- fall-blooming ornamental grasses usually remain gorgeous well into the winter. It seems a real shame to cut them back to the ground before late winter or early spring. Some gardeners are now waiting even beyond THAT, and enjoying the effect of wheat-colored grass clumps contrasting with spring-flowering bulbs!
- seed-heads of certain perennials provide food for finches and other birds, and they look great against a blanket of snow. Most late-flowering daisy-type perennials are on this list (like Rudbeckia and Purple Coneflower), but others with nice seed-heads and sturdy stems include: Achillea, Agastache, Aster, Astilbe, Baptisia, Buddleia, Chelone, Cimicifuga, Eryngium, Eupatorium, taller Sedum, and a few others.
- there is a common theory that the dead tops of perennials help to trap the snow, which is the very best insulation against cold temperatures. In regions with erratic snowcover and mid-winter thaws, the tiny bit of extra snow that is actually trapped may in fact be of little benefit.
- many perennials have very little winter interest. Cutting these types back in the fall effectively "clears the clutter" and makes the ones you leave look even better. Consider cutting these down in late fall: Alchemilla, Anemone, Campanula, Centaurea, Coreopsis, Delphinium, Dicentra, Euphorbia, Geranium, Hemerocallis, Hosta, Lychnis, Monarda, Nepeta, Oenothera, Phlox (tall types), Trollius, Veronica.