To prune or not to prune that is the question. With the arrival of fall perhaps you’re considering cutting back your overgrown lilac or that evergreen taking up more than its fair share of the sidewalk. Set down the trimmers and walk away. You’re better off raking leaves, flipping mulch, and planting pansies. Extensive pruning in the fall can have a negative impact due to unpredictable weather. For example: October begins cool and plants are moving into their dormancy period.