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You are here: Home / Containers / How to overwinter perennials in pots

How to overwinter perennials in pots

By Beckie Fox Filed Under: Containers, November in the garden

Hostas are easy to overwinter in containers.
Hostas are easy to overwinter in containers.

Herbaceous perennials in pots — plants that die back and are dormant in winter — that have been part of your summer container displays need to be protected over the winter if they’re going to survive and bloom again next year. Here’s how to overwinter perennials in pots.

Hardy perennials have roots that sleep until next spring, which is when they begin to put on new growth. A few examples are hostas, Shasta daisies, heucheras, astilbe, lady’s mantle and daylilies. To overwinter them successfully, you need to keep the plants dormant and provide a winter environment that’s within their hardiness zone. A plant growing in the ground is more protected from severe cold (and alternate freezing and thawing) than one in a container; therefore, a plant that’s hardy to your zone usually needs extra protection if left in its container.

After a couple of killing frosts, water plants thoroughly and choose one of the following three options for overwintering:

Option 1. Leave the planted container in its current location. If the container is large and able to withstand the elements, and if the plant is at least one zone hardier than your area (i.e., if you live in Zone 5, herbaceous perennials in containers need to be hardy to Zone 4 or lower), the likelihood of successfully overwintering the plant in its pot outdoors is high. A large container holds more soil, which helps insulate roots and keeps soil temperature consistent. However, when sun hits the sides of a container, especially a dark-coloured one, alternate freezing and thawing may trick the plant into thinking it’s spring and trigger early growth, when it’s merely a warm day in February.

Option 2. Move borderline-hardy plants or those in small containers to an unheated garage or shed to increase survival odds. Because the plant is dormant, light isn’t required for photosynthesis, but do check every couple of months to make sure the soil isn’t bone-dry. Don’t overwater, however, as this could cause plants to rot or break dormancy.

When growth resumes in late winter/early spring, reintroduce the plant to normal growing conditions outdoors by gradually exposing it to the elements for increasing periods of time.

Option 3. Find an area where you can sink the plant and its pot into the ground so the roots will be better insulated. (A vegetable garden often has unused space.) Cover the plant with two to three inches (5 to 8 cm) of winter mulch, such as shredded bark or leaves. In spring, remove the mulch and lift out the container.

Published: November 14, 2015 | Updated: November 2, 2018

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About Beckie Fox

Beckie is Editor of Garden Making. She is a Master Gardener and published author in Niagara-on-the-Lake, Ontario.

Reader Interactions

Comments

  1. Joyce Dyer says

    November 18, 2020 at 8:40 am

    What is the best way of over-wintering a Red leaf HEUCHERA that is still flowering?

    Reply
    • Beckie Fox says

      November 19, 2020 at 10:58 am

      Depends on a lot of factors. The larger the pot, the better the chances the heuchera will overwinter. If you’re in Canadian Plant Hardiness Zone 5 or warmer, this will help its chances of success, too. Move the pot into a sheltered location– an unheated garage or shed — if you can. Also, the pot itself needs to be winter-hardy. Terra-cotta or ceramic may not make it through the freeze-and-thaw cycle of winter. However, if the heuchera you have is in a small plastic grow pot, find a spot in your garden and bury the pot and plant up to the rim. Cover with shredded leaves and dig it out early next spring.

      Reply
  2. Linda says

    June 13, 2020 at 9:04 pm

    I live in southeastern wisconsin. I planted a red sentinel in a large pot today. The pot is too large to move in winter. What do u suggest?

    Reply
  3. Tina says

    May 20, 2020 at 7:23 pm

    I am in zone 2b. Will delphiniums and columbine survive in pots if i keep them in an unheated porch over the winter? My beds need more work than I anticipated when I bought the bedding plants

    Reply
    • Beckie Fox says

      May 21, 2020 at 5:06 pm

      My prediction would be no, unless they are in very large pots. If you could get the perennials into the ground by late summer/early fall — even in a temporary nursery bed — they would have a better chance of survival.

