Species sugar maple (Acer saccharum) is a huge part of the regional forest composition here in western MA. At this very moment it is also a big part of our regional economy…the maple syrup production season is upon us. But you will not see these contributing to our ‘sense of place’ along any urban street. As one website describes it, “Sensitivity to compaction, heat, drought and road salt limit usage of Sugar Maple for urban street plantings…”
Your town may have a list of approved street trees that are “adaptable to urban conditions…handles our heat well. “ Or list a species that should be chosen because it “tolerates extremes of soil, heat and pollution; is very adaptable to soils and tolerant of salt, drought, and soil compaction; is tolerant of adverse environmental conditions.”
There are other reasons for selecting street trees…so they won’t interfere with utility lines or break up the sidewalks or drop messy twigs or fruit, or have an unpredictable branching habit that might not match one tree to the next along the street. But the one desirable characteristic common to all the lists on my internet search is the ability to tough it out in bad air, bad soil, excessive heat, and salt-contaminated water (at least in regions with winter conditions).
Such street tree lists often include a native genus, but the highway departments and homeowners are not just advised, but are required, to “Select resistant cultivars, tolerant of drought, salt, air pollution.” (As an aside, if you care about “reading the landscape,” the species list often becomes a roster of plants from other continents that, if planted along your street, would cause you to wonder where in the world you were standing.)
Here’s what I would like to know: why do we want urban plants that do not give us fair warning that environmental conditions are becoming bad for the health of living beings? Why do we want plants that show no sign that conditions are not suitable for habitation? Is it a good idea that, similar to Acer saccharum ‘Green Mountain’ and ‘Legacy’ with “thicker, waxier leaves, better to withstand heat and drought”, our lungs, skin, mucous membranes, and eyes might have to adapt to these conditions? Is it a good idea that specialized trees can thrive in these intolerable habitats, but we might get sick.
I can’t speak for everyone, but personally, I would like to see trees dying when the air and water are bad…as a clue that we should do something about the conditions.
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