They spread their arches across the streets like the graceful supports inside Gothic cathedrals. We have an intensive program of Dutch elm disease prevention. The pruning of the trees is done in the winter, because at that time, all beetles are inactive in our climate, and forestry work crews have fewer duties elsewhere. Manitoba maple is the worst bleeder of any tree around here, and it needs to be pruned in the heat of summer, July and August, when the water supply is too low to facilitate bleeding. Pruning at any other time may cause months of bleeding, thus exhausting the tree.
Green elm follows the same rules are Manitoba maple.
Evergreens Evergreens are pruned for effect and to slow growth. Christmas tree stands of Scotch pine get annual haircuts to produce a compact shape. Don't look at those trees too closely, because the branches get an unnatural appearance which bothers me. I seem to feel the tree's pain at having its limbs shortened indiscriminately. I might also compare it to cutting off fingers instead of fingernails.