Wondering when to trim back your ornamental grasses? Here’s the scoop from the OSU Horticulture & Landscape Architecture Department!
Ornamental grasses should be cut back in late winter before new growth emerges. It can also be done in fall, but the seed heads provide nice winter interest, and some birds will also feed on the seed. To make the job easier, tie up the stalks with string. Depending on the size and density of the grass, the following tools might be used: house scissors, shears or hand pruners, and electric hedge trimmers (for very large clumps). For smaller grasses, trim to about 2 to 3 inches from the ground; for larger grasses cut 6 to 8 inches from the ground. One exception is with the species Nassella (Stipa) tenuissima, Mexican Feather Grass, it does not respond well to heavy pruning and prefers to only be cut back by 1/3 to 1/2 its height.