I'm a lazy autumn gardener. A lot of gardening experts recommend leaving dead, dried stems and foliage on some plants for "winter interest." When I first heard about this "technique" a few years back, it became my formal explanation (excuse) for following the practice. In all honesty, I simply lacked enthusiasm for bothering to cut them back. This autumn laziness stands in stark contrast to my generally boundless energy in mid to late spring, when I spend as much time as I can in the garden.
But there's one plant I always cut back in autumn--Peonies (Paeonia lactiflora). I just cut mine back today. The reason: Peonies are susceptible to wilt, a fungal disease, so it's important to cut off all the old growth and burn it or discard it. I've heard and read various opinions on how far back to cut the stems. Some experts recommend leaving a few inches above the ground; others say to prune to below the soil level. I usually leave about one to two inches of stem above ground. I leave cages around the stems, and pack lightly with Oak leaves. My theory is that this provides a structure of warmth under the mounds of snow that cover the plants from December through March.