It could be that your clematis are nutritionally deprived being in pots and small pots to boot. Watering them will quickly wash most nutrients out of the soil in the pots so you will need to add time released fertilizers to help combat the leaching effect.

If you want to keep them in pots, I would definitely go much bigger--in fact the bigger the better both for their survival in the heat of the summer but also the cold of the winter.

Does your garden soil drain well? If not digging a hole and overly amending it will just provide the plants with a swimming pool for their roots to drown in. If the soil drains reasonably well then you shouldn't have a problem. Planting them in a raised bed would aid immensely in drainage and overcome any drainage issues you might have with your soil.

Hey Lydia

You are the first person I've met on the forums that lives in JC,NJ. Welcome to the forum.

I grew up in JC a loong time ago, graduated from Snyder. My father has a super veggie garden in our back yard in the 1950s, long before most people even heard of organic gardening. He would take the wagon he made for me and some bushel baskets and collect fallen leaves in Audibon Park, and grind them up in a machine he made. Talk about garbage, every Sunday, on our way to my grandparents in Fort Lee, we would stop at the dumps in Secaucus, where Maxwell House dumped the coffee grounds so he could fill a few baskets to take home to add to the compost pile. We had beautiful earthworms, and he even overwintered some in a box in the cellar.

Unfortunately they were driven out in the mid seventies by vandals who also set fire to the house and I learned a few years ago from people on the high school forum that the property has been turned into a parking lot, which was sorely needed. But such a waste of the good soil underneath.

I'm glad to see you are trying to bring some beauty into the area.

Marie in ME

Thanks for your advice, nck. I will definitely put these in larger containers and report back - you've even got me thinking about building a raised bed! In case that doesn't work out, what size container would you recommend? I was looking on the container forum, and someone said that they had a clematis in a 20" pot and it was doing well.
Thanks for the welcome, Eden. Your dad's garden sounds like it was wonderful! Glad to meet a fellow Jersey girl!!

Generally speaking, the smallest size pot I have seen advised for a clematis is one that is 18 inches in height and depth. I would go for as large as you can find and afford. A cheaper alternative might be those huge black pots that you find at nurseries that sell trees. The bigger the pots the less watering you will do in the summer, the less likely the soil with freeze solid in the winter, and the happier the clematis.

One of our local nurseries has a "pot recycle" bin out front. They throw in empty plastic pots and you can just take what you need. I've picked up a few 5 gallon pots. Very cool!

Good catch Alice. That is exactly the type of pots that I am talking about. If price is a factor, you can't beat them.