I feel guilty if I don't get my stuff cut down in the fall....and many years I spend the winter feeling guilty! LOL!
I think about the only things that really do better if you leave them over the winter are mums. It won't hurt most other perennials if you leave them or cut them....but I hate to face that mess in the spring!! And if you have any diseases, bugs or fungus going on, it's good to get the leaves and stuff out of the garden.
Linda C

Any plants that develop a more or less woody stem structure (Buddleia, russian sage, lavender, caryopteris, clematis and many other vines, etc.) that remain above ground and could experience dieback in a cold winter should be left until spring. Otherwise, you can cut them back/clean them up at your discretion. Like Linda, I don't like looking at that mess overwinter and have more free time in fall, so I do it then.

I cut back lots of perennials in the fall, just so the beds look clean. I do like to leave a few standing-Liatris for birds, ornamental grasses and Astilbes, just for winter interest.

Jen

Another woody perennial that should not be cut back in fall is gaura. The *only* way I have been able to get it to survive reliably is to treat it as a subshrub, and leave it alone until growth begins in spring. Waiting for spring is not that difficult, but waiting for the new growth to being is definitely tough!

The only plants I cut back in fall are ones that can carry disease, like peonies. Everything else stays until spring, partly because I don't like the looks of "neat and tidy" empty beds, partly because I like leaving cover for birds, and partly because I'm a lazy procrastinator.

marjirose, we had a very mild winter, overall, in the northeast, and that may be one reason your butterfly bush did so well. I wouldn't try cutting it back in fall again, though, just in case we have a "normal" winter.

Like Diggingthedirt, the only thing I cut back in the fall is the peonies. I leave everything else in place - both perennials and annuals.

There are several reasons for this. I kind of like the "messy" look, and enjoy the foliage as winter interest, especially when there is a snowfall. The foliage provides some wind and privacy screen along the front of the house during the winter when things are bare and the winds coming from the farmland across the street are just brutal.

Also, the standing plants catch lots of leaves that blow around in the fall/winter and this provides mulch for the gardens over the winter. In the Spring I actually just rake or pick out whatever stray foliage remains and continue to use the leaves as mulch. Last but not least, the birds enjoy picking through the leftover seedheads and the foliage provides places for beneficial insects to over-winter.

Anyway, I definitely wait until early-mid Spring to cut back the Buddleia, just about the time I see new shoot sprouting. And yes, once cleome gets going, it re-seeds prolifically - but I love cleome, and use it and other annuals to fill in between the perennials and shrubs.

The only things I cut back in fall are my peonies, my lilies, if I get to all of them, also plants that showed signs of disease, powdery mildew etc. Otherwise it stays till spring as it helps to catch leaves and snow if we get any. Haven't had much the last few years.

Along with gauras, the western Agastaches should also be left until spring. Cutting them in fall brings water into the crown and they generally die. A. foeniculum (anise hyssop), the blue agastache, can be cut back in fall. And I also agree that all woody sub shrubs should never be cut in fall--often kills Buddleias.

If you grow roses you know that it is critical that the canes be left until the following spring. Current thinking is that the plant needs the sugars stored in those canes even tho they are dead. It may be true of other plants also.

I definitely don't like bare earth look. I like to see the bones of last season's garden standing thru the snow. I don't deadhead the last flowers of fall so the birds eat the dried seedheads. Peony and iris foliage has to go but the rest stays until April.

In the Fall, I cut back anything that I don't want to go to seed, the peony foliage, Phlox paniculata hybrids (to prevent disease) & anything that I don't like the looks of. Leaving dead foliage helps insulate some plants & I'm usually too busy in Fall dealing with the raking to have much time for Fall garden cleanup aside from the things listed above that need cleaning up. In Spring, I'm so eager to do anything in the garden, & cleanup is something that can be done while waiting for the soil to become plantable.

I do both. I definitely cut down and throw away peony and iris leaves.
I cut down veronica, cat mint, yarrow, salvia but leave up mums, asters, boltonia, coreopsis. I figure most of the second group survived for years without our help in this climate and catch leave in their stems for their own protection. I do trim the tops a bit though. I leave up the liatris but cut down the coneflower and especially the black-eyed susans. I know you are supposed to leave the seedheads for the birds, but I've never seen any come and partake. Instead, if I don't cut them down, I get rudbeckia seedlings all over my garden. I prune roses, Russian sage, caryopteris, buddleia, smoke bush in early spring.

I also vacuum up the leaves, mulch them and put them back on for winter protection. Then I toss on a couple of branches from the Christmas tree.