HELP - are perennials still okay if frozen in pots?

brit5467(7b/8a Coastal VA)January 4, 2010

Been sick. Left potted perennials out in freezing weather. Dirt in pots is frozen hard now and a Coral Bells looks wilted. Are they all still worth planting? They're just sitting there in my new bed, waiting.

Here's what I have that I'm most concerned with (in 1/2 gal. pots):

`Russian Sage (Salvia Rusa)

`Palace Purple Coral Bells (Palacio Campanas de Coral Moradas)

`Walkers' Low Catmint (Paseantes Catmint Banjo)

`Coreopsis (??? nameless, got on clearance)

And in 3" pots:

`Lemon Balm (Melissa Officianlis)

`Lavendar (don't know what kind - pic looks bushy with shorter flowers)

When I just went out to get tags I felt them and some top dirt is thawing, but pots are still hard. Should I try to thaw them in the sun or let they stay frozen? (Dumb question but didn't know if shock between frozen and defrosted would hurt them?)

Also, I made mistake (??) of watering Coral Bells this a.m. because I thought dirt was dried out -- until I felt it and realized it was frozen. Will that hurt it? Most water ran straight thru, tho.

Just FYI, weather calls for even lower temps and possible snow by end of week if that has any bearing on your answer.

Also, if I can't get to them for a couple days, how should I protect them in the meantime?

Please realize my panic comes from being in Zone 7b and not used to really frozen ground so don't know if roots freeze this hard when in ground....duhhhh???

To summarize....have I killed my plants and if not, can they stay in pots somehow until I have time to plant them? Our ground will probably thaw in a week or so. Our weather fluctuates 10 to 20 degrees at times.



Bonnie aka brit5467

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Maybe and maybe not. I would plant them and see what happens
What I would do now is put the pots in something and shove newspapers down around the pots. The danger to perennials in pots is freezing and thawing and freezing again. If you can keep them frozen until close to planting time and then set them in the sun to thaw a bit before planting, they will have a better chance.

    Bookmark   January 4, 2010 at 12:00PM
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brit5467(7b/8a Coastal VA)

THANKS !! So I'm hearing that they DO need to thaw a bit before planting. Any reason why? (so I can learn more about what I'm doing).

What if top half is thawing now but bottom is still frozen? Should I hurry up and get out there NOW and take care of that (get them insulated) or can I plant them today with half thawed and half frozen?

I'm in a time crunch and I CAN plant today (but don't want to). Otherwise, I'll be waiting at least a week, maybe more and then there's no telling what my weather's going to do. It might just keep getting colder and colder...that being the case, I won't be able to thaw them ANY!!

Or it might jump up into the mid 40' telling around here :o)


    Bookmark   January 4, 2010 at 12:06PM
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brit5467(7b/8a Coastal VA)

Since you're online - know anything about pansies freezing in the same manner? Don't know what to do with them since the ones in 8" pots look frozen (wilted and stems damaged).

    Bookmark   January 4, 2010 at 12:08PM
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brit5467(7b/8a Coastal VA)

Just checked & now they are all thawed. So which is the lessor of the two evils? --

Put them somewhere thawed and prevent them from freezing until I can plant (at which time they'd freeze that nite) - or - make sure they freeze again NOW until I'm ready to plant, at which time I'll need to thaw first (and then they'd freeze that nite).

Trying to understand if extended length of being thawed is worse than letting them freeze again and then having to thaw.

Sorry I'm so 'dumb' about all this....

    Bookmark   January 4, 2010 at 12:46PM
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mad_gallica(zone 5 - eastern New York)

The freeze-thaw business was apparently invented by somebody who never spent time in the Mid-Atlantic area. As you know, every night it freezes, and every day it thaws. If this really killed plants, you would be living in a desert :-)

The problem with planting frozen pots is that you can't do anything to adjust roots if it's necessary. Also, if the pots are frozen, the top of the ground is also probably frozen. This makes it hard to dig.

Personally, I'd be much more worried about overall low temperatures than any freeze-thaw cycling. If it gets too cold (without snow cover) then the smaller pots should be moved to some sort of shelter. Window wells are popular, but often just next to the house works. Aside from that, I'm not sure how worried I'd be. I've left mums in pots outside in very cold Philadelphia winters without any problems. Who knows what I've got outside right now. Here, I try to round up all the plants in the fall because it can get cold enough here to cause problems, but some have known to escape.

