Hi Gilbert, I like to let stand Buddleia and Perovskia

I like to leave everything as is through the winter, unless it is something that I want to broadcast lettuce seed over. (Ex: cut back some ruellia yesterday so I could plant more lettuce mix and edible kale.) Generally in the fall I will plant winter herbs such as cilantro and chervil near my dormant daylilies and they will just take over and hide the old foliage. Course I am in a bit warmer climate than you... I know old foliage on things like daylilies will just compost on site and be gone by spring.
I do plan to go out someday soon and cut back my zinnias so I can scatter their seeds.
I have read where some marginal plants - esp. woody ones - will make it through the winter better if left alone. If you cut back, you open up an area for moisture to collect over the winter and this can lead to rot. ~ Suzie

This is just my 2 cents. I only cut back foliage, not stalks or seed-pods, in order to add a little verticality and winter contrast. I try to remove any leaves that might mat down under the snow and contribute overwintering vectors for vermin and disease. After the holidays, I collect discarded Christmas trees (and not a few decorations) and cut off the branches and lay them over the beds as a winter cover. I stand the trees upside down, holding the trunk in one hand and hacking off the branches with a machete. The branches are easy to lay down and remove in the spring if you lay them with the ends all facing the same direction. I place them with the tips toward the center of the bed, the cut edges at the border, then work my way down the opposite side, ending up with a kind of herring-bone look. I put the trunks across the top of the branches until we get enough snow to hold them down in case we get high winter winds... not that unusual in coastal Maine.

Come spring, the branches go thgrough the chipper and are spread around the blueberries and raspberries. I use the tree trunks as trellises and supports for the pea fencing. After about 3 years, the trunks are decomposed enough to either go through the shredder or into the fall campfire.

I leave the foliage and seed heads on most of my perennials during the winter. I cut them back and clean them up in early spring.

There are a couple of reasons why I wait till early spring to clean up...once I trimmed/pruned back all my perennials in the fall, only to find we had a really warm spell and the perennials that were cut back sent up/on lots of new growth...only to be froze back in just a week or two.
Another reason for leaving seed heads attached is for the birds to have during the winter. Gold finches and other birds love Black Eye Susan seeds, echinechea (coneflowers)seeds, plus many more.

I leave all mine attached till I cut back my fountain grasses ( about Feb. or March).

tammy

I'm in Zone 6. CT.

1. I have already mulched my beds with leaves (I raked them in there from the grass).
2. I haven't done any cleaning up at all, and won't until the spring. Prefer to have something, even dead stalks, to look at in winter, plus the dead stuff helps to hold the snow to protect the crowns. It also helps me remember where stuff is planted, next spring, before I accidentally digu it up.
3. I leave everything.

My beds are mulched and new flower areas of now lawn have about 1 foot of compost/leaves/horse + rabbit manure sitting on top. I do mulch the beds heavily to protect crowns and the more tender/newer plants. I wait until spring to cut most things down things. I like to leave the roots in the soil to decompose if I do cut down anything, like sulphureus cosmos. I also left the nicandra stalks up about 2 feet as a reminder for me to NOT walk into the garden...lol. I did prune some trees recently since they're dormant. My spring cut-down/trim list that I can think of right now is: perennials, ornamental grasses, caryopteris, buddleia, Pee Gee hydrangea and bittersweet vine.

I cleaned up this past weekend. My reason? I don't get enough garden time during the winter months and miss it. When spring comes I can find plenty to do :) Plus I do have lots of small new plants in my yard and want to protect them this year.

I agree with Bill in Maine--I also use my xmas tree branches that way.
Julia in Salem, MA