These plants benefit from timely trimming of old growth. Perennial color plants will partially or totally die to ground each winter and will need the old growth removed to look best each spring. Perennials that die to ground completely should be cut to remove all dead material, but those that do not die to ground benefit from partial cutting to stimulate new growth that is fuller and more colorful than on plants not cut. For ornamental grass the cut is important to remove the previous year’s growth and allow new healthy growth, if not trimmed the old foliage contributes to crown rot, leading to dead or unsightly clumps of grass.