Most perennials are cut down in fall after frost. Exceptions include Gaura, western (dryland) Agastaches and western Salvias. Leaving the foliage helps keep the crowns dry during our wet winters; it's the wet, not the cold that does them in. Other perennials that people often leave until spring are grasses, tall sedums, and any others that look interesting in the winter garden. Some people leave seed heads of a number of perennial for the birds, but I find that the reseeding that occurs causes me an enormous weeding problem, so I don't let any perennials seed about.

If you have Buddleias (Butterfly Bush) I would not cut those down in the fall. Cut them back to 6 inches from the ground in the spring when they start showing new growth. My experience is that I lose any which are trimmed back in the fall.

The seed heads which I leave for the birds in the winter are the coneflowers. Finches really appreciate them in January when there is little food elsewhere and if they do reseed you can easily pull them.

Might get a more exacting answer if you listed the perennials you have in your garden - and even then it often comes down to a personal preference of doing a clean up in the fall or leaving the clean up until spring. In many cases (but not all) it doesn't matter to the plant.

I prefer a fall clean up and cut down peonies, daylilies, tall garden phlox, iris, Siberian iris, veronicas, nepetas, hostas, bleeding heart, lilies, salvias, penstemon, balloon flowers....

I don't cut back Russian sage or the sedums.

The only things I try and clean up are plants with diseased foliage and peonies. A lot of phlox with mildew this year so I will get those. The rest, I leave until spring.

I cut most everything down except plants that are quite low to the ground. Sedum in the Spring and roses of course. Some ground cover I leave too, they are low to the ground. I put bone meal around everything just scratch it in, gives them a good start in the Spring. My dog doesnt bother it, but the dog next door, tries to get at it, so may want to keep an eye on it. I have a fence between us. Never had that before. Good Luck! Tricia

With the exception of certain plants (many mentioned above), whether you cut down in fall or Spring is sort of a personal preference. I leave most things standing for winter interest, seeds for the birds, and screening. Dried grasses are very ornamental, and the stalks and seedheads of certain plants look attractive covered with snow. The stalks catch blowing leaves and provide a nice mulch for the gardens over the winter (this might not be good if you have a problem with moles and voles).

But I do some deadheading and cut down Peonies, Lilies, anything that is diseased, scraggly annuals, tomatoes, and a few odd things in the fall.

It makes for more work in the Spring, although most of the perennial stalks are wisps of their former selves by then. The dired stalks and blades of grass can get a bit messy by Spring.