Why Cut Back

• Ornamental grasses can become deficient in calcium and magnesium and need supplemental fertilization.Warrick Page/Getty Images News/Getty Images
  
  Grasses should be cut back annually to help stimulate and make room for the following year's growth. Old growth left behind from the previous year can prevent the new growth from receiving the early spring sun by shading it and can delay its emergence by several weeks. Ornamental grasses can lose some nutrients by the annual cutting back and should be supplemented with an all-purpose fertilizer such as a 10-10-10 at a rate of a half to 1 pound per 100 square feet.
  
  

When to Cut Back

• Grasses can have winter interest even when not actively growing.Jupiterimages/Photos.com/Getty Images
  
  Ornamental grasses need to be cut back before new growth starts in the spring. It can be done in the late fall, but ideally it should be done in late winter or early spring. Leaving the foliage intact for the winter allows for the canopy to collect snow and act as insulation for the root system over the winter. In areas of the country that do not receive snow, the canopy still acts as insulation.
  
  

How to Cut Back

• Make sure the cutting tools are sharp to avoid jagged cuts.Hemera Technologies/PhotoObjects.net/Getty Images
  
  Ornamental grasses should be cut down to ground level. A variety of cutting tools can be employed. Hedge shears, both electric or hand-held, can be used. Hand pruners, saws and even gas-powered string trimmers can effectively cut back ornamental grasses. Afterward, remove the clippings either by hand or with a rake. Don't allow cuttings to decompose in place. Failure to properly clean up can prevent good growth the following season.
  
  

Dividing Grasses

• Ornamental grasses can be divided by shovel, axe or saw.Hemera Technologies/PhotoObjects.net/Getty Images
  
  In addition to cutting back grasses, every three to four years they should be dug up and divided. If this maintenance is not done, grasses get thin in the center and eventually die. Divide warm-season grasses such as fountain grasses, Japanese blood grasses, Miscanthus species and plume grasses in the early spring. Fall is when cool-season grasses such as blue fescues and feather reed grasses should be dug up and divided.