Soil compaction is a very big deal, which is why pedestrians who stray off paths are a real threat to the old trees in Boston Common and the Public Garden. A cherry picker used for pruning can do more harm than good if it runs over the roots of an old tree. A layer of plywood or mulch spread around the root zone can reduce root death from heavy equipment. Such replacement trees are frequently sited on the sunny south side of grizzled veterans, just outside the canopy so they can grow straight and tall. The typical example would be taking a native canoe birch or European birch and putting them in a lawn in dry soil.
Arborists also can help identify attacking organisms.
Everyone wants screens. But the tall canopy trees don't provide privacy because the canopy is up in the air, yet they shade out the shrubs and smaller trees that are screens. Especially Norway maples. A big percentage of new plants perish because they're in too dense shade and competition.'' Because many people view trees as a kind of pet, said Tobin, ''the biggest challenge I have is talking people into taking down trees. I was afraid one was going to go through their house.