Answer: You can leave the tops alone until frost kill the stems, then remove any browned portions. Next spring, trim them back again. As you probably know, container plants are always more susceptible to winter damage because there is less insulating soil around their roots and crowns. If you opt to keep them in the planters, and the species you have are cold hardy for your area, shelter them from wind and insulate the roots by wrapping the sides of the containers or settling the pots into the ground. Once the ground freezes you could also lay some evergreen boughs or similar light and fluffy mulch over top of them to prevent damage from freeze/thaw action in the soil. Snow cover provides even better protection. You could also try protecting them in the garage. If your basement is heated, the plants may not go into dormancy, but there probably isn't sufficient light to keep them healthy and growing. But you can try that as well. You might want to try a couple different methods to see what works best for the plants you have. Best of luck!
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