    Bookmark   January 4, 2010 at 1:11PM
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mad gallica

If it freezes at night and thaws in the daytime the frost is not going very deep and chances are your plants roots are not really frozen. Plants in the ground aren't affected by frosts like those in pots or raised planters.

Here where it freezes hard for weeks on end and then maybe thaws a bit and freezes hard again it does kill plants, especially if they have no snow cover or protection. I have a friend that planted cedars in raised planters with no insulation. They grew wonderfully all summer and she left them all winter. In the spring they were dead.

You see like in all gardening your climate and others are different and what doesn't affect your plants in your climate does affect others in a different climate.

Brit--I should have looked at where you are from. Yes go ahead and plant them and your pansies too. One brief frost shouldn't hurt them and they are better off in the ground than in pots I hope they are thawed enough and the ground too so you can spread the roots out a bit.

    Bookmark   January 4, 2010 at 1:33PM
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brit5467(7b/8a Coastal VA)

Thanks to both of you. I just really don't have the concept down of what happens to the root system of plants when in the ground frozen versus being in pots. I worried that there was more of a vulnerability in the pots.

I guess since I have a bunch of leaves handy, I'll take all the thawed ones and stick them all together and stuff and cover with leaves for a few days in the sun.

Or actually, things don't seem to freeze on my porch, so I could just move them all up there for the time being. They'll get lots of sun in the a.m.

Speaking of insulating raised beds, I'd posted that question somewhere (?) about lining the sides with black plastic to hold in moisture. Got any ideas on that?

    Bookmark   January 4, 2010 at 1:44PM
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I'll agree that it depends :-)

You are correct to be worried. Plant roots - and this includes woody plants as well as herbaceous perennials - tend to be much more vulnerable to cold damage than does the topgrowth. This is a very thoroughly studied and well-documented phenomenon as it is of huge concern to the nursery industry as well as bonsai practitioners, etc. If planted in the ground, this is seldom a concern for zone hardy plants, as the extensive soil mass surrounding them has insulating capacities but if they are in containers and especially smaller nursery containers, that insulating feature is missing. It is the very cold ambient temperatures that surrounds exposed containers rather than the frozen soil that creates problems. That's why it is suggested that long-term containerized plants be at least 2 zones hardier than your own.

Often it can be as short a time as a few hours of temperatures in the low 20's to cause irreparable root damage - with other plants, the period of vulnerability may not begin for several days. It all depends on the specific plant. And you may not see the damage immediately. Often the topgrowth will remain looking OK until new growth is scheduled to commence in spring and then you'll see a rapid decline and even death. And this can happen here in zone 8 just as easily as it can in colder zones.

The best you can do for the plants now is either sink the pots into the soil or go ahead and plant as soon as the soil is workable. And hope for the best :-)

    Bookmark   January 4, 2010 at 3:04PM
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Your plants would be better off in the ground. Either sink the pots into the soil to the top or plant them. Sinking them in the pot allows you to check the roots for damage and decide where to plant them later.

Lining the planters with plastic won't hold in moisture, but it may impede drainage. Moisture does not escape from the sides but from the exposed soil. If you want to preserve moisture in pots then mulch the top of the pot. A layer of spagnum moss on top of the exposed soil in the pot will not only conserve moisture but look good too.

    Bookmark   January 4, 2010 at 4:07PM
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brit5467(7b/8a Coastal VA)

Thanks guys !! All the feedback is helpful. Not trying to be a smartass, but if I had soil to sink them in, they'd be sunk :o) Problem is, the raised bed is empty.

Before I got sick, I'd planned to just take plants out of pots, place them, then dump compost around them all. In fact, the whole purpose of building the raised bed was because due to wet soil, I could not plant them in my regular garden (still can't - mud) and wanted to avoid them freezing. The bed was 'supposed' to be my solution (not having to dig & just using compost).

Obviously, this did not happen... :o)

I wasn't able to plant today, so I've moved them onto my (open) porch. Things don't freeze as quickly there and they will get good sun early and for 3/4 of day.

But I misunderstood someone (in another post) and watered them all today. I think that was a mistake !!!

What are y'alls feelings on me having watered them this afternoon? They all have good drainage.

