To finish this series on street trees, I’d like to mention some forces acting against street trees.
Street trees were a liability in early American cities. Benjamin Franklin’s fire insurance company in Philadelphia refused to cover houses with trees in front of them for a time. Having more burnable wood in front of your house was a problem before the city had an extensive plumbing system.
Departments of “transportation” (traffic) have long seen trees as either hazards or faraway scenery. The term of art is “the clear zone”. The width of the clear zone varies with design speed (the posted speed limit plus 5 MPH), and is meant to represent the distance a car flaying off the road would need to safely stop. Sometimes the clear zone runs beyond the right of way. Often the clear zone includes the sidewalk, because who walks anyway? As you might have guessed, the clear zone is meant to be clear of anything more threatening than grass. My own beloved Virginia DOT only recently quit referring to trees as “fixed and hazardous objects”.
Though they do have a point. Hitting a full grown tree with your car is a negative feeling.
The final liability to tree is their care. While the streets department of most cities may plant them, they probably leave tree maintenance to the adjacent landowner. The benefit obtains to them, after all. This is similar to the way sidewalks are maintained in most of the country, by the way.
The consequence of this is tat street trees become a homeowner expense without clear ownership. This usually means the trees are on their own, which gets back to their 85% mortality rate in the first fire years.
The forest of full grown trees is in peril as well. As trees age, they must be pruned and eventually removed, and replaced with something else, or not. Because the major costs of tree work are labor and mobilization (getting stuff tp you to do the work), the cost of removing a major branch is not much less than removing the whole tree. So why not just remove the tree? The expense of doing either is over a thousand dollars, a noticeable hit to most people’s cash flow.
After that, most property owners will be reluctant to plant anything at all for a year. They will be wary of replanting the same species of tree, with the fresh memory of how much trouble it was to remove. If a tree removes itself by falling onto a building after a heavy rain and windstorm, you can be damn sure the property owner will be unwilling to replace it with the same species. And so Oaks, Elms, and Plane Trees will often get replaced with Redbuds, Dogwoods and Crepe Myrtles.
Where I grew up, within a half block of a long gone trolley stop in Atlanta, I recall huge water oaks in the front and back yard and in the next door neighbor’s yard, giving dappled light to all at nearly every time of day. Water oaks are infamous for rotting form the inside, and my parents had them removed by the time I was in College. The Dogwood and Cherry grew faster in the backyard after that, but they will never reach that oaken canopy stature. I remember the songs of Robins and Starlings when I was a kid, but lately I am hearing ore woodpeckers. Not calling, but hammering their way into the old bark of an aging urban forest. The urbane forest of my youth is dying unless the city and property owners are willing to replace canopy trees, not just understory ornamentals
I write this bit on trees as a reaction to Jeff Speck’s spirited but vague chapter on trees, and then wrote your three posts of spirited, but vague things about trees. I am not an arborist, nor do I love the trees where I live now. Except for the Beech and the Lindens, Talk to your local tree service people about what they recommend. Many are in the service of ornament and traffic flow, but they know a hell of a lot more about the constraints of planing near curbs and houses in your area than the nurseries or me.