as well as being a major pest in North America. Since the way we nurture our lawns in the USA tends to be worse for the environment than Norways are for our lawns (see Issue 60), Norways wouldn’t be so bad except for their winged seeds (called “samaras”) that float off into our woodlands and wreck havoc there. What kills your lawn is also doing in our treasured woodland wildflowers.

Norways were introduced to North America in the late 1700’s. George Washington is said to have bought two from a Philadelphia importer. They became widespread around World War II when many were planted to replace elms stricken by the Dutch Elm disease. It seemed like a good idea at the time because Norways are one of the faster growing hardwoods that do well as street trees (handle pollution, live a long time, have strong branches). The problems didn’t show up until decades later when the mature trees and their grown-up, escaped decedents proved themselves to be lawn and forest killers.

So many, many Norway maples were planted along streets and in yards. Years later, the average home owner sees the trees gracing the neighbor’s yard and thinks: “nice tree, but why don’t they take better care of their lawn? They should put lime on the moss and re-seed under the tree.” The same person goes hiking in the woods, and wonders about the lack of wildflowers. The Norway maple’s culpability only becomes clear once it’s been pointed out.

Recently, a reader wondered why garden and landscaping professionals continue to recommend environmentally-unsafe plants like Norway maples. Equally intriguing is: why do homeowners buy them? Of course, every person acts for his or her own complicated set of reasons. But there are some identifiable trends. In this area, I suspect ignorance is a big one.

Plant nurseries and landscapers are no different than other retailers: their first concern is to make a living; not save the planet. They stock what they think people will buy. And they have to consider price. Fast growing, hardy plants are easiest to mass produce, cheapest to sell, and have the fewest returns and complaints. However, if they’re aliens, they also have the best chance of overwhelming the more delicate local flora.

The plant retailers know that most homeowners aren’t expert horticulturists and are more comfortable in choosing already familiar plants. Just think of the overuse of Impatiens. Since baby trees are relatively expensive long-term investments, people are even more likely to want to stick to the “tried and true”. So, popularity begets popularity, regardless of actual wisdom. This tends most pronounced with trees because the problems often don’t show up for 20 to 50 years. Sort of like smoking.

What we need to do is to demonstrate to our local retailers ever chance we get that we want sustainable agriculture and are willing to pay for it. That means buying the organic, local-grown produce in the store and farmers’ market, and planting non-invasive, low-chemical and water using, wildlife-nurturing plants in the garden.

So how do you tell the Norways from our lovely native sugar, red and silver maples? This is tougher than you’d think because maples interbreed and “cross-dress”. For example, red maples are supposed to have red stems but sometimes so do Norways, sugars and sycamore maples. See Issue 134 (coming October 17, 2004).