So now I'm considering running out in my p.j.'s and robe and moving them to my neighbor's garage (a pretty long trek, tho). Also, I still have a huge pile of leaves. What if I went and stuck them all way under the leaves instead of moving them to the garage?

I'll be able to plant them day after tomorrow and hope for the best.

Oilpainter, I think you misunderstood about the lining. You'd mentioned "a friend that planted cedars in raised planters with no insulation" so thought I'd pick your brain about raised beds. I meant just lining the sides (but not bottom) to keep the dirt from drying out so fast & to keep dirt from 'leaking' thru the cracks between the two posts.

    Bookmark   January 4, 2010 at 7:29PM
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brit5467(7b/8a Coastal VA)

Forgot about (deceased) better half's old shed. Went in and found oil circulating radiator type heater so put them all in there on very low heat. Should keep the freeze away. So that's solved. Tks for all the support !!!

But oilpainter, still wouldn't mind input on lining the raised bed.

Thanks all !!
Bonnie aka brit5467

    Bookmark   January 4, 2010 at 8:44PM
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Forget the plastic and mulch. A raised bed is like a big planter. The soil may shrink away from the sides and you may lose some moisture there, but it would shrink away from the plastic in the same manner, so what you would have is the same moisture loss. Look at any pot--especially a plastic pot-- and you will see what I mean. Mulch will prevent moisture loss over the whole bed including the sides.

    Bookmark   January 7, 2010 at 3:36AM
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brit5467(7b/8a Coastal VA)

Great !! Tks for that info. I was sort of worried about the wood 'sucking in' the moisture, as well as some of the fine dirt constantly 'oozing' out between the crack in the timbers since it sits along side my paver walkway.

But it's too much trouble, will take too much time and am running out of 'unfrozen' dirt days and am going to get out there right now and get the darn things in the ground !!! They are calling for snow tonight (a rarety here near the beach)!!

    Bookmark   January 7, 2010 at 1:36PM
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mxk3(Zone 6 SE MI)

I've been overwintering various plants (woodies and perennials) in pots for over a decade. The pots, those kept in the garage as well as left outside (hauled up against the house and barricaded from the wind) freeze rock-solid every single winter. And I've not lost one in all these years due to winter damage....

I'm with Mad Gallica on this one.

Plus, think about it - in my zone, the freeze line is lower than a good majority of perennial plant root depths and some woodie depths, so of course the root masses get frozen solid, even in the ground planted at the proper depth. Yet they still continue to return year after year.

    Bookmark   January 7, 2010 at 3:38PM
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For the non-believers out there:

"Essentially any type of container exposes the roots to ambient temperatures," says Dr. Hannah Mathers, assistant professor in nursery and landscape extension at Ohio State University in Columbus. Mature roots can gradually get used to the cold, but young, immature roots can't. In containers, young roots grow on the outer part of the rootball. When exposed to the cold, young roots are unable to acclimate and die back.

And, young or old, the roots are usually not has hardy as the plant's top. American holly (Ilex opaca) is hardy to USDA Zone 5. The top part (stems and foliage) of the plant will survive to a temperature of about -20 F, but immature roots die at 23 degrees above zero, and mature roots at nine degrees. In the ground and insulated by the earth, that's usually no problem for the roots of hollies in Zone 5 where the average minimum temperature is -10 to -20 F. But in a container, root damage in American holly would begin to occur at 23 degrees if left unprotected a drastic difference from -20 degrees.

From Clemson University: Unprotected Root Systems: Root systems that are unprotected above the ground are very susceptible to cold damage. This is especially true for plants in containers, planters or balled and burlapped plants. On some otherwise hardy species, lethal root temperatures can begin at 28 °F.

From Washington State University: Shrubs and trees which are growing in containers above the level of the ground are very susceptible to extreme root damage. The roots of plants are far less hardy than the tops and even normally hardy species can be killed outright if the containers in which they are grown are subjected on all sides to very low temperatures. This kind of damage is often not noticed until spring, when little or no new growth takes place.

From the Horticultural Research Institute:Of the $2 billion wholesale production of nursery plants grown in the U. S., about 50% are produced in containers. Freeze damage to the roots of container grown plants is the largest single cause of crop loss in the nursery industry. Differences in cold hardiness between roots and tops of woody plants can be as much as 16.7°C (30°F).

