New research is starting to indicate overpruning is bad, although the jury is still out on that. There's a balance, there really is. In all, there were 12,768 street trees counted and 4,525 park trees. The relative worth of the trees was calculated by multiplying the size, species class and condition. Condition not only includes the health of the tree, but its placement.
Some trees have a poor condition rating because they are located too near power lines or sidewalks.
Species class expresses the relative desirability of a tree species, broken into five classes. Class 1 is most desirable and Class 5 is least desirable. The desirability guidelines come from the International Society of Arboriculture. They include such factors as resistance to breaking up in storms, good shade, disease and insect resistance and ease of care. Anderson said just because a tree doesn't have a Class 1 desirability rating doesn't make it a bad tree.