Avoid pruning trees and shrubs starting in late August, particularly hedging plants such as boxwood, hemlock, and hollies, as doing so this late in the season can stimulate new growth that will not harden off before frost. If spring-flowering shrubs are pruned now, you will be sacrificing next year’s flower. Delay pruning any tree or shrub until the plant is dormant. Any major pruning should be done in late winter.