Using A Heating Cable For Potted Plants During Winter

menashe79September 4, 2012

Hey folks,

I want to plant a tall lilac bush and a tall service berry bush (looking for 10' tall or so). But, the area that it's going in is on top of my stone patio. So, I want to keep them in a large insulated container or build a raised bed with insulation. I live in MA though and fear they might die during the winter due to the roots freezing. I'm wondering if I put a soil heating cable into the soil of the insulated pot/raised bed if that would suffice to ensure they survive the winters? Maybe also a soil heating mat and some extra mulch on top for good measure?

What do you think?

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laurell(8 - Washington)

Iirc, lilacs require a good strong chill to bloom. Are your winters so cold that something that goes dormant like a lilac can't survive?

    Bookmark   September 5, 2012 at 12:58AM
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I know very little about plant care, so I just assumed it couldn't make it through freezing temperatures and/or snow if it was potted. But if you think it can, that's great! What about ServiceBerry's?


    Bookmark   September 5, 2012 at 8:57AM
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karin_mt(4 MT)

Serviceberries are really hardy, all the way up to zone 3, so I think they would be fine. Snow cover would be beneficial because it would insulate the containers from temperature swings.

Wintering plants in containers or raised beds does expose the roots to bigger temperature swings than being in the ground - there's no way around that. But both these plants are tough and probably worth a shot.

I would not recommend the soil heating cables or mats because that would actually be quite warm and seems more likely to cause damage. Besides, do you really want to use that much energy? (~20 watts each x 24 hours a day x all winter long) Granted, it's not a huge use of energy but it seems a little gratuitous. Then again, I am more sensitive than most about energy use. :)

Anyway, I would try it without heat and if possible you can shovel snow over the pots to keep them insulated. That's what I do with my marginally hardy roses, which are handily planted right next to the sidewalk which needs frequent shoveling.

Oh - also make sure the containers are capable of handling the freeze-thaw. Definitely watch out for ceramic containers.

    Bookmark   September 5, 2012 at 10:24AM
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It's not that there isn't scientific inquiry into freeze tolerance of container trees. But this type of information can be obscurely located, difficult to access and probably won't be specifically about the plants you're interested in. And much in horticulture is not known. On top of that, there are micro-climate influences that can be significant variables in the success or failure of such an experiment. You will probably need to pay your money and take your chances.

Since freezing and staying frozen is probably much better for a plant than freeze-thaw-freeze-thaw, etc... a well insulated container sounds like a good idea. Not really trying to discourage your experimentation with the heat cable, but I doubt it will be an advantage more than choosing plants (which you've already done) whose roots are capable of tolerating freeze, since that's what happens in the ground where they live. In order to minimize freeze-thaw cycles, it would be good to keep the plant in a location where the sun does not hit it once it's frozen. Reporting back on the results of your experiment, with details, might be helpful for others in the future.

    Bookmark   September 5, 2012 at 10:35AM
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Ok, cool! I'll give it a shot without the the cables. Hope it works because the plants I'm buying are tall so they are between $130 and $195 each (ouch).

Do you guys have any other suggestions for tall shrubs (around 10' or greater) that could survive in a container/raised bed through winter? I've got a 6' fence that doesn't quite block out the neighbor's windows. I wanted to do trees, but I read such mixed things about the trees ability to survive under these conditions.


    Bookmark   September 5, 2012 at 11:21AM
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Question - are you talking about surviving being containerized for just this one winter or forever? No space to actually plant in the ground?

    Bookmark   September 5, 2012 at 12:29PM
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Yeah, forever. That would be it's permanent location.

    Bookmark   September 5, 2012 at 2:15PM
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Have you ever grown trees in containers long term? It's not exactly a plant-and-forget proposition. Attention must be paid to watering and fertilizing - much more so than any inground plantings - and the trees will need to be lifted, root pruned and repotted with fresh medium from time to time. The bigger the tree, the more work that will be.

In general, the recommendation is to look for a plant at least two zones lower than your hardiness zone - if you are in zone 6, you should be looking at plants with a zone 4 hardiness rating. That is not always a guarantee the plant will survive - roots are the most vulnerable to cold of any woody plant part and container soils can freeze easily, as can those in a raised bed or any other elevated situation that lacks the insulating effect of a large soil mass.

FWIW, I think it would be easier to insulate a container than it would a raised bed. Bubble wrap is a good choice, but burlap (wrapped in layers) and newspapers work well also. I agree the heating cable may be excessive - you want the soil to stay cold but keep from freezing solid.

