Believe it or not, the trees in this photo are all Norway maples. You are likely familiar with the tree in its natural form which looks much like the sugar maple. Bred to grow in a columnar form, this Norway maple (Érable de Norvège, Acer platenoides) has been widely planted in areas of the city where the sidewalks are narrow and there is no or little garden space in front of houses and buildings. For obvious reasons, my children call this tree the Marge Simpson maple.
I remember when the trees in the photo were planted 17 years ago on la rue Roy. Local residents were sceptical of the spindly looking tree with the strange shape. We were also doubtful of the trees’ chances of survival in their cubic metre plots of earth in a narrow strip of sidewalk. But our doubts have been assuaged; those trees that survived the salt, the snow-clearing machinery and the late night partiers who occasionally try to swing from a branch are looking good. Lush and dark green in their eccentric forms, these columnar Norway maples provide shade, coolness and sculpture to streets that had never known trees.
And yet, this is the same tree that is considered an invasive species, one that should no longer be planted either by municipalities or by individuals. Why?It has to do with the Norway maple’s great reproductive capacity, the fact that it is not a native species, and that the tree creates too much shade — at least in a forest or a park. Being originally from Norway — although in North America since the 17th century — this maple isn’t well adapted to fostering the growth of understory plants — at least not on this continent. In our native sugar maple forest, on the other hand, many species of herbaceous (non-woody) plants thrive under the maples and their accompanying trees (see last week’s column on Mount Royal).
Thanks to the rich leaf compost of the sugar maple and the fact that the bright green leaves permit sufficient light to reach the forest floor, such plants as trilliums/les trilles (in the spring), wild carrot/carotte (in the summer) and asters and goldenrod /verge d’or (in the autumn) find the light and nutrients that they need.Under the Norway maple, however, both the quality of the leaf litter and of the light changes. In fact, the dark green — or dark crimson, in the case of the Crimson King variety — leaves permit little light to reach the forest floor. The result is that very little grows beneath the tree. If you have every walked under the canopy of the Norway maples in Parc La Fontaine, on the asphalt path that leads south towards École le Plateau, you will know what I mean.
Trouble is that once a Norway maple is planted or seeds itself in the sugar maple forest, it begins to dominate thanks to the fact that it produces more seed, more frequently than its North American cousin. This is a problem on the east face of Mount Royal in the section north of the George-Étienne Cartier monument and south of the Olmstead Road. At this time of year the leaves of the Norway maple stand out will from those of the sugar maple: they turn yellow rather than red or orange and many are also stained with a fungal black spot that doesn’t seem to affect the sugar maple.Is the solution to stop planting Norway maples altogether?
Lynda Génois, horticulture technician for the Arrondissement du Plateau Mont-Royal, says that her service continues to plant Norway maple though less than before. “We find the the trees in the pea family, such as the honey locust and Kentucky coffee tree, are more resistant to salt and insects than the Norway maple,” she says, adding that in her arrondissement there is no ban on planting the fast-growing Norway maple.On Mount Royal, however, no more Norway maple trees are planted and Les amis de la montagne have several projects underway to removed the Norway maple seedlings.
So, it would seem that as long as this tree is kept far from the sugar maple forest, it may continue to play its role as a tough and maleable — for shape and colour, that is — urban tree.If you are interested in learning more about a variety of city trees and how they ended up in their various streets, allies and parks, I would invite you to my tree walk this Saturday entitled: The Trees of St-Louis: From Square St-Louis to Marianne Street. Via the stories told by the trees, we will travel from the days when this land was farmland; from the period when the Square was a water reservoir; and from the time when the enormous St-Louis de France church dominated Roy Street.
WHEN: Saturday, September 27 at the west entrance of the gazebo (la vespasienne) at Square St-Louis
TIME: 10h to 12h
FEE: $10
REGISTER: 514-284-7384, bronwynchester@gmail.com
WEB: www.foretmontreal.com
4 comments
Yes!
Your informative and tremendously interesting articles on the trees of Montreal get the “BALLIN'” award.
A+
I second that! This past Sunday I wandered into the Morgan Arboretum from the organic farm I was visiting on chemin Senneville (West Island), and my experience was greatly enhanced even just by what I’ve learned so far from your articles and walks. One feels much more a part of a natural place when one knows something of its history and makeup.
Although I’d prefer favouring native maples in new plantings, we need to protect all the shade trees we have. I hate those silly trees the city has been planting – say, along Beaubien between St-Laurent and St-Denis after the road was rebuilt – are those pea family trees? They are spingly things that give no shade whatsoever, even after several years. Look like weeds.
Not only is the Norway maple a non-native species but, in true Canadian fashion, its leaf is what appears on our flag. Not the red maple, nor the silver, nor sugar, heck not even the mountain or the Manitoba maple. Nope, our flag is inspired by the Norway maple.