Depending on how quickly temperatures develop in spring, you should cut the grasses back close to the ground early so that the perennial can sprout new shoots unhindered. Don't miss the moment; if the first green stalks push into the old clump from below, you'll inevitably cut them off too, and you'll still notice this later. So check regularly to see if anything's happening. Candidates for a "brush cut" include: Chinese silver grass (Miscanthus), fountain grass (Pennisetum), moor grass (Molinia), and diamond grass (Calamagrostis). Tip: Tie the clumps together beforehand; this makes cutting easier!
Caution: Wintergreen grasses such as sedge (Carex), marble grass (Luzula), and hair grass (Deschampsia) should not be cut back! They should only be pruned—that is, dead stems and old flower heads should be removed.
