The sugar maple
Peter Duinker, Halifax Tree Project
2020-08-04
Nothing sounds sweeter to an Eastern Canadian than maple syrup. Indeed, Canada produces about 3/4 of all the maple syrup in the world, with Quebec producing about 90% of that. Ontario and New Brunswick have substantial shares in the remaining production. While it is possible to make maple syrup from other maple species, none can match the high sugar content of the sap of the sugar maple. It takes about 40 units of sugar-maple sap to make one unit of syrup! All of our commercial maple syrup and sugar products come from the sap of the sugar maple.
It would be impossible to grow up in a rural area of the Maritimes (and the southern portions of ON and QC) and not be aware of the sugar maple (Acer saccharum Marsh.). I got to know the species intimately as a pre-schooler by shinnying up some young specimens on the grounds of the Sharon Temple in Sharon, ON. The sugar maples I climbed there in the late 1950s were about 10-15 cm in diameter and perhaps 8-10 m tall. I revisited those trees in 2017, some sixty years later, and was pleased to see most of them still growing vigorously (see photo, right).
Some people think that the sugar-maple leaf is the leaf in the centre of Canada’s flag. Others have said that it’s probably more like a Norway-maple leaf. You be the judge - I’ve provided a photo of a leaf from both tree species in my back yard, plus an image of our flag. I prefer to think that the artist who designed the flag - George Stanley (with a minor modification by Jacques Saint-Cyr on the number of leaf points from 13 to 11) - was more motivated by an iconic native tree species.
There is also a popular misconception, I believe, among Canadians that the sugar maple is the arboreal emblem of Canada. According to the Government of Canada’s website, “Canada’s arboreal emblem is the generic maple species”, which is actually rather awkward because there is no such thing in nature. If it’s a “generic maple”, then it’s not a species but rather a genus (in this case, Acer). Ten maple species (of about 150 globally) grow naturally in Canada.
Anyway, back to sugar maple, also known as hard maple and rock maple because of the hardness, strength, and density of the wood. The wood is used for a wide range of specialty products including flooring, furniture, and various and sundry household items. I am very pleased when sugar maple shows up (unfortunately rarely) in my annual acquisition of commercial firewood because of its high heat content.
You will find precious few mature sugar maples in the streets of HRM. To my understanding, this is because nursery stock of cultivars that would consistently do well in the street environment was limited some decades ago. This, in turn, might have been the case because urban foresters and arborists were reluctant to plant sugar maples streetside on account of their poor performance. Many other tree species have, over the long term, proven most robust and resilient in the street environment, so why choose sugar maple? Moreover, decades ago, urban foresters had no hesitation to plant the street ecosystems full of non-native tree species - like the Norway maple! I encourage you to read that article if you haven’t already.
After this series on street-tree species is complete in October, we will be venturing into other urban-forest topics including how to identify one tree species from another. For now, I will indicate the main ways I tell sugar maple from two other common maples - the Norway and the red (red maple, Acer rubrum L., will be featured in an article in late August). The leaf margin of a red maple has numerous teeth, and those of Norway and sugar maples have a small number of prominent points. The bark of Norway maple is finely and regularly ridged, whereas the bark of sugar maple (and red maple, for that matter) is rough-textured with irregular ridges and plates. If you squeeze the petiole (leaf stalk) of a Norway maple, the liquid that emerges will be white; from a sugar maple it will be clear. Finally, the samara (the fruit containing the seeds; as children we called these helicopters) of the sugar maple has a relatively small angle between the two halves, while that of the Norway-maple samara is wide.
I’m glad that our HRM urban foresters have lately warmed up to the notion of putting more sugar maples into the mix of street-tree plantings each year. A popular cultivar is Green Mountain which seems to have good resilience in the street environment. My research assistants just completed a five-year remeasurement on the trees planted alongside HRM streets in 2015. Of the 18 species in that remeasurement, there were 102 sugar maples and only one had died. This was by far the highest survival rate of all the species measured. Way to go, sugar maple!
For a relatively healthy mature sugar maple in our streets, my favourite is the one on the north side of Allan St. just east of the intersection with Monastery Lane (6th tree from the fire hydrant). My own street - Lawrence - has a lovely young Green Mountain sugar maple that is the 8th tree in from Harvard on the north side.
Two more wonderful examples. On Cartaret St. at Oakland St. is a dying sugar maple that has been ravaged by a woodpecker - I’ve never seen such aggressive work by a woodpecker (probably a pileated woodpecker) in a city environment. The woodpecker is not killing the tree by doing this – that branch of the tree was already dead, and the woodpecker was just taking advantage of the softness of the decaying wood and the potential abundance of insects to eat.
Finally, there is a newly established grove of sugar maples in a grassy island at the intersection of Barrington St. and Cornwallis St. I have monitored this grove of healthy sugar maples since it was installed some years ago - the photos are from 2015 and 2020. I sincerely hope that the Cogswell District project does not implicate this small wooded patch of land, and if it does, I hope we can convince the city and the developers to remove these trees to another, more stable location. Removal will require specialized equipment, but it will be well worth the effort to save them.