      Reply
  4. Cathey says

    September 8, 2019 at 1:53 am

    I live in zone 7b in NC, which we get much colder and hotter than the chart says. I planted many of my hostas in nursery pots, then sit them inside of the decorative pots, which I matched for height and size. In the summer I take out the nursery pots if we have had to much rain so the plants can drain well. During winter I take out the nursery pot and turn the decorative pot over them ! For those which are planted directly in the large decorative pots, I remove the drain pan underneath and place over the top. Also I huddle them closely together as I can move them. This has worked for me for 20 years.

    Reply
    • Someone says

      May 22, 2020 at 12:24 pm

      This is a great idea. Thanks for sharing. My zone is slightly warmer than the plants I want to keep. I have only a couple places to keep them cool in the winter. Mulching or burying is not an option. I had not yet considered the temperature difference an additional layer if air between a pair of pot walls could offer. Your success over time using this method gives me some hope!

      Reply
    • C Murphy says

      July 4, 2020 at 12:43 pm

      Excellent information, just what I was looking for. Thank you.

      Reply
  5. Abby says

    November 15, 2018 at 8:48 pm

    I went crazy this year and bought way to many perennials (mostly Hostas) to plant. Now we have snow and short, below 0 days. I started to dig a trench in the field and put them in sideways, in the pot. I am putting some leaves on the top/open side of the pot and barely covering the whole pot over with dirt. Next I am covering with a plastic tarp. What do you think my chances are and what else would you suggest? I am zone 4

    Reply
    • Marcia says

      December 3, 2018 at 12:31 am

      Just saw. My friend owns a nursery and told me to put a sheet under plastic tarp to keep plastic from burning plant where it touches. I am going to get some kind of winter protection clith from him –10 by 12 — for 13.99 dollars. Call a local nursery and they can suggest.
      Just another plant lover.

      Reply
    • Susan Smith says

      October 18, 2019 at 7:00 pm

      I leave my potted hosta, daylilies and several other perennials in the pots outside and just turn them upside down… in the spring I turn them upright and water them… They survive beautifully !!!! I live in zone 5 winters are quite cold !!!!

      Reply
  6. Carol says

    November 4, 2018 at 2:22 pm

    Wondering how to winter some potted hostas…. We live in the Blue Ridge Mountains of Virginia and I have used these on the porches all summer. Would the plants survive if I tip them over and nestle in the leaves and foliage of the day lilies in the flower bed? This bed is located on the west side of the house…..
    Thanks for your advice!
    Carol

    Reply
    • Carol says

      April 9, 2019 at 2:51 pm

      UPDATE to my post: April 9, 2019. Just went outside to see if the hostas had survived the cold Blue Ridge Mountain winter…….. Very HAPPY to say that all 4 pots show the beginnings of new growth. I am so glad that they survived! 🙂

      Reply
  7. Janice says

    June 20, 2018 at 5:33 pm

    If you wrap the planters in burlap and cover the top with woochips, will the flowering plant servive winter? Thank you.

    Reply
  8. Kris says

    May 5, 2018 at 9:45 am

    I have 4 Alberta Spruce in planters and would like to know if I can leave them outside for the winter. What can I do to protect them from Ontario winters?

    Reply
  9. Kathy says

    November 1, 2017 at 8:12 pm

    Hi Becky – I am moving from my GTA home in March and have several perennials, including a couple of rhododendrons, in plastic/wire pots (now in decorative containers) which I’m planning to take with me. I’m wondering if it would be a good idea to take them out of the decorative containers, leave them in the plastic/wire pots and wrap them with landscape fabric to keep the soil moist and together ready for transporting. I could take them now before the winter to a friend’s backyard and cover them with leaves as well. What would you recommend? Would a protected north exposure or more open south exposure be better? Thank you.

    Reply
  10. Pamela Sargent says

    October 20, 2017 at 11:57 am

    Hi Gail
    We are scheduled to move in November and I want to bring my perennials with us – phlox, bachelor buttons, daisys, peony, astilbe, wind flower and roses. I have a friend who has offerred her raised bed veg plot to me for the winter. Should i pot these guys up or plunk them right in?

    Reply
    • Pamela Sargent says

      October 20, 2017 at 11:58 am

      We are in Hardiness zone 5…coastal Maine.