Personally, I would not risk the expense and the size of the trees you propose for this somewhat uncertain enterprise. I'd be much more inclined to experiment with something much smaller and cheaper first and see how it goes before committing to big plants and big bucks. btw, smaller plants initially generally fair better at this sort of activity anyway.

    Bookmark   September 5, 2012 at 5:14PM
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I did not know all of that regarding the maintenance. Thanks for the heads up. Yeah...I've got no interest in doing that, so trees are definitely out.

Would you agree that the lilacs and service berry's wouldn't be as sensitive as trees would be (or require pruning the roots, etc)?

    Bookmark   September 5, 2012 at 5:18PM
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mad_gallica(zone 5 - eastern New York)

A large lilac in a pot would be a lot like an elephant in an apartment.

Anything that big in a pot is going to have issues.

    Bookmark   September 5, 2012 at 5:23PM
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Hmmm...Well, what's the root system like of lilacs and service berrys? Are they strong bark like structures, similar to trees? Or are they thinner and softer? Because I could plant them above the pvc pool pipes, I'm just afraid they'll damage the pipes as they grow. What do you think?

    Bookmark   September 5, 2012 at 5:31PM
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Serviceberries ARE trees, just smallish deciduous ones, but they will still have a large, spreading root systems. Ditto the lilacs. Lilacs are actually included in a classification known as suckering shrubs, which describes their habit of generating new stem growth from the base of the plant (root crown). Eventually they can form an impressively large colony. And either plant could be an issue when planted directly above shallow pool piping

Let's go back to the beginning. What exactly were you hoping to accomplish by these planted containers or raised beds? Privacy? Some softening greenery? Seasonal color? Cuz there are numerous ways of accomplishing these goals without having to go to extremes.

    Bookmark   September 5, 2012 at 6:28PM
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nullqwerty, as gardengal points out, it can be some doing to keep a large plant going in a container for the long haul. Still, it is done here and there with some success. You might consider showing the forum what the actual problem is in a photo. We might be able to suggest a workable solution that you have not yet thought of... maybe one that is easier, cheaper, or less risky.

To answer your question about what plants might survive a container through the winter, I have a vague recollection from my days in Illinois of Japanese Maple being one that did this with little or no complaining. It's too long ago so I can't speak to details of it. Making a guess, I'd bet that Burning Bush also could. As probably could the one's you've mentioned. Actually, the soil and roots freeze--in the ground and in the container--and plants that live in harsh winters are used to this. They're not used to repeated freezes & thaws. Depending on your container, you'd need insulation that cushions as the icy rootball can break the container if something doesn't give. A complete perimeter styrafoam lining of the container would be my first choice. I've seen it used this way. You might consider x-posting your question in a state forum with a large, cold city. I know that there are many container trees in Chicago. In places like that, people would know more about this subject.

    Bookmark   September 5, 2012 at 9:34PM
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@gardengal48 : Yep, for privacy. I've got a 6' fence, but right above it are neighbors windows that I was hoping to block out as best as I could. So, I need something tall. I'm just really out of ideas, since I can't plant anything due to the pool pipes, and not much else could fit there either (like no spot for a shed) since the fence is only 7-8 feet from the pool and runs parallel to it. Only other thing I was thinking of was maybe a trellis with climbing rose bushes or something.

@Yardvaark : Thanks for all tips. I'd post a pic, but just in case my neighbor comes across this in the future, I figure I better not. Again though, thanks for the help.

Seems like the general consensus is that most feel with a well insulated container or raised bed, a lilac or serviceberry should survive. So, I'll probably give that a shot.

Again, thanks everyone

    Bookmark   September 5, 2012 at 9:58PM
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OK, now that I've got an idea what you are going for.......:-)

FWIW, neither the lilac or serviceberry are very effective privacy plants. Better in summer than winter but not ideal even in the height of the season. Nice flowers.......crummy screening ability. One suggestion would be a raised bed with clumping bamboo. Bamboo is an excellent screening plant, as it is pretty much evergreen, will become quite dense in time, has a very narrow profile and can generate some pretty fast height. And because bamboo is just a big ornamental grass, it does not have a deep root system, like the trees/shrubs would. And clumping bamboo - is its name implies - does not develop a very widely spreading root system, either.

I'd look at the Fargesia selections. These are all extremely well-behaved clumpers and some of the most cold tolerant of any bamboo species (-20F, including root hardiness). If you can construct a reasonably deep raised bed (12-18" deep), you should be good to go with these :-)

    Bookmark   September 7, 2012 at 3:34PM
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You are awesome! Thank you so much! I have never heard of clumping bamboo but it looks like it would be great for my situation. And being near a pool I think it has a really nice look. Thank you!!!!

