Wintering pots

nancyjeanmcAugust 15, 2006

How do you "winter over" the pots. Anyone have luck leaving them outside, or are most planted with annuals??


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jenny_in_se_pa(USDA7 Sunset 32)

Where I am, everything I have out there Zoned 5 or less stays out with no protection. Plants that are Zoned 6/7, I'll protect and sometimes will bring in if there's a cold snap. Here were some of my plants this past February (all that were buried in the pic had some perennial or shrub or bulb in them except the window boxes):

The one thing to keep in mind is that the bigger the container, the better it can overwinter. Also the composition of the pot might be of concern as types like clay, terracotta, and ceramic have a potential to crack due to expansion and contraction from freezes and thaws. The synthetics (plastic, resin, foam) or concrete, cement, metal, wood (for a bit), etc., fare better in the weather.

    Bookmark   August 15, 2006 at 7:32PM
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Wow...that's some snow. Thanks for your help. You said you "protect" some of the pots/plants. Just by bringing them in or is there another way. I don't really have anyplace to put them inside. :(

    Bookmark   August 16, 2006 at 5:41PM
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jenny_in_se_pa(USDA7 Sunset 32)

By "protect", I mean that I'll pull them against the balcony wall. In that case, if they're small enough, I'll put them under a table against the wall. You could get insulation or bubble wrap or old sheets/towels, etc., and wrap marginal plants and place against the wall and out of the wind. Grouping containers together also helps.

This past winter I decided to try something akin to a cold frame at least to keep some plants out of the wind. Ie., I had a no-longer-used "console" humidifier unit (which is basically a big plastic rectangular box on wheels that holds a resevoir jug and filters which I removed), and placed some of my small container shrubs in that (1 gallons mostly) and surrounded them with pine needles.

It'll really depend on the winter and how low the temps go from winter to winter. New plants are more tender than established ones - even within the same designated hardiness range, so if you can get them through those first couple winters, then they'll usually be fine later in their life. Getting them big enough to go into larger containers also helps in that regard.

What plants do you have that you want to overwinter?

    Bookmark   August 17, 2006 at 10:07AM
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I also keep container gardens in plastic "window-box" type pots and haven't been able to keep them from dying. My problem is my "garden" is a south-facing balcony in an apartment building. Shade cloth around the perimiter of my balcony has helped during the summer to keep my garden from getting too much sun, but what do I do in the winter?

As I live in an apartment building, I have no access to a garage or unheated storage area, nor can I plant anything in the ground that others might dig up and throw out or take. Does anyone have any more detailed suggestions as how to winter perennials on a balcony in containers? I have strawberries, a blueberry bush, lavender, and rosemary that I'd like to try and save this year.

My thoughts were to try a clear plastic bag tied loosely around the entire containers (with the 'tied' end up to allow a bit of 'breathing'), with extra straw packed around the base to try and protect against too much cold.

Would this work? Any suggestions?

    Bookmark   September 3, 2006 at 11:19PM
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jenny_in_se_pa(USDA7 Sunset 32)

Dawn - This is sortof a timely thread now because that time is coming soon (sigh). I have to really think about this for myself too since I have a big pile of new plants this year that need to be established.

You might want to try to find very hardy plants rated 1 -2 zones colder than you, which would be a good first step (I list some of mine below that you could grow). There are a couple Zone 5 posters here who will hopefully weigh in.

Straw would be good to try (I have packed some young transplants and marginals in pine needles). Pulling the plants against the wall and grouping pots together will help to keep them out of the prevailing winds and will help maintain a more constant temperature around them. You might want to consider some white reflective plastic (rather than clear) to keep the sun away from them in winter, as the south-facing spots still do get sun in winter, whereas in my NE-facing location, I get none in winter. The sun issue is because you want to avoid continual freezes and thaws and sun on plants during mid-winter will trigger that (and can scald the plants).

What kind of blueberries do you have? The northern types are usually hardy to your Zone and there have been some bred to Zone 4 like 'Northblue'. But you may want to protect it to keep the branches from dessicating and the container from freezing too much, as they would be considered marginal in a container for you. Believe it or not though, snow is a good insulator and I have used it for my plants against the rail. I have 5 blueberries ('Bluecrop', 'Nelson', 'Elliott', and 2 'Patio').

The strawberries could stay out, although you may want to keep them back out of the weather as often rot from perpetually wet and cold soil can kill them more than any cold.

The rosemary isn't going to survive outside and will need to be brought in. The lavender (depending on type) is iffy - even here in my area in the ground, mostly because they like it dry in winter, so you might want to bring that in too. One of my sisters has been babying a lavender growing against the SW corner of her house and it still got some winter damage, but not as bad as when she had it out in a bed in her yard.

I have some marginal perennials and shrubs (along with subtropicals) and I have to bring those inside. I generally put them in my bedroom in winter, which I keep cool (low - mid 60 Fs). Otherwise they'll die. I do have a couple high-light subtrops like some habaneros that I have overwintered for 4 years and I usually put those under lights, although I may consider doing something else for some of those.

