Gardeners often ask, "When is the best time to cut back the dead tops of herbaceous perennials (stems die back to the ground each year)? Should we cut them in fall as the tops fade? Or wait until spring, just before new growth begins?" The answers depend, in part, on the specific plant and whether disease or insect pests are a factor.
For most healthy plants, leaving plant tops over winter is fine and, in many respects, preferable. Many species retain dried seed heads and foliage that may have aesthetic value. Ornamental grasses are at their best in fall and winter.