It is an herbaceous perennial and as such once it is killed by frost in the fall you can cut it back to a couple inches above ground level. If kept in that container, you may want to keep it in an unheated garage over winter and put a snowball on it once or twice a month for just a little bit of moisture. Don't let it become a block of ice. tj

You will probably find you get as many answers here as you have found on (the rest of) the Internet. That said, my own approach is that if there is not a reason to take something down, leave it up. Reasons to take something down would include: (A) ugliness (there are few that fit into this category for me, I like the different elevations and textures as the season develops, and some things (e.g., ornamental grasses) are positively lovely); (B) disease/pests (though I personally don't subscribe much to this one, especially since along with overwintering pests will be overwintering beneficials); and (C) unwanted seeding. Many of your identified plants are rampant self seeders but the "damage" is already most done for them (e.g., get ready for LOTS of brunnera, plenty of pulmonaria, a bunch of new Echinacea/Rudbeckia and lots of Monarda!). But again, this is not a bad thing depending on your goals. New plants, free, are not a bad thing and you can also weed out or pot up and give away unwanted plants. And while they may not be true to their parents they might be even better, and lots of plants have a habit of popping up in just the right place. In case you haven't noticed, I am in favour of not doing much in the winter by way of clean-up. But I have done it both ways (sometimes with a lawn mower!).

Thanks for the useful tips, pirate_girl. Probably I'll do it in summer. ltecato, my plant is outdoor in summer (June - October) and indoor in winter. Another thing I noticed is airing my living room. My neighbor's plant is hanged at the window (actually glass wall) that never open. Mine (in a wall planter) is hanged near my glass door that I open wide thrice daily to air my room. Every time I open it for 5 minutes. It could be the problem, as now the temperature outside is -7C. Some aloes that I put at the same place were died (collapsed), it could be due to the sudden cold. Another thing I noticed was, when I removed the rotten plant, ( I did it before starting this message) the root was OK, the rotten part was the stem above soil. It could be that some water was till there, when I aired my room. Now I reduce the time to 1 - 2 minutes. jefe12234, thanks for the advice. I'll do it in summer. Now after the whole action. It's looks OK. So I won't touch it till spring.

Daylillies get the flower stalks removed, and in most cases the leaves will wilt with the first good frost, and can be raked away. the coneflower can be cut down to about a foot (if you want more, saving the seedheads will accomplish that- but they reseed themselves readily) if the peonies are just ragged looking, leave them until frost. if they're powdery looking (mildew) or spotty, cut them down. ALWAYS dispose of peony foliage- it and rose clippings are some of the few things that almost never go in to the compost heap, they're too prone to carrying disease. the snapdragons can indeed be harvested for their seeds- if a hybrind variety, you will get a 'random' mix of results next year. if they're a standard or heirloom kind, you'lll get pretty much what you got this year. the butterfly bush? kinda depends on what you want from it. some people like them light and airy and huge- they get trimmed to shoulder height, and thinned a bit. some whack them all the way back to knee height once they go dormant, then clean up any crossing trunks. me ? I'm trying something new I saw at Longwood Gardens- I'm training mine in to a tree- removed everything but one upright trunk, staked it in place, and am whacking it back to just beyond the top of the trunk, forcing it to put out side branches, which then also get trimmed- you might know the old clairol commercial, where two friends becomes four becomes eight becomes enough to fill the screen, yes? same principal. any loose litter, sickly looking leaves, and dead branches should be removed, and a top dressing of compost followed by a winter bed of mulch is always good :)