An alternative which I haven't really tried but others have, is to construct a small greenhouse or cold frame that you can vent on warm days and heat on very cold days. You can buy remote temperature probes (I have 3 myself) and place one in the structure to monitor the temp inside.

I have some plants reported as hardy to Zone 4 like:

Lilac (S. patula 'Miss Kim')
Weigela (W. florida 'Red Prince') *
Weigela (W. florida 'Wine and Roses') *
Orienpet lilies
Salvia nemerosa 'May Night'
Hydrangea paniculata 'Grandiflora'
French pussy willow (S. discolor)
Lady fern
Monarda didyma 'Jacob Cline'
Royal Heritage hellebore %
Agastache rupestris
Mandarin honeysuckle (L. x mandarin) %
Coral honeysuckle (L. sempervirens 'Blache Sandman')
Prickly pear cactus (O. humifusa)
Clematis (C. viticella 'Prince Charles')
Rainbow leucothoe (L. fontansiana 'Girard's Rainbow') * %

* = these get winter damage/tip burn even in Zone 7, so Zone is probably more 5 and for the leucothoe, its evergreen leaves need some wind protection

% = these are either evergreen or try to stay evergreen (honeysuckle), but can crisp up in cold temps.

I also have a new sambucus 'Black Lace' that can reportedly survive to Zone 4 if protected per a thread on the Far North forum.

Some of my Zone 2/3s include:

Lilac (S. x prestonia 'James McFarlane')
Heuchera (Heuchera x brizoides 'Firefly') %
Bleeding hearts (Dicentra spectabilis)
Redosier red twig dogwood (Cornus sericea)
Variegated red twig dogwood (Cornus alba 'Elegantissima')
Hostas (H. albomarginata, etc)
Dianthus gratianopolitanus (Cheddar pinks)
Sarah Bernhardt peony
Tree peony 'Seidei'
Daylily ('Pardon Me')
Sedum 'Autumn Joy'
Siberian columbine (Aquilegia sibirica 'Biedermeier')
Asiatic lilies
Tiger lilies
Lily of the valley
Crocuses (spring blooming)
Muscari %
Mints (peppermint, pineapple mint)

% = evergreen or has foliage up in winter

None of the above are protected at all and usually stay put where they grow in summer, although I sometimes pull smaller pots back and sit them on or under a table against my wall. I have some Zone 5s like my penstemon 'Sunburst Ruby', blueberries, Methley plum, american wisteria (W. frutescens 'Amethyst Falls'), and Itea virginica 'Little Henry' that I can do similar to. I also have Zone 6/7 marginals (for me) like Beautyberry (C. bodinieri 'Profusion' and C. americana), golden bamboo, Salvia subrotunda, crocosmia 'Lucifer', and some Salvias (S. guaranitica, S. microphylla x greggii 'Red Velvet'), a crape myrtle (L. indinca 'Victor'), Tea shrub (a pink blooming, red leaf Camellia sinensis), cannas, and calla lilies, where I have to decide how to protect (eg., keeping out as long as I can and then possibly bringing them in during cold snaps).

My Zone 8s and above (coffee arabica, pineapple sage, tropical hibiscus, pentas, pointsettias, christmas cactus, etc.,) have to come in.

My hardy perennial herbs like my pineapple mint (the peppermint stays in a trough), lemon thyme, and greek oregano are in small pots and may get brought in for winter, although I may just stick them under a table outside so I can water them as needed.

    Bookmark   September 4, 2006 at 12:10PM
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Thanks Jenny for all the excellent advice!

My blueberries are Northland variety from Vermont and has done quite well, 12" of new growth in one season, about 1 & 1/2 cup of fruit first season (lucky me!). I potted in a 12" dia. pot using a mix of light potting soil and peat moss to keep the soil acidic -- this was just on my my observations that the soils in northern WI where blueberries grow wild are very acidic, so I thought that would be good for them. I read later that blueberries in fact need acidic soil, so I was glad I thought right :) I'd like to have some more varieties, but don't have any more space I'm afraid!

Wintering plan for bluberries: keep them where they are after pruning (they are in a corner of the balcony fence, 60% sun screen on 2 sides) and let them fend for themselves, maybe piling leaves or snow on them to help insulate.

Wintering plan for rosemary: dig it up and bring inside.

Wintering plan for strawberries & lavender: group pots against wall, pack with dry straw, and cover with white plastic.

Wintering plan for Asiatic Lilies: group them with other pots, pack with straw, and hope they come back again next Spring.

Well I sure feel better now that I have a good plan! Now I can relax and wait until all my Morning Glory seed packets have matured enough for me to harvest them, and think about what I might add next spring. Thanks for that list of what you use ... after perusing this forum, I'm glad I'm not the only one out there who's trying to keep bushes and perennials in a container garden on a balcony!

