Homeyer: Norway Maples

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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.

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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