Hedge trimmers tend to work better on the larger, older clumps of grass and the thicker-bladed varieties like Miscanthus, or Pampas (Erianthus). Newer, smaller clumps of the thinner-bladed varieties, like the feather reed grasses (calamagrostis), and the fountain grasses (pennisetum) can be trimmed with the hand-held pruners.
Lift the dead plumes off the grass plant with the bungee still wrapped around the bunch, and deposit them into the compost pile. Scratch out, or remove, any dead or decayed stems that remain in the center of the grass. Depending on the age of the clump, a dollop of compost in the center can stimulate new growth in that area. Over time, as the center of the grass dies out, the clump can be divided and shared with neighbors.
Your ornamental grass is now ready for new spring growth!