- Dawn

    Bookmark   September 4, 2006 at 1:17PM
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jenny_in_se_pa(USDA7 Sunset 32)

Your plans sound good! I know I better get moving with a plan too. LOL My morning glories are spilling seeds all over the place, guaranteed to sprout in almost every pot next year. 8-)

As an FYI regarding the blueberries, if you want to keep them on the acidic side, you can mulch with oak leaves (shredded would probably be easier if possible - I was gathering some at my sister's house and fertilize with Hollytone, which is an all natural fertilizer and acidifier for acid-loving plants. I use it for my blueberries.

    Bookmark   September 4, 2006 at 7:36PM
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Hi Dawn,

I am a zone 5 container newbie, and I am thinking about all this overwintering stuff, too. I have 2 blueberries (Darrow, to zone 4) that I was going to do an experiment on - bring one into the garage, and leave one on the balcony. But one is not looking so good, so that would hardly be a fair experiment LOL. I may just leave them both out there since that is easiest (garage is 4 flights of stairs away.) I have a huechera that I just left out last year due to laziness, knowing absolutely NOTHING since my mom bought it for me as a housewarming gift, and it made it through just fine. I have a strawberry container filled with some perennial herbs and some not (parsley?) so I will bring that in for the winter to see what happens.

As to the future, I aspire to growing many perennials that just stay on the deck, inspired 100% (no joke) by Jenny. I also want to start a little fruit orchard - Meyer lemon, figs, avocados - things that will stay in my bedroom with lots of southern light over the winter. I saw a nectarine zoned to 4 that I may try to keep outside (next winter since I don't even have it yet.)

It's exciting, isn't it?!?

    Bookmark   September 7, 2006 at 10:20PM
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I have heard that putting styrofoam or styrofoam "peanuts" in the actual pot, linning, works as this true?

    Bookmark   October 25, 2006 at 1:33AM
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Browsing the web today and came across gardenweb and signed on. I'm hoping members will be able to help a new gardener in need!

I have two rose bushes, lavender, 12 little boxwood seedlings and 2 hydrangeas all in plastic containers that I would like to keep for the winter. I am limited to my high-rise balcony in Stuttgart, Germany (zone 6?. I'll need to bring the plants inside or leave them outside--in ground is not an option. I'm really tight on space inside, but if I had too, I could find space for the hydrangeas since I can't bear to see my 30Euro plant freeze over the winter!

Thanks in advance!

    Bookmark   November 7, 2006 at 11:21AM
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Dear Jenny,
I hope you go on reading these pages.
I am a newcomer to this forum, I came accross it searching the internet for an idea as I couldn't find a satisfactory answer for my problem. I've just read your posting on wintering pots. Obviously you are an expert on that. I grow a honeysuckle in a pot on my balkony. I started to propagate it the summer of 2005. This summer it bloomed and made a number of vines, some of them being about 6 feet long. It is the first winter I have to care what to do with it. I asked an agronomist and she suggested that I don't take it indoors but to isolate the pot in some way. I did it and we had already one night with temperature about 23F (-5C). The leaves in the morning were not in normal shape, kind of frosted, so I couldn't stand that and moved it indoors - on a place between the apartments which is not heated and has some light. That was about 2 weeks ago. Today I saw that the leaves of the plant are falling and as the weather is now quite better (38F at night and 60F at daytime) I took it back to the balkony. Now I really wonder how to proceed.
I love this plant and maybe next spring will find where to plant it in a garden so that I don't torture it this way.
Don't know what type of honeysuckle it is, I can tell only you that its flowers are white and become yellow when grow old.
Please help!
Mariana, Bulgaria

    Bookmark   November 15, 2006 at 7:43AM
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jenny_in_se_pa(USDA7 Sunset 32)

Hi Mariana - Sorry for the late responses here! I have been sortof busy at work and dealing with the balcony... LOL

I did see your post and responded here.

To kanada - I think your roses may be okay outside as long as you keep them protected and keep the soil protected so it doesn't get wet other than from what you give it. That's because soil that stays too wet and cold in winter can rot the roses and/or possibly kill the top graft (if it is a grafted type). The lavender may not be hardy outside in a container if it gets too cold. The hydrangea may be okay depending on what type it is - some are very cold hardy like H. paniculata (I have one of those). Some others like H. arborescens is pretty hardy as well. The popular H. macrophylla is tricky because except for some of the newer cultivars like "Endless Summer", etc., that bloom on new growth, it isn't bud hardy in U.S. Zone 6 or colder and would require alot of protection to be able to get blooms the next season. The boxwoods, as babies, may need to come in too since they are babies. As they mature, they should do better outside in winter, although as evergreens, you would need to make sure they get wind protection (perhaps using burlap around them).

To canadiancat - A number of us have tried the styrofoam peanuts and I think they are helpful in terms of keeping the temperature around a pot constant so that once the soil is frozen, it stays frozen (thus reducing the freeze/thaw that can actually be what kills a potted plant in winter).

To containergirl - Many have inspired me! This is why I have so much stuff out there!!!! LOL!!!!

    Bookmark   November 19, 2006 at 2:09PM
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