How to Trim Ornamental Grass for Winter
Ornamental grasses are very low maintenance plants. Depending on their growth habit and your climate they may require very little pruning to extensive hard pruning each year. In warmer climates where the foliage does not die back in winter, maintenance pruning to keep the plant looking tidy is all that is required. In cooler climes where the grass top foliage does not overwinter, the foliage should be shorn away in the late fall or early spring.
Inspect your ornamental grass regularly during watering time to look for damaged, broken, during or diseased stalks or stems. Cut down any of these that you find by placing your cut at the base of the stalk and pulling the cuttings from the clump of grass. Discard the cuttings into the trash bin, bypassing the compost pile in order to avoid spreading the grass seed where it may be unwanted.
Prune your ornamental grass in the late fall or early winter in climates where the grass tops live through the winter. Remove any damaged stems or stalks and clean any grass material that has fallen or is lying on or near the ground. This tidying will help remove any elements that may be vulnerable to disease over the winter.
Shear off all the grass's top foliage with shears in the late fall or early winter after the grass has gone to seed and the first hard frost has occurred. Do this in climates where the grass tops do not overwinter. Make your cuts just an inch or two above the crown of the grass and discard the off cuts. If you hard prune in the spring be sure complete this process in the early spring to make room for fresh growth to emerge unobstructed by the dead grass.
Water your ornamental grass well after any significant pruning. This will reduce stress on the plant and help protect the roots against winter drought conditions. Mulch around the base of the grass clump or over the sheared crown with shredded bark, cocoa bean hulls or compost. This will add moisture to the soil and roots and keep any competitive weeds at bay. Mulch will also fertilize the grass as it breaks down and combines with the soil.