Mary H. Meyer, Extension Horticulturist and Professor, University of Minnesota
Early spring or late winter is the best time to cut back ornamental or landscape grasses. Their winter appeal is usually low now, stems are likely partially down from numerous snowfalls. Hand cutting, an electric hedge trimmer, or a lawn mower set to the highest setting can be used to clean up the tops of grasses.
All warm season grasses, such as Miscanthus, switchgrass, big and little bluestem, along with prairie dropseed and Indian grass die completely back to dormant buds at the crown of the plant. You cannot cut these grasses off at “too low” a point. Their buds are at the root-shoot junction often buried in the soil. Tie large tops together to make them easier to cut. Cut warm season grasses back as low as your tools can reach. These grasses are slow to green up in the spring, so you have a few weeks to do the cut back.
Cool season grasses however such as feather reedgrass (Calamagrostis), blue oat grass, blue fescue, tufted hairgrass (Deschampsia), most Carex, or sedges will start to grow as soon as temperatures warm in the spring. Plant to clean up these grasses as soon as possible, before they start to green up. Feather reedgrass is so popular now (Is it overplanted?) and actually will grown much better if it is cut back early before any new growth begins to show. Tufted hairgrass is very similar to our lawn grasses and will begin to green up very early so cut back any brown foliage and the old seedheads now. Again, cut as low as you can, leaving 1-3 inches of stubble is fine. Other cool season grasses that are semi-evergreen, such as blue oat grass, blue fescue and many of the sedges, you may only need to rake the foliage with your hands or with a hedge rake to remove brown foliage, leave any green foliage. With sedges, cut off any brown edges of tattered leaves, leaving green foliage.
Ribbon grass is the showy white rhizomatous grass that can be invasive, and it one of the easier to control by mowing it off: in early spring as a clean up and again anytime during the year when it begins to look brown and drab. New shoots will be fresh and colorful, and this will help to keep it in bounds.
|Mowing ribbon grass keeps it in bounds and is an easy spring clean up. The foreground has been mowed and the background right is about to be mowed.|
A good rule of thumb for grass cut back is: if its brown cut it down. Spring cut back opens up the crown of the plant to rain and sunlight, allowing it to green up faster. Grass tops decompose quickly in the compost pile, if necessary cut the taller stems into half or 1/3 to fit into your pile.