Jennie, all zone 5 gardeners do not have the same conditions so it is going to be very difficult to say whether your clematis will survive in the pot over the winter, whether it may just die back to the soil level each year, or whether it will do fine. Your own xperience is going to be your best advice.

For future reference though, most clematis will do better in the ground since the ground will insulate the roots, in addition to any mulch you may supply, better than anything else you can apply. Why not plant the clematis in the ground behind the pot and reserve the pot for annuals?

f you do plant clematis in pots, make sure you have the biggest pot possible since the bigger the pot, the more soil it will hold and the more insulating power you will have. You say the pot is fairly large but what does that mean in terms of height, depth, and width? Secondly, in colder zones, I would plant type IIIs in pots since type IIIs bloom on old wood. You will trim the type IIIs back each year so it won't matter if the top growth dies back or not. In the case of the type IIs, if it dies back to the ground, either the plant will flower much later in the season than it normally would (not necessarily a bad thing) or it may not flower at all if it only blooms on old wood.

I tried planting some of my clems in large pots last Fall, where the ground was too rocky or too close to the old lilac clump I wanted them to climb.For example, I had a Polish Spirit planted too close to the lilacs & it never bloomed in the 4 or 5 years it was planted from a tiny pot.It did have stronger foliage last year & climbed more, but still no flowers. I dug it up & put in a large pot/tub with a Dorota and an gallon pot of Dr Ruppel. PS was one of my first potted ones to be up & running, & has buds now.

I put rocks in the bottom of the tubs & filled them to the brim, and a little mounded on top, with soil so water wouln't accumulate when the snow melted. Then I put 3 ft wire fencing around the pots or groups of pots & filled in the space around the tubs with fallen tree leaves. I put some cardboard boxes on top of the leaves on the surface to absorb some excess moisture from snow melt.

Unfortunately, on a nice early Spring day I removed the fences, leaves & cardboard. Then we had 2 of the worse snowstorms of the Winter in April.

Another mistake I made was to use straight garden soil for the top layer. I didn't realize how much clay was in my soil. I first scratched the clay a bit when nothing started coming up in some pots & some dug into the ground in smaller pots. This helped a few break through. Then a few days later I dug a little deeper and removed the clay from the surface, at least in the area where a nub of a stem remained. Found a few more live ones.

Yesterday & today I have been digging deeper and have found some life but also a few rotted roots. In both the above and under ground places. On a few I dug as far as I dared and will just have to wait and see.

This Fall I plan on doing things pretty much the same, but will mix lots of compost or leaf mold in with the top covering soil. And maybe put some plastic over the pots in the locations where I had some rotten roots. And wait a little longer to uncover. Just get so anxious for them to start growing that I probably jumped the gun.

Marie in ME

I would never use garden soil in pots. I would use a premium potting soil instead. No matter what I'm growing in pots with the exception of waterlilies.

Even if you have fabulous garden soil, putting it in a pot changes it's structure. It will never drain as well as it should.

This is probably the reason for the rotted roots.

Pots with drainage holes don't really need rocks in the bottom either.

Being too close to a lilac should not have hurt the Polish Spirit. I've got Clems practically on top of other plants, including roses and lilacs with no loss of bloom. I do make sure they are watered in summer though and do fertilize them too. None of my 40 + Clems has root space to itself, they are all within 12"-24" of another plant.

Of course, too much shade could be a factor in lack of bloom.

I think PS was getting enough sun. It was, and still is, on the North side of the 5x6 foot old lilac clump, about 6 feet from the edge of the road so gets afternoon sun.There is a Marie Boisselot that I have had for about the same length of time, but it was a gallon or more size when I planted it, insted of the then tiny PS, at the same distance from the road. But it was planted on the other side of the gate, about 3 feet from the lilacs. It climbs up a pole before reaching the lilac branches above the gate, and keeps going up for about 10 feet. With it's very large flat white flowers it is quite impressive.

Even tho I did not know about the proper care & feeding of clems at the time, and am still learning, I have never had one bit of trouble with Marie. I don't think that being close to roses & some other shrubs would be so harmful to a clem as close proximity to the roots of very large, old & well established shrub. To me it seems a bit like planting too close to a well established tree.

I haven't had any trouble planting bulbous lilies, daylilies hosta & other plants that used to be my favorites in pots with compost or leaf mold in the bottom and regular soil on top, except that I do remember in the past I usually mixed the garden soil with potting mix that other plant were bought with, and last Fall I was in such a rush that I had neglected to mix anything with it, just filled pots with soil I had dug to make a hole for another pot of clems.

Some of my worst cases of root rot in the past were in plants from a local nursery that used a pro mix for potting everything. They also had a plastic plug in the center hole of the pot. Not sure if it was the mix or the plug that caused them to retain too much water, So the next year that bought clems from them, I repotted in a slightly larger pot asap. But I noticed today that the one carousel I found with rotten roots was one that I had forgotten to repot.

The rocks in the bottom are for a little more insurance. There is no scarcity of them here in New England. I didn't always remember to put rocks in the bottom of the pots or the tubs, and they may have been the ones that did rot. I haven't dug all the way down in all of the pots yet. In some tubs, one clem would rot, and the other 1 or 2 would not. ???

All in all, I did lose much fewer this year than in the previous years. And there probably was more snow in April 07 than in the last 2 Winters combined.

Even with all the good advice on the forums, I guess I still do a lot of learning by trial & error.

Marie in ME

I agreee with BorS, garden soil should not be used for pots. Good potting mixture is what should be used to allow for adequate drainage.