There is a vast difference in the cold tolerance of a hardy plant established in the ground compared to an unestablished one left in a small nursery container. That's why everyone goes to such lengths to provide winter cold protection for containerized plants. You may be able to create an adequate microclimate by grouping containers together in a protected outdoor location and covering or mulching well but their roots could still be vulnerable to cold damage. Many times this DOES occur but since the evidence of the damage appears so long after the fact, the gardener seldom puts 2 and 2 together and assumes poor garden performance after planting or even death is due to some other cause.

    Bookmark   January 7, 2010 at 6:14PM
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mxk3(Zone 6 SE MI)

Well, that's fine and all, but I've personally never had any problem with solidly frozen pots - and that's all I've got, folks...

    Bookmark   January 7, 2010 at 6:46PM
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brit5467(7b/8a Coastal VA)

Well....while you guys seem to be online at this very moment....let me read all you have to say since I have new questions since I just got them 'somewhat' in the ground....
Give me a few minutes....TKS!! And TKS for all the help...

    Bookmark   January 7, 2010 at 6:50PM
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brit5467(7b/8a Coastal VA)

Okay...JUST got done putting the new ones in bought on clearance a month or so ago. THOSE were the ones I was really concerned with because they aren't established.

Here's all the info. I don't think I ever told the whole story. It's a raised bed about 6" high. Built it Nov/Dec before all this cold. We had too much rain and too muddy to plant in regular garden so figured, hmmmm -- "raised bed" -- stick new plants in, throw in DRY soil around them and good to go.

BUT -- sh-t happens, THAT never happened, & I ended up with my current problem.

That being said, I guess there's some variables that might come into play with what you guys have to say.

These ARE new plants from big box stores which gardengal's info seems to relate to -- young roots on outer part of rootball are vulnerable. And I noticed them (fresh roots) when I planted them. BTW, great wealth of info, gardengal. TKS !!! And BTW, all the rootballs were very wet. One had that that funky, too much water stench.

Msk3 -- I get what you're saying, too. Somewhere else on this site (before I got myself into this trouble & was looking for solutions) there was a post all about overwintering pots outside, on their sides for drainage, etc. and people seem to do it all the time.

But it was mainly Northern areas and I got confused because I don't really know what 'overwintering' is with regards to doing it ouside??? Does that mean you dig up established plants?? And, not coming from your sort of weather (I see youre in MI with lots of snow, Im sure) -- why do you do it versus just leaving them in the ground? I'm not being a smart-ass, just uninformed. Because I CAN see where that may make a difference (established plant vs- new in pot).

Around here, snow is such a big deal that the city shuts down. Literally. I'm serious. So plants around here are 'sissy' plants...ha ha ha. Does snow have anything to do with it?

So mxk3, you could help me understand more by explaining about overwintering and why its necessary for you? TKS !! You can even email me if you wanna.

NOW, for my current dilemma -- I was able to put plants in bed with an inch of existing tilled soil mixed with store bought (bagged) compost/manure. BUT -- didn't have enough soil to fill whole bed and cover plants properly.

So I teased out bottom roots (and with some, pulled off a chunk of soggy roots) dug down 1" or so, set into place then dumped what little soil/manure compost I had into the bed and mounded enough around each one so crowns & entire root ball is covered. The mound is about 3 - 4" wider in circumference than the root ball. Had hoped that was enough protection.

Soooo.considering all that these plants have been thru, should I still go back out there and fill the bed with leaves? They arent mulched leaves. Just raked up leaves.

I ask because presently, it's only 32 (30 on Weather Channel) but we are expecting snow (ha ha...maybe, since we never get it this close to the beach. But it DID snow a little before Xmas). Tomorrow it will be warmer, but will drop into high 20's in evening for next few evenings.

However, tomorrow I plan to get more dirt, mix with my many bags of compost/manure (that I 'thought' I could use in place of soil) and fill in the whole garden, weather permitting.

Pretty much, these plants are planted properly but just with spaces in between each one. Didnt want to use my mulch yet since I still need to put more dirt in the entire bed. Right now, it looks like what I imagine groundhog mounds look like (I dont have that problem, so I dont know.???)

All this being said (& I apologize for it being so long) what do you guys think NOW?? Especially about putting the leaves down?

