Norway Maple  

Behalf Of James Parton
Sent: Wednesday, January 23, 2008 1:02 AM
To: ENTSTrees
Subject: [ENTS] Re: Pittsburgh Cutting Trees


I don't think I have ever seen a Norway Maple around here in WNC. I
wonder if Will has. If their leaves are larger than our native Striped
Maple than they really are big.

Judging by the name I figured it was an invasive tree, like Ailanthus
Altissima ( Paradise Tree or Tree of Heaven ).

James P.

== 4 of 12 ==
Date: Tues, Jan 22 2008 10:58 am
From: Carolyn Summers

Hi James,

Good question. Norway maples were Frederick Law Olmsted's biggest, longest
lasting mistake. He designed Central Park in NYC back in the 1800s and for
reasons no one fully understands, he decided to plant gazillion Norway
maples instead of our own gorgeous sugar maples. (I like this story because
it makes folks feel better to realize that even the best, most famous
experts really blow it occasionally.) This is no mere aesthetic problem,
because 100 + years later, Norway maples have naturalized all over
metropolitan NY and are threatening New England and parts south.

So why is that a problem? Norway maples evolved in Norway, a land with
greatly reduced sun compared to the NYC latitiude. Thus they evolved to
leaf out extra early, with extra-large, thick leaves. They also retain
their leaves longer in the fall. They are also extremely prolific in terms
of seeds. They have no insect predators; our insects can't tolerate their
leaf chemistry. The net result is that they are quite literally
outcompeting sugar maples, oaks and many other native trees and taking over
whole forests. Nothing can grow underneath their dense dark shade. Spring
ephemerals on the native forest ground layer can bloom and set seed and
complete their entire life cycle in the time it takes most eastern deciduous
trees to fully leaf out. That can't happen under Norway maples. To add
insult to injury, scientists supect that Norway maples are allelopathic,
that is, their roots exude toxic chemicals into the soil to further reduce

The Nature Conservancy has mounted an effort to arrest the spread, but the
nurseries in NY still sell them! It drives me crazy. If you see one, kill
it before it spreads.

I have a series of photographs that I use in my presentations that show the
various stages of leaves opening in the spring and also fully leafed out
Norway maples invading leafless forests in spring and fall. The pictures
really tell the story.
Carolyn Summers
63 Ferndale Drive
Hastings-on-Hudson, NY 10706

> From: James Parton <>
> Reply-To: <>
> Date: Tue, 22 Jan 2008 10:14:50 -0800 (PST)
> To: ENTSTrees <>
> Subject: [ENTS] Re: Pittsburgh Cutting Trees
> Why Norway Maples?
> On Jan 11, 5:12 pm, Carolyn Summers <> wrote:
>> Weıve had this problem, or a similar one, with Con Edison being urged on by
>> the Public Service Commission. Trees next to utility wires are taken down
>> in advance of storms as a way of preventing power outages that go on for
>> days after storms. We actually had a tornado in Westchester 2 years ago and
>> I think thatıs when concerns mounted. Iım always happy to see Norway maples
>> cut down, but when they go after the old oaks...... My advice to Pittsburgh
>> is to try to stop it, but settle for a publicly funded independent arborist
>> who will represent homeowners and monitor the cityıs contractors. Thatıs
>> what we did and the outcome was not too bad.
>> --

== 6 of 12 ==
Date: Tues, Jan 22 2008 11:39 am
From: "William Morse"

I was in Narvik and Tromso, Norway a few years back, ~400 miles north
of the arctic circle, and the only deciduous tree I recognized on the
city streets was Acer platanoides. An amazingly hardy species in its
own right. Travis

== 7 of 12 ==
Date: Tues, Jan 22 2008 11:58 am
From: "Lee E. Frelich"


Norway maple is hardy when it comes to dealing with short cool summers (as
in Norway), but not cold winters (as in Minnesota). In southern MN, Norway
maple is a stunted tree with many frost cracks on its trunk, which
nevertheless still manages to invade native forests. I don't believe it can
survive in northern MN, with -40 winter temperatures, at least for now. In
southern MN, Even as a crooked, cracked, stunted tower of tattered rot, it
still shades out seedlings of other tree species, and its leaf litter
favors invasion of European earthworms (some species of which are
detritivores that consume dead leaf litter) that cause further damage to
the ecosystem.


== 10 of 12 ==
Date: Tues, Jan 22 2008 12:43 pm
From: "William Morse"

I was there in January and February and the temps were 40 to 60 below
zero and the maples were all 20-40 feet tall. A bit smaller than here
in the states, but I can't say that they were stunted. I don't
remember seeing any frost cracks either..... maybe a local adaptation.
Norway maples have a wide distribution and depending on the
evolutionary history of the stock, less cold hardy species may have
been the progeny of the trees mentioned in MN. I would guess that it
is genetic variation from warmer-evolved parent material that makes
them less suited to MN winters. It would be nice if less
adaptive/maladaptive traits could be introduced into weedy populations
and create a population bottleneck for invasives. Travis

== 11 of 12 ==
Date: Tues, Jan 22 2008 1:23 pm
From: "Lee E. Frelich"


You are right--our Norway maple in MN must have originated from populations
further south. It sure doesn't tolerate our winters in MN very well.

The short heights in Norway are probably more a function of short summers
than winter minimum temperature.


TOPIC: Pittsburgh Cutting Trees

== 1 of 6 ==
Date: Wed, Jan 23 2008 5:48 am
From: "Will Blozan"


Unfortunately, Norway maples are all too common here in WNC especially in
big cities like Asheville and Hendersonville. Fortunately, a wilt has been
ruthlessly ravaging them and gradually eliminating them from the landscape.
They can be invasive but not as much down here as I have seen around NYC or

The NC state record is on Montford Avenue in AVL and is actually pretty
impressive. One of my clients had one with a crown spread in one direction
of 92' but it think verticillium wilt has gotten to it now.

I won't miss them.