      Reply
    • Beckie Fox says

      October 25, 2017 at 8:42 am

      I’d pot them up in moistened container soil in old plastic grow pots that have drainage holes, then plunge them into your friend’s raised beds. Cover the tops with two or three inches of shredded leaves. You can nestle them quite close together. The aim is to keep them from freezing and thawing throughout the winter. Remove them early next spring and replant in your new garden. Good luck!

      Reply
  11. C. Kirkland says

    October 14, 2017 at 10:49 am

    I have had great success by getting ahead of the game and buying spray in foam that comes in a can and spraying the inside of the pot before putting soil in. I spray a one to two inch layer around the inside of the pot. Because you spray it on, any shaped pot can be treated. I did this 15 years ago to my outdoor pots and the foam is still holding up and my plants have lived very well.

    Reply
    • Maria says

      August 30, 2018 at 9:39 am

      C Kirkland, what is the name of the spray foam that you used? I want to try this but don’t know what kind of spray foam is safe for the plant.

      Reply
  12. Janet Dedicik says

    October 14, 2017 at 8:13 am

    If these excellent methods of keeping perennials is not practical, I have a suggestion that has worked for me for many years. I dig the, mostly trailing perennials, out of their pots, wrap all the trailing branches around the root ball and bury them deep in my compost pile. When we open the pile in the spring, voila, all the plants are alive and well. I cut off the dead trailings and replant in my pots. Works like a charm.
    I live in southern Quebec, close to the Vermont border.j

    Reply
  13. Judy losier says

    October 13, 2017 at 8:49 pm

    I have very good luck overwintering plants even in small plastic pots. We have lots of snow & they get buried pretty deep.

    Reply
  14. cindy says

    August 15, 2017 at 8:23 am

    I live in zone 5 (zone 7 depending on who you ask) on the coast of Lake Erie. I want to over winter potted perennials for the first time.I have black eyed susans as well as mexican heather in pots that I would like to save. Any advice would be appreciated.

    Reply
  15. dave pounds says

    June 4, 2017 at 11:34 am

    Hello Gail
    I am planning to try a trough garden using an old concrete laundry sink.
    I am in the Alliston Ontario area, in a fairly sheltered valley Zone 4/5 ish.
    I will be planting Alpine plants…….what should I do to insulate the whole trough over the winter…??? Would you recommend placing the sink on the ground or could I get away with insulating the space between the supports if I lift it up…???
    dave

    Reply
  16. Melissa says

    May 21, 2017 at 11:15 am

    I am wanting to plant boxwoods in my tall plastic planters for the deck. I live in Saskatchewan where the winters can be a little harsh. Just wondering if you would know if they would survive a winter left in the planter on the deck .

    Reply
    • Beckie Fox says

      May 21, 2017 at 5:41 pm

      Unfortunately, I doubt the boxwoods would survive your winters. Perennials and shrubs overwintered in above-ground containers need to be two zones hardier than your growing zone. Also, plastic isn’t a very good insulator.

      Reply
  17. Annette Roskar says

    November 17, 2016 at 10:28 am

    How about plants in pottery or ceramic pots. Will they crack when the soil freezes? Also, if I plant spring bulbs in a pot and place it in an unheated shed, will it survive the winter? Should they be lightly watered during this time. Thanks

    Reply
  18. Gail Wood says

    November 10, 2016 at 9:05 pm

    I’m trying Option 3 with some roses that I won’t be planting till next spring. I put the plants and pots in the ground and covered them with an extra 2″ of soil. They’re in an area that is sheltered from the wind and I’m also going to spread mulch over them. Do you think they’ll survive?

    Reply
    • Beckie Fox says

      November 11, 2016 at 8:57 am

      Hello, Gail: I think your roses have an excellent chance of surviving. By sinking the potted roses into the ground, you’ve provided necessary insulation to the root balls. Once the ground freezes and the plants are totally dormant, pile some shredded leaves or mulch over the tops of them for extra protection. Your aim is to keep the plants dormant until spring by preventing fluctuating winter temperatures from thawing, then freezing, the roots. It’s usually the alternate freezing and thawing that harms plants over winter, not the cold itself. Next spring, gradually uncover the tops to allow warmth and sun to reach their branches. Once the danger of hard frosts has passed, you can transplant the roses to their permanent locations.

      Reply

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