What Tool to Use to Cut Back Ornamental Grasses

Shears

• Smaller ornamental grasses, like mounding fescue (Festuca ovina), yield easily to a pair of pruning shears. Manufacturers categorize pruning shears as either anvil shears, where the blade closes against a stop, or bypass shears, where the blades pass each other like a pair of scissors. Either shear works, although bypass shears are more efficient when dealing with small grasses. Sharp shears slice through tough grasses much easier than worn, dull blades; sharpen your shears annually or after particularly tough jobs.

Clippers

• Hand-held clippers or electric hedge trimmers suit fountain grass (Pennisetum alopecuroides) and other mid-size grasses. Using using either tool generally requires two hands, which leaves the cut grass to fall haphazardly and results in a messy, uneven cut. Instead of fighting the falling grass, tie string or twine a few inches above the planned cut, and tie a second line around the center of the stand. This holds the dead grass in place as you operate the clippers.

String Trimmer

• While string trimmers snip small grasses down to size, standard string trimmers won't last long against an established stand of large grass, such as larger cultivars of Japanese silver grass (Miscanthus sinensis). The string quickly breaks, or simply whips against the tough, sharp blades until it pulverizes the plant. To make clean cuts on larger grasses, replace the string head with an adapter designed for tough jobs. These adapters usually have jointed, short blades that spin like a power saw and make quick work of thick, moderately large clumps.

Chainsaw

• Large stands of pampas grass (Cortaderia selloana) may grow up to 12 feet tall, and giant reed grass (Arundo donax) may grow up to 20 feet tall. When ornamental grasses reach this size, a standard trimmer literally isn't going to cut it. Instead, use a chainsaw to make a clean cut, roughly 6 inches above the base or above any visible new growth, in late winter or early spring. Grass blades are quite sharp; always wear gloves when cutting large ornamental grasses.