I would recommend planting them in pots and burying the pots in your garden bed since it's in a sheltered spot. You should be able to just cover them with straw just like the other plants. I wouldn't cut the foliage back unless it looks like it could possibly have diseases.

Yes, it's perfectly fine to plant swamp milkweed in pots. I put the plants in 3-gallon pots because I plan to keep them year after year (crossing my fingers that they make it above ground during our winters). The seeds need a period of cold, so you can either put them in the frig for awhile before planting in the spring or do what I did and plant them in pots in the fall and they will sprout in the spring. I'm not sure how cold it gets where you're at though. Maybe you'd have to put yours in the frig first if your winters don't get very cold. I know that ours get plenty cold. I kind of wish swamp milkweed would have another name because for one thing, I think maybe people probably do assume that they need to be in a swampy area to do okay, but that's not true. They do fine in pots or in the garden. We had a drought this year and mine didn't die. Of course, I did water them occasionally just to make sure they pulled through. I'm talking about the 100 plants that I planted in a bed of their own. I just started them this year, so you'd think if they'd have died any year from the dryness, it would have been this year because of both their young age and the drought. Another reason why I wish swamp milkweeds would have a different name is because maybe people who aren't familiar with them hear the name and get a mental picture of some horrible-looking plant. I would recommend not planting them in just one-gallon pots if you're going to let them grow and not cut them back at all. I had bought some in one-gallon pots at the nursery in the late summer of 2005 when I was just starting my butterfly garden and those plants were so tall compared to the pot and not much weight in the pots with just that small amount of soil that the plants/pots kept falling over before I got them planted in the garden. Cathy

Commercially they keep them for three or four years. Just be sure the roots don't stay too wet through the winter. When growth starts in the spring trim the old foliage off being careful not to cut into the crown. Al

10 degrees warmer than the outside air temperature has not much to do with ground temperature, and freezing and thawing. We don't know just how much warmer it is under snow cover but igloos will raise the temperature inside by 30 or 40 degrees warmed by body temperature alone. Even half that beats your garage and there's not the fluctuation in temperature you would get in a garage. I'd sink your pots into your vegetable garden and throw some leaves over them. I'd do the same with the ones in your raised bed and I'd pile leaves or straw around the outside of the raised bed. That should get them through the winter just fine.