Ornamental grasses are perennials valued for the texture, movement, and vertical structure they bring to a landscape. They often remain visually appealing throughout the winter, providing contrast when other garden elements have faded. Pruning the previous season’s growth is a necessary annual task that encourages fresh, vibrant foliage and maintains the plant’s health. A clean cut allows the grass to redirect energy into new growth, preventing old, dead material from smothering developing shoots. The precise timing and method of this cut are determined by the grass type and are paramount for ensuring a successful growing season.
When to Perform the Cut
The ideal window for pruning most ornamental grasses is late winter or very early spring, just before new shoots begin to emerge from the crown. Waiting until this time allows the hollow stems to provide valuable insulation, protecting the plant’s central growing point from harsh winter temperatures and moisture. The dried foliage and seed heads also offer visual appeal when dusted with snow or frost, extending the garden’s season of interest.
This timing also benefits local wildlife, as the standing stalks and seed heads provide shelter and a food source for birds during the coldest months. Cutting back too early in the fall is discouraged for most deciduous varieties because it removes the protective layer and exposes the plant’s crown to damaging winter moisture and freezing. The most important rule is to complete the cut before the plant breaks dormancy, as severing new green shoots can permanently damage the foliage tips for the entire season.
Warm-season grasses, such as Fountain Grass (Pennisetum) and Maiden Grass (Miscanthus), should be cut back to a few inches from the ground. Cool-season grasses, which begin growth earlier in the spring, require a less severe trim, typically removing only about two-thirds of the foliage while leaving one-third of the plant intact. Knowing the growth habit of your specific grass variety is important to avoid over-pruning, which can be detrimental to cool-season types.
Essential Tools and Preparation Steps
Gathering the correct equipment is the first step toward achieving a clean and efficient cut. Protective gear, including sturdy gardening gloves, is necessary because many ornamental grass blades have sharp, serrated edges that can easily cut skin. For smaller clumps, a sharp pair of pruning shears or hedge shears will be sufficient.
Larger, more established grass clumps often require heavier-duty tools. An electric or gas-powered hedge trimmer can slice through dense, woody centers more quickly and with less effort than manual shears. Regardless of the tool chosen, ensuring the blades are clean and sharp is important to make a precise cut and reduce the risk of introducing disease.
A preparatory step that significantly simplifies the pruning process is bundling the grass clump before cutting. This involves tightly wrapping the foliage together with rope, twine, or bungee cords. Tying the grass into a secure column prevents the stalks from scattering when cut, allowing for easier cleanup and disposal. For very tall or wide clumps, it can be helpful to secure the wrapping in multiple places along the length of the stalks.
Technique for a Clean Cut
The physical technique for cutting most dormant, deciduous ornamental grasses involves a single, clean cut across the bundled stems. For warm-season grasses, the optimal cutting height is typically between four and six inches above the soil line. This height is sufficient to remove all the dead foliage while avoiding damage to the plant’s crown, where new growth originates.
Cutting too close to the ground can leave the crown vulnerable to water accumulation, which may lead to rot or frost damage in cold temperatures. The cut can be made flat across the top of the bundle or shaped into a slight mound, which some gardeners prefer for aesthetic reasons. When using power tools, use a blade that is wider than the bundled column to ensure a straight and even trim.
Grooming Evergreen Varieties
Evergreen and semi-evergreen grasses, such as Blue Fescue (Festuca) or certain sedges (Carex), require a different approach and should not receive a hard cut. These varieties retain their green foliage year-round and only need light grooming to remove dead or brown tips and spent flower stalks. Instead of cutting the entire clump, the dead material should be selectively pulled or combed out using gloved hands to preserve the existing structure and appearance.