That is the question: Whether 'tis nobler in the garden to suffer the slings and arrows of a million outrageous Echinacea seedlings next spring, or to wield pruners in the autumn against a sea of slug-infested Hosta foliage and by cutting, end their miserable looks for the year.*
I'm not embarrasssed to say that I'm an obesessive-compulsive gardener. Some people proclaim fall their favorite season. Not me, thanks. Bushels of leaves that drop the minute you finish mowing the lawn, peonies that have succumbed to measles and powdery mildew, daylilies that continue to produce brown leaves as soon as you groom them. Wow- what's not to love about the fall garden?
There's something soothing about the aesthetics of a clean fall garden. It's a little like getting the kids tucked in and asleep before Santa arrives. Smug satisfaction, for sure. How nice not to have Calamagrostis refuse rolling like so much tumbleweed over the winter lawn. We don't want our Arborvitae splayed open. Why should ornamental grasses be different? Certainly if you desire "tidy" and cut your perennials back in the fall try to wait as long as you can. If the plants are in full color they're only getting stronger with each additional day they make and store food. In a perfect world, we'd wait for at least one hard freeze before reaching for the pruners and machete.
Consider your schedule. Isn't fall really a slower gardening time for you than spring? What happens when snow sticks around and soil stays frozen? Or, it rains and/or gets warm early and new growth starts emerging through last year's detritus. It's hard to name another gardening chore that's as tedious as pruning dead litter without damaging fresh new growth in the spring. Just my perspective.
Aphids, slugs, leaf spots, blights, pestilence in general, linger around those plants sticking out of yonder snow bank. Removing the debris in the fall, leaving stems 1-2" tall, theoretically reduces the overwintering populations of livestock and disease. Good fall garden hygiene should translate into fewer "pest" issues next year.
In the interest of balance and full disclosure, certainly there are things I leave standing. Of course, evergreen perennials (Iberis, Hellebores, many ferns, some true Geraniums and Bergenia, to name a few) must stay. Why not compromise? If you like the looks of a plant over the winter leave it. Weigh whether its winter long beauty is worth having to cut back in the cold, driving rains of March.
While I'll admit the sight of rabbits and deer (in my garden) raises my testosterone and blood pressure, there is something to be said for the cover and potential fodder that perennials afford wildlife. I do believe in doing whatever I can to create a healthy diet for our feathered friends- rabbits and deer, not so much. Admittedly, many perennials provide delicious life-sustaining seeds. That's a huge reason not to deadhead or cut back certain plants (Echinacea, Heliopsis, Rudbeckia, for starters).
Mother Nature always does things for a reason. Leaf and stem debris surely provide necessary insulation, probably increasing winter hardiness. Come to think of it, isn't that why we mulch? Still, if you're obsessive, maybe the compromise is not cutting back marginally hardy perennials in the fall. Leaving the foliage to keep the ground frozen may lessen the effects of the vicious freeze/thaw cycles that can wreck havoc on Midwest perennial gardens.
Another advantage in leaving perennials standing through winter is to mark the specific location of late-emerging species (Hibiscus is a perfect example, often not emerging from hibernation until June). That may prevent you from slicing through the crown with a well-intended, but misplaced, spade.
As I reread this it comes down to the old maxim, "Beauty is in the eye of the beholder." Your call.
*My apologies to William Shakespeare and my 9th grade Humanities teacher, Mrs. Ogden.