overwinter clematis

bartelskateMay 20, 2005

I know it's a little early for me to be thinking about overwintering, but I have two giant (18 X 40) containers on my above-ground (5' approximately?) deck and I am planning to plant a clematis in each one. They both will be a 'Paul Farges' Summer Snow clematis which are hardy to zone 3 or zone 4 depending on which website you check. I am posting this because I have tried this before with two Henri clematis and they both died, but I don't think they are to blame. I'm just not sure how to take care of plants in pots over the winter. I won't be taking these containers inside because they are built into my deck and the vines will be gowing up a trellis that is also attached to the deck. I have been checking this forum and I see that I need to water the pots when they get dry, but I don't get it. Won't the water just freeze to a block of ice? Are you just watering when temperatures are above freezing? Are you watering every day? Every couple of weeks? When there is wet snow on the ground, are you still watering? And I have read that some people cover their plants so they don't get wet. These containers have drainage holes, will that suffice? Also, since these vines are supposedly hardy to zone 3, will I need to wrap my containers? I want to avoid that if possible because, well, the containers are pretty wooden boxes and that would look much nicer than burlap and newspaper. But I will wrap them if I have to, to keep them alive. And I am determined to keep these alive, so I would love to hear any advice you could give me.

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jenny_in_se_pa(USDA7 Sunset 32)

Alot of questions and I am not familiar with the clematises that you mention but there was a possibility that your Henryi didn't die. Sometimes young plants disappear the following season and may not emerge again for a year or even more - at least according to a number of people on the clematis forum.

For my own (a "Prince Charles" that is going into its 4th year for me), it is a group 3 so for winter, I leave the vines on its support and in late February, I'll go out and cut it back to the first couple pair of buds. Often the rest of the vine has some buds trying to swell during late winter warm spells, but I still cut the whole thing back because it will inevitably engulf the support by bloom time.

When/how often it is recommended to water during winter - that is mainly if it is dry (no rain or snow) and/or in my case where mine is on a covered balcony and happens to be against my bedroom wall and not along the rail to really get much natural water unless we have a Nor'easter (where I face NE and get the full brunt of those windy wet Atlantic coastal storms). One would water when the soil was dry and the temps were well above freezing - ie., in the 40° Fs or higher. In general, plants need less water during the winter when dormant, but they do appreciate some for their roots as the roots continue to grow in winter when the soil is not frozen.

Yes, the containers can often freeze, but the bigger it is, the longer it would take to do so. For hardy perennials, this isn't so much of a problem as a detrimental cycle of freeze/thaw, which can burst the roots. So once it's frozen, it should hopefully stay that way and graduallly thaw. If you get snow, then that is a good insulator and you can put some mulch on top (I use pine needles on my clematis).

Only thing you can do is try. You might have a mild winter that will allow a young plant to establish a more mature root system and gradually gain its fully hardiness in a container. I am finding that this is often the case with plants - they need time to gain that hardiness (even if planted in the ground and moreso in a container).

The one other thing to look out for is the phenomena where containers often heat up faster than the ground, so sometimes this triggers your plants to wake up a little earlier than they should and then along comes a frost or freeze. Clematis buds are somewhat sensitive to sudden freezes if they are swollen or leafing.

This was my clematis at the end of last June:

The ridiculous below-normal temps makes me think it ain't gonna be ready to bloom earlier than normal like it did last year! Especially since it looked like this on 5/23/04:

- and the stems are barely 2ft or so tall right now:

    Bookmark   May 20, 2005 at 6:31PM
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Since you live in Iowa and have snow on the ground most of the winter, I wouldn't worry too much about watering. As Jenny says, water only when temps are above 40 and the soil is dry. I have three clematises, two are jackmaniis and the third is a Sunset. I just planted the Sunset this year so can't say anything about it. I do know that the jackmanii I bought three years ago as a larger plant is doing fabulously well, but the smaller plant bought the following year is promising to do well too. The larger plant is huge right now, no buds. The smaller one is considerably smaller, partly due to the fact that I managed to snap off the growing tip when it just started to grow well this year. I mulch them both heavily over the winter because I don't have any snow cover and it does get quite cold here. It also dries out during the winter so I water about once a month. Our temps fluctuate greatly during the winter - 65 one day 17 the next. But I've never had roots burst as Jenny describes. I think the mulch and the large size of the pots keeps that from happening. I think you'll be okay, since the zone for your clematis is at least a 4, if not a 3. Mulch heavily with whatever you use in Iowa. I use pine bark chips.

Also like Jenny I prune heavily in the spring, about February 15th here, maybe March 1st where you are.

I had a clematis terniflora a few years ago that did beautifully, but it grew too big to really enjoy on my small balcony. That's when I planted the jackmanii and I moved it from the balcony railing back up against the wall where it appears to be right in its element. It flowered heavily last year, and I expect better this year because it's a much stronger vine this year.

One other thing, I'm trying something new this year with all my plants, and so far either I'm turning into the best gardener around or this product really works. It's called Messenger, and you can order either in large or small applications. You can read about it and order it at www.edenbio.com.

    Bookmark   May 25, 2005 at 11:59PM
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Just wanted to thank you both for your comments. Both of your vines look amazing! This fall I will take extra precautions and mulch heavily. Last time, I didn't do that and also didn't know that I should water when temperatures are above freezing, so hopefully they will have a better chance of making it. If these don't survive, I'm sure I will be bull-headed and try again next spring. :)

    Bookmark   June 2, 2005 at 10:04AM
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LindaMA(MA z5)

Jenny and Posegirl, your Clematis' look great, you both give me a lot of hope regarding my 3. So far I have a Blue Bird, Cezanne and The President. I may have to give the Blue Bird away because of the rate it's growing. It's taking over the wall on my deck and it's only June!

    Bookmark   June 16, 2005 at 9:45AM
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I'm having the same problem this year with all my clematises. They're way too big to be supported by what I had up last year. I'm going to have to come up with something to hold the weight of the vines. I thought I might put wrought iron shelf holders and they lay a 2' piece of latice on top of the shelves above my balcony door. I'll fasten the latice and when the clematis gets big enough I can lay it on the lattice. Does that sound like a good idea?

    Bookmark   June 17, 2005 at 12:55AM
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