Xec: I agree completely and have been following the fate of Boston trees for 5 decades. The streets of Boston and beyond used to be covered in American Elms and and many Black Walnut trees. We all know what happed to those. Bugs and fungus killed them off and denuded many of Boston's residential neighborhoods, the ?Common, and certainly nearly all suburban main streets. Then was a time when Linden trees were the rage (the kind at the Christian Science Center). They could be trimmed and were very hearty against winters and salt and smelled great in the spring. But they gave off tons of sap (all over cars parked under them) and were prone to a terrible fungus. Then came the great London Plane Tree efforts (the kind that used to grow in Copley Square and along the street of Govt. Center). They had a short life due to mildew disease and also dropped a lot of messy leaves. Good-bye Plane trees. Then there was the Bradford Pear Tree phase, which were hearty and flowering, small and compact. But they were discovered to be invasive, non-native to NE, smelled poopy when blooming, cross-pollinated with other species, and an environmental problem. Good-bye pears. Then the Locust tree phase (as seen in Quincy Market). These grow very large, have small leaves that are more manageable to sweep up, and resist pollution. But they seem to be better suited for off-street planting where the branches can spread without having to be pruned back. And of course we can't forget the huge efforts made by Menino to plant street trees all over the city. I watched as openings were dug in all the sidewalks and many of the holes never got a tree. Sidewalks were often too narrow and trees robbed people of easy access. And then about half of the new trees that actually got planted were put in the shade of buildings and were not happy.
Narrow streets/sidewalks, snow, ice, salt, lack of water, impaction of the tiny earthen areas around roots, vandalism, trucks breaking branches, and leaf accumulation in gutters and sidewalks (causing a slipping hazard)...this and more have conspired to kill Boston's street trees before they get a chance to thrive. Oddly enough if you look at old pics of downtown, aside from the Common and Public Garden and parks around the city, there were very few, if any trees on the sidewalks and streets. (Whoever came up with the idea to put trees in front of Faneuil Hall didn't think ahead to when they would get large, block the view, and attract lots of pooping birds. Now they are all gone, cut down ignominiously through the years. And don't get me started with the use of rounded cobble stones as a great pavement for walkers!).
The idea for street/plaza trees, IMO, came about in part as a way of making large, open plazas more acceptable to the public, as many newer buildings manipulated the system to build tall by creating useless voids around their base (aside of lunch time crowds in good weather who hangs around these plazas, that often have no where nice to sit and have been marred by the grease used by skateboarders?) I'd rather have no trees along most streets and just have sidewalks that aren't tripping hazards. Beacon hill has done just fine. The Back Bay's residential streets are an exception. But not every section of commercial Boston can look like the Back Bay.