Most clumps of ornamental grasses increase in size enough that every few years they may be divided to start new plants. I find it easiest to dig up the entire clump in early spring before growth begins. (If you haven’t already cut back last season’s growth, do so before digging up the clump.) Slice through the clump with a sharp spade, shovel, or ax. Small clumps may be split in halves or quarters. Larger clumps may yield a dozen or more new divisions. Just make certain that each division has healthy roots and several growing points. Set the divisions in their new location at the same depth they were previously growing. Keep the transplants well watered until new roots are established.