I prefer not planting anything in a pot that will compete with the clematis for water. Just means you will have to water that more frequently. If you don't mind, then I don't see any issues with doing so as long as it is something that doesn't have a rather extensive root system. The pot will need to be large for any clematis to begin with and something else that develops a large root system is going to quickly fill the pot with roots.

I have 3 containers using creeping jenny. It hangs over the sides to about 12-14". This ground cover is yellow which looks great with blues and purples. I have it with pink as well. You would not think that this combination would work but it does. It does not have a deep root system and covers the entire planter quickly. I bought a small pot and divided it into 3 sections. In no time it will spread and it is a perennial. I also have containers with petunias. They too spread quickly and are still making it in this incredible heat. I don't mind watering Miguel. It gives the pots a finished look.

Robin, I grow the chartreuse creeping jenny also, just not in pots with clematis. Be careful where it gets as it spreads like wildfire when it gets established. It might look dead if it gets superdry but once it rains again, it is back with a vengance.

I came up with one more ground cover suggestion. There are numerous varities of thyme that range from short short to several inches. I have them all over my gardens. I'll bet that they would look great in the container with the clems. They also have an additional perk and that is a lovely scent. What a good idea, think I will try it next year. I know tht it works with my garden clems.

Violetta, I highly recommend Sedum Album for using in your pot. I use Album 'Balticum' as a living mulch for my potted clematis, roses & daylilies and they all seem to love it!
Here's a clickable thumbnail of a daylily pot:
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~ marea

I would have thought that sedums and thymes wouldn't like all the water that clematis would require. I know that both of those types of plants are doing well in my garden in the drought we are experiencing and I don't water them at all.

I did put some groundcovers on the outer ridge of some tubs that had a clem in the inner pot. Seemed to work out ok. But I am concerned that the roots of a groundcover, even if shallow, might impede new shoots from coming up, unless it is separated from the clem roots. This is a problem for me, as most of the aboveground stems & foliage dies back to nubs when our Winters are harsh & windy. Especially on young plants, which most of mine are.

I don't know if the vinca in the pot with Star of India did cause any problems, but altho it has a few roots that have not rotted, nothing has come to the surface, even tho I moved it out & repotted it.

I think low annuals would be a better choice for me.

Marie in ME

Marea, the sedum are lovely. There are so many beautiful plants that you could put with the clems. Miguel is right thyme and sedum like dry soil, however, I have it at the base of my clems and they do not seem to object. I tend to prefer accompanying plants that spill over the sides of the pots. I wish that I knew how to post photos so that you could see just how lovely the creeping jenney looks. It does spread quickly . Next season I will have enough spares from the overages that I will have more for some other clems. Love the idea of the vinca. Will try that one next season. Hi Miguel.

Hi Robin. Watch out for that creeping jenny. I spent a summer trying to eradicate it from an area in the back yard. I still have it in one bed that is bound on three sides by a patio and gravel area and one side by the yard. I have to continually pull it out of the grass or it would take over. Love the color though!

Miguel, I live in zone 6 and it is not as agressive. Love how the color changes. It ranges from a bright green to yellow. The color variations in the pot are just lovely. It gives a layered effect with these wonderful variations. If they start to take over I just pull them out and plant them in another pot. I wish I know how to post to show you.

Robin, this may help you post a photo:

http://forums.gardenweb.com/forums/load/afrviolet/msg0819243330083.html?7

I have creeping jenny in with my Piilu. This is the third year for the two together. This last year the Piilu died all the way back, as we'd moved to Colorado and I left it outside in a sheltered, but sunny spot. Since the jenny died back as well it didn't seem to impede the new shoots coming up.

Robin I really like the affect too. Only wish that the soil level was a little higher in the pot so that more cascaded over the sides.