When is a beloved maple tree not a beloved maple tree? When it’s not a native species. Of eight species of maple growing in Ontario, one has caught the ire of conservationists, and over the last decade or so quite lot of effort has been made to get rid it. The dark one in question is the Norway maple.
We all know and love the sugar maple, the one that gives us sap in the spring and glorious colour in the fall. Sugar maple has also been called hard maple or rock maple, due its fine quality of wood when used for furniture making. This one is found all through the Great Lakes-St. Lawrence region, and is one of the commonest tree species to be found in a dry hardwood forest.
There are other maples, of course, ones that grow and thrive almost in obscurity when compared to their favoured cousin. Wet habitats are home to the red maple, also called soft maple due to its wood being of less dense construction than the dry land sugar maple. All the cells in a red maple are a bit bigger to accommodate the water, and the result is less density and therefore less value as a wood for furniture. Soft maple is often used as firewood.
Growing beside the red maple is another, called silver maple, a species which can also tolerate growing in very wet places. In the good old days one could tell them apart by their leaf shape, with silver maple having very deep cut lobes compared to the blockier red maple shape. However, with the application of DNA sequencing, it has been revealed that red and silver are hybridizing and the resultant offspring are now referred to as Freeman maple.
Now, about that Norway maple; an interesting history is to be considered here. As the name indicates, it came from afar, being deliberately introduced to Ontario in 1756 as an ornamental tree for estates. It grew fast and lush and sometimes had an eye-catching purple colour to the leaves (a variety that we now refer to as Crimson King). During the 1700s and 1800s it remained just that, a novelty species that enhanced lawn borders.
Now we get to the problem: Norway maple do let anything else grow under them, caused both by heavy shade and a root system that is very near the surface and robs any moisture from the soil.
In the late 1900s a disease killed off the white elm, a stately tree that lined roadsides both in town and in the country. With the demise of the elm a replacement tree was sought to populate our parks and lanes, and the sturdy Norway maple was chosen. I have no idea why a nursery stock species was chosen over the freely available sugar maple, but such is history.
Now we get to the problem: Norway maple do let anything else grow under them, caused both by heavy shade and a root system that is very near the surface and robs any moisture from the soil. Also, Norway maple produce a copious amount of seeds, called samaras (but we know them better as “keys”). The nearby sugar maples were not directly affected, but any seeds that they could distribute fell under the dominant Norway maples and never amounted to a new population.
As the old sugar maples died off, the Norway maple became the dominant tree species as it didn’t allow anything else to survive. Now, in the middle of a recreational park, a few big Norway maples are not a problem (other than the turf manager can’t get grass to grow under them). But when these trees were planted near natural woodlots, we now see the situation becoming a bit tense, as the natural ecosystem of that woodlot has been compromised.
If you lack a tree field guide and are wondering what the leaf of Norway maple looks like, pull out your wallet. Gloriously displayed on our $5, $10 and $20 bills is the almost circular leaf of a Norway maple. Go figure. Perhaps designed by an urban-based graphic artist that took a look at the trees in a nearby park over lunch breaks.
Our much loved sugar maple was even overlooked when the new Canadian flag was designed. Rather than portray a real maple leaf, a ‘designed by committee’ leaf was assembled to represent our country.
Next time you take a walk along a woodland trail, take time to not just look, but really see the different trees that make up a forest.
David J. Hawke is the Stewardship Program Manager at The Couchiching Conservancy, a non-profit land trust dedicated to protecting the special natural places throughout the region.