Gardengal...I'm really thinking about what your info said about how I won't see the effects until AFTER things start growing (or not growing). As it stands, the foliage is still alive and healthy. But I see what you mean about the root damage. It's like hitting your fingernail with a hammer. It looks fine until it starts to grow out and then it can be funky for 6 mos. to a year...ha ha ha.

    Bookmark   January 7, 2010 at 8:14PM
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mxk3(Zone 6 SE MI)

I overwinter for a couple reasons, the main one being I grow plants in decorative pots that are placed around the garden (mainly on the patios). So it's in the garage (or outside barricaded against the house) for the winter, out in the garden the rest of the year for these plants.

The other reason I overwinter is on occasion I have plants that I either haven't had a chance to plant yet or don't quite know what to do with yet (y'know - I saw it, I had to have it, now what do I do with it sort of thing).

As long as you get them dormant and KEEP them dormant until spring, they'll be fine, in my experience. Keep in mind that I am referring to zone-appropriate plants.

If you do a board search, you'll find other recent threads about this topic, also. :0)

    Bookmark   January 7, 2010 at 9:24PM
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brit5467(7b/8a Coastal VA)

Got 'cha!! I did the second one...."had to have it, don't know where to put it, etc."

Dormant -- that's the issue with our weather. Even tho they were clearance & some looked nearly dead, with our 70º weather last month, they got confused and all grew new growth. That's mainly what concerned me.

Actually, the Coral Bells & Guara never DID look dead & even with these freezes, they still looks like the day (err..month) I bought them, with the exception of a few lost leaves. But they ALL have new growth due to the weather, I'm sure.

And that's where I'm lost, I guess. I don't actually know what perennials are 'supposed' to look like this time of (our) year....dead, growing, stable or what.

At this point, the main ones are in the ground with a hope and a prayer for the Spring. At least I know I put an effort into trying to save them. If they don't make it or produce, then each one is nothing more than a few bucks lost. But you know how it IS.....they're LIVE enities and I want them to survive !!! :)

As far as the 'search'....I've tried that for so many things and always seem to end up with so many topics that don't seem to fit my question. I don't have time to go into each thread and read post after post, hoping to find what I'm looking for. Maybe I just don't know how to do it right. But, for instance, I'll type in something very specific and end up with "What kind of plants are YOU planting this Spring?" Doesn't seem relevant. Is it just me????

    Bookmark   January 7, 2010 at 9:55PM
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neverenoughflowers(6 SEPA Downingtown)

I have to agree with mxk3, I have overwintered many perennials in pots over the years and they have all turned out fine. If you were able to dig down to the roots in you flower beds, you would probably find that the ground is pretty frozen all the way down there too. I would put them in the empty raised bed, surround them with some mulch and let them get covered with snow. They should be fine in the spring to plant out. Carol

    Bookmark   January 7, 2010 at 10:32PM
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brit5467(7b/8a Coastal VA)

Tks I said, they're tucked in the best I could with soil around them all. I DID just go out and snug them up with some leaves as well. But I'm toast. Stick a fork in me. I'm having my dinner (finally) and going off to bed.

Tomorrow's another day, with buying MORE soil, mixing with compost, and planting the rest (which are more established and hopefully more hearty (although I snugged them up with leaves as well).

Thanks to all who walked me thru this whole ordeal !!!!!

    Bookmark   January 7, 2010 at 10:48PM
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diggerdee zone 6 CT

Count me in as someone who overwinters in pots all the time. My yearly plan is to get them inside the garage for the winter.

My plan doesn't always work out. This year it was warm for a bit later than usual and then wham! snow! So my pots were caught outside (they weren't dormant yet before the snow, which is why they were still outside). And there they still sit.

Would I have preferred to get them inside the garage? Yes.

Will I still attempt to bring them inside? Yes - to keep them at a more constant temp - when a day comes along where the weather is nice enough to do it!

Am I worried about them being outside? Not really. I might lose one or two or even more out of the couple hundred I have, but I've done this before and not had much of a problem.

Now, how zone affects this, I don't know. My first thought was that you are warmer, so if I can do it, you should be able to. But perhaps because you are warmer, your plants may not stay as consistently dormant as mine. I can't answer this question for you in your zone specifically - although it sounds like you've got most of them in the ground already anyway!

Good luck! You must be a hardy and hearty soul, lol, to be outside doing this at this time of year!


    Bookmark   January 8, 2010 at 5:43PM
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