    Bookmark   September 7, 2012 at 4:41PM
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Do the Fargesia varieties turn yellow and drop leaves at some point during the year? Could be problematic dropping into the pool or neighbor's yard.

    Bookmark   September 7, 2012 at 5:19PM
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I think I'd be ok with that if they did. It seems to be the best solution so far.

    Bookmark   September 7, 2012 at 5:50PM
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I have been a bamboo lover for a long time. I've owned running bamboo but always liked the idea of clumping bamboo, thinking it sounded like a winning solution. But after moving to Florida and seeing what clumping bamboo really becomes, I've changed my opinion of it. I'm not saying don't get clumping bamboo, but know and understand what it is you're getting beforehand as clumpers can become monsters, too. A neighbor of mine has some that he would dearly love to get rid of but can't afford the expense as it would require a D-9 CAT. An army could not work its way through it. Also, bamboo tends to shed a lot. The site I've linked below has a lot of good information about bamboo.

Here is a link that might be useful: Lewis Bamboo

    Bookmark   September 8, 2012 at 11:24AM
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Clumping bamboo in MA will not be the same as clumping bamboo in FL :-) Even in my pretty mild climate, clumping bamboo is an extremely manageable plant and I see no reason not assume a similar well-behaved habit in colder zones.

From a regional bamboo specialty nursery:
Overview of Clumping Bamboo

Clumping bamboo are defined as having a non-invasive rhizome structure (known as pachymorph rhizome) which differs from the better known �and sometimes feared�running bamboo (leptomorph rhizome). Clumpers form a tight cluster of gently arching culms extending from a relatively small root mass. Each underground bud pushes upward forming culms, and do not become long running rhizomes. Instead, clumping bamboos grow outward in a circular formation at a modest pace of 2 to 12 inches per year. Canopy growth is also relatively slow, usually gaining a couple feet of height and width annually. Height range at maturity is between 10 and 20 feet for most species. There are some exceptions; tropical and subtropical species can reach 50 feet or more in the US, given hot, southern climates.

We have a special affection for hardy clumping bamboos. We believe these plants will help overcome popular fears about bamboo, and pave the way to its acceptance as a significant addition to the landscape as well as its incorporation into our culture. Bamboo Garden is on the forefront of introducing new and exciting species of clumping bamboo into the United States and promoting their multitude of uses. Though many are new to cultivation, clumping bamboo are gaining recognition for their landscape value as low maintenance alternatives to the larger, more vigorous, running bamboos. Fargesia sp. �Rufa�, with plumes of feather-like foliage, provide a wonderful accent to the small urban garden. Larger species, such as F. robusta, create dense evergreen privacy screens to over 15 feet. The gracefully weeping culms of Borinda angustissima and F. sp. �Jiuzhaigou� support masses of tiny leaves with a delicate, airy texture. Outer culms can be topped to make the plant more compact and upright. New introduction, F. sp. �Scabrida�, has outstanding colors: purple culms outlined by rusty-red culm sheaths contrasting with dark green leaves. Some species, such as F. nitida, are among the most cold hardy bamboo, surviving temperatures as low as negative 20� Fahrenheit.

Most thrive in a partial shade environment, but there is enough variety to find a suitable clumping bamboo for just about any need. Our selection have special significance and unique qualities for the home garden or commercial landscape. We hope the pages of our website offer a new perspective of the possibilities and wonderful variety among clumping bamboo.

Here is a link that might be useful: Bamboo Gardens

    Bookmark   September 9, 2012 at 4:16PM
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Gardengal, re: the bamboo, it might be the regional difference or it might be that some of the clumps I've seen have been "let go" until they became unmanageable. I don't want to discourage anyone from liking or using bamboo. I'm just warning watch out, IN CASE it applies, though not sure it would here. Some of the clumping bamboos I've seen no light passes through. It's pitch black in there. I've even tried to cut some canes out of my neighbor's to build some things, but it's too much work. You can't even take the cane you want. You must take the most outside one and some of those are tough to yank out of the canopy. They're 50' tall, but the OP probably would use a shorter variety. Many variables here.

    Bookmark   September 10, 2012 at 8:59PM
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mad_gallica(zone 5 - eastern New York)

Biggest variable is going to be what survives. Given the cost of bamboo, I'd definitely ask in the Bamboo forum about people's experiences before getting in to this at all deep. Even the hardiest bamboo take a significant hit here when it gets cold, and those have the insulation benefit of being in the ground.

    Bookmark   September 10, 2012 at 9:34PM
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