Chysanthemums.

Basically, you don't want to cut back any plant that is marginally hardy, or might have problems with wet getting into exposed crowns.

What mad-gallica said is all that really must be left up. You can leave up plants that do not turn to mush after frost such as wildflowers (e.g. Echinacea, Rudbeckia, etc.) because (1) their appearance can be attractive during the winter (2) the seeds provide food for birds and (3) next years butterflies pupate on the dormant stems. If it turns to mush (e.g. hostas) you should remove it because it could harbor pest eggs or fungal spores. After that, it comes down to personal preference. Some prefer to take down Echinacea to prevent heavy re-seeding. Some prefer to leave them up to feed the birds and provide shelter for them. Some do a little of both. Some plants, like Monarda, should be cut down to prevent incubation of disease. I always cut back the beds that are visible to people walking by for the same reasons you want to.

Here is a link that might be useful: More information

Thank you both that is very helpful.

Now I have a couple plants that I am not sure about since they are semi-woody.

How about these specifically:
Nepeta
Gaillardia
Russian Sage
Aster
Sheffield Mums

I cut some of these back last year and they came back fine, but we also had an unusually warm winter so not sure if it was pure luck.

Thanks!

I cut all my gaillardia, nepeta, and asters in the fall. Russian sage I wait until spring to see where the new growth is before cutting.

While I have read that it is best to wait until spring to cut back buddleia I prefer to cut mine back in the fall and cover the crown with several inches of mulched leaves. One I have had for at least ten years and the other is about five years old. I also cut back my buddleia seedlings last fall and they survived as well. In my Z:4 buddleia gets cut back to ground level.

At least here (and in New England), last year was not only very warm, but extremely dry. Given that your normal temperatures aren't really pushing these plants, the dryness is probably more important than the warmth. A normal Eastern winter is very wet, and made even more so because things don't freeze and stay frozen to lock the water up in ice.

The common nepeta varieties are pretty bulletproof. New England asters are natives, others can be tricky. Gaillardia I would not cut down. It has a reputation as a *very* short lived plant, and doesn't need much encouragement to die. Russian sage can probably handle being cut down in Jersey. Here it is just plain tempermental. Sheffield seems to be a very vigorous, good grower. I've cut it down.

None of these are particularly rare or expensive plants. If it would make you happy to cut them all down, do it. The worst thing that happens is they die. Then you need to decide whether or not to replace them.

Gaillardia, Russian Sage, and Asters normally do not require winter pruning. Pruning them back in Fall probably won't cause any harm, but they don't typically require it. If you cut back, I would leave all basal foliage (also leave 2-3" of the old stems as sometimes new basal growth emerges near and slightly above ground level stems). I leave my Gaillardia up all winter because it seems to improve their survival chances. Russian Sage tends to stay attractive-looking in the winter in warmer climates but in cold ones (Z4-5) they can get zapped pretty good and should probably be cut. You can cut asters to prevent re-seeding or improve appearance. Some varieties' (e.g. 'Monch') winter survival is improved by leaving them up (like mums).

The mums are probably best left alone until new growth in Spring as they overwinter better this way.

Nepeta looks pretty bad after a few hard frosts and should be cut down to basal foliage then for appearance reasons.

Thank you all for your help. The answers are exactly what I was looking for and at the perfect time...about to go outside and do the last garden work of the year until Spring. Always enjoy this part though as it really helps me plan what is changing for next year.

Here's a link to an article discussion which plants to prune in the Fall.....

Here is a link that might be useful: Perennials to Prune in the Fall

And another list of what to prune in the Spring....

Neither list seems complete though.

I lost a few Buddeia until I started pruning them in the Spring.
I never prune Perovskia or Lavender until the Spring
I leave the grasses up bc I like to look at them over the winter

With the changing weather, where it is now warm into November and sometimes into December, I find it confusing. Even those plants that you could prune back in the Fall, I hesitate, because I think with the warm weather, maybe the plant would start growing again, which I wouldn't want. So I actually leave a lot more for Spring than I actually have to. And I would like to prune more back, and I might but probably later in January rather than now.

Here is a link that might be useful: Perennials to prune in the Spring

Those are helpful lists Prairie Moon, thanks for posting them.

Agreed about lavender and Russian sage: I have read that fall pruning reduces winter hardiness, so I always prune them in the spring.

Top choices for fall pruning are plants that are messy (nepeta) and mushy (shasta daisies), plants in high-visibility areas or locations that interfere with snow shoveling, and plants that leaf out very early (columbines). I also try to do a fall cleanup in gardens that have a lot of spring bulbs so that the bulbs can be unencumbered by old foliage in the spring.

But the biggest factor here is when the first snowfall arrives. Some years I can keep doing fall cleanup right through Thanksgiving weekend. Other years, an early snow catches the garden midstride, with wheelbarrows and other utensils still in play and temporarily lost under the snow. That's what happened this year. I got a pretty good start on the ritual of cutting back, but then I left for a trip and came home to snow cover that will likely persist until April. Oh well! Time to go skiing I guess! :)

The "book" says to cut brunnera down in fall because of the ugly black foliage. I have found my 'Jack Frost' overwinter better if I leave the the black glob til spring.

tj

I'm like you, I like clean gardens that I can enjoy in spring with very little work. The only plants I don't cut down are tree peonies, roses (I trim them in spring after winter-kill is obvious)and spring blooming clematis.
Heather