Ornamental grasses are perennial, clump-forming plants prized for their texture and movement. Gardeners often wonder whether to cut back the dried foliage in autumn or wait until spring. The correct approach depends entirely on the type of grass and the gardener’s preference for winter aesthetics. Generally, leaving the grasses standing through the cold months is the recommended practice, guided by understanding the plant’s growth cycle.
Understanding Warm-Season and Cool-Season Grasses
Ornamental grasses are divided into two categories based on their growing cycles, which dictates their maintenance schedule. Warm-season grasses begin active growth in late spring or early summer, thriving in high temperatures. These grasses, including Miscanthus, Panicum, and Pennisetum, flower and produce seed heads in late summer or fall. Once the first hard frost arrives, their foliage turns completely brown and enters a deep dormancy, making them the primary candidates for being left standing all winter.
Cool-season grasses grow most vigorously during the cooler temperatures of spring and autumn. They often remain semi-evergreen through the winter in milder climates and slow down when temperatures rise too high. Fescues, Blue Oat Grass, and Tufted Hair Grass fall into this group. Because their old foliage can sometimes mat down and hinder new growth, these varieties require a lighter trim in late winter or early spring and should not be cut back severely.
Benefits of Leaving Grasses Standing Through Winter
The standing, dried foliage provides several advantages, making the decision to delay cutting beneficial for the plant. The most significant benefit is the natural protection the dead material offers to the plant’s crown, the growth point where the stems meet the roots. This dense shield acts as insulation, guarding the crown against temperature fluctuations and extreme cold, which helps prevent damage from winter heaving. The structure also manages moisture around the plant’s base, preventing excessive water from pooling near the crown and leading to rot.
Beyond plant health, the upright stalks and plumes add considerable visual interest to the winter landscape. They catch frost and snow, creating sculptural elements, and their colors provide contrast against evergreen plants and white backgrounds. This standing vegetation also serves an ecological role by providing shelter and food for local wildlife. The persistent seed heads are an important food source for birds when other sustenance is scarce.
When and How to Cut Back Ornamental Grasses
The optimal time to cut back most ornamental grasses is in late winter or very early spring, just before new growth begins to emerge. This timing allows the old foliage to provide protection throughout the harshest weather. It also ensures the material is removed before the new shoots are long enough to be damaged, preparing the plant for its active growing season.
For large, established clumps of warm-season grasses, first gather the entire bundle of dried stalks and tie them tightly together. This bundling simplifies the process and makes cleanup faster and more efficient. Using sharp tools, such as hedge clippers or pruning shears, the tied clump should be cut back to a height of four to six inches above the ground level.
Cool-season grasses require a different approach because they should not be cut back severely. Gardeners should only remove about two-thirds of the height, leaving approximately one-third of the foliage intact. This selective pruning removes the faded, damaged material without compromising the plant’s semi-evergreen nature, allowing new growth to emerge cleanly.