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Homeyer: Norway Maples

10/19/11 5:55PM By Henry Homeyer
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(Host) Commentator Henry Homeyer says that spending time removing invasive species from our woods and fields now, may pay off in brighter foliage later.

(Homeyer) The fall foliage season is one of my favorite times of the year. I love the reds, oranges and yellows of our native sugar maples. But there are a number of factors that can threaten these lovely trees including acid rain, insects, and competition from foreign invaders.

When I say "foreign invaders" I'm not talking about terrorists. I mean plants from other continents that can out-compete our maples. One of the most problematic of these is the Norway maple. Although it was introduced to the United States from Europe in the mid-1700's, one of the most commonly used varieties, Crimson King, comes from Belgium where it was first developed in 1937 and introduced here in 1945.

I'm sure you‘ve seen Crimson King: It's a big tree with dark purple leaves in the classic maple shape. It's common on lawns and along city streets, sometimes replacing the American elm that's been killed off by disease. It's a tough tree that will grow in sun or shade and in almost any kind of soil. Sugar maples don't thrive if their roots are compacted by pedestrians or cars, but Norway maples don't seem to mind. They produce huge numbers of seeds that can wash down hill and downstream to grow far from the mother tree.

According to one Vermont forester I talked to, if you love maple syrup and fall foliage you should get rid of Norway maples on your property. They can out-compete sugar maples and take over their habitat. Crimson King is a hybrid that rarely has offspring with purple leaves, so many people don't recognize their seedlings. They don't know that those nice young maples growing in their woods are Norway maples, not sugar maples.

But there's an easy way to identify a Norway maple: snap off a leaf and look at the attachment point. That leaf stem will ooze a white sap if it's a Norway maple, but not if it's a sugar maple or a red maple.

I'm a New Hampshire resident and I'm pleased to report that my state has declared the Norway maple an invasive species and banned the sale or transportation of them. Not so in Vermont. Norway maples are listed in Vermont as potentially invasive, even though most other states have banned them. In that same category - potentially invasive - Vermont includes burning bush and barberry, two other landscape plants that are taking over woodlands in some areas.

Gardening is largely over for the season, so I have time to take on other outdoor pursuits. I'll spend some time this fall cutting down or pulling out invasive plants on my property. I don't have any Norway maples, but I have plenty of invasive honeysuckle bushes and some barberry bushes that the birds have planted.

I'll get to work on those and hope my neighbors will take out a few invasives too.
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