Walk down almost any street and you'll spot boxwoods (Buxus sempervirens) edging yards or framing walkways. Pruning in spring, by contrast, gives them the best shot at healthy, dense growth. These hardy evergreens grow slowly, so even small pruning mistakes can have a lasting effect on their shape and fullness. The problem with pruning in the fall is that it pushes the shrubs into new growth just as they should be settling in for winter. Come spring, boxwoods are primed for trimming.