Eks, it is generally not a good idea to mix clematis types. This is due to the different ways the different groups are pruned. All that being said, I do have a type II and type I clematis planted together (macropetala and Belle of Woking). Types one and two generally don't get pruned at all except to contain their size and to remove deadwood. That is the reason that I mixed those two types.

Most people would agree that planting type IIIs with type Is and the IIs is not a good idea since type IIIs get pruned back severely in the winter or early spring. Trying to selectively prune a type III intermixed with a type I or II is going to be difficult to do. That being said no one says you have to prune type IIIs at all. I have seen pictures of a Polish Spirit climbing a tall tree in one of my clematis books (I believe it was Linda Buetler's book "Gardening with Clematis"). The drawback to not pruning a type III clematis is that it can get very tall and leggy, the blooms may be at the top of the plant instead of lower down on the vines, and the lower leaves may yellow and fall off. So in summation, can you interplant the three? Yes, you can if you can live with the aforementioned things happening or if you have the patience of Job when you do your pruning or even if every couple of years, you trim all the clematis vines back and are willing to take the risk of having a year when your type I and II clematis do not bloom.

Bottom line, I wouldn't do it but then it is your decision to make. You alone know what you can live with and what you can't better than anyone else!

eks,

Im not sure what you mean by mixing. You certainly could alternate type IIs and IIIs around the gazebo, (say at each post) as long as the base of the plants were separated enough to allow pruning of the type IIIs. There could some intermingling as the ends of the branches come together which should not cause a lot of trouble when pruning.

Hal

Another idea common with clematis enthusiasts..... mix a climbing rose with a clematis (non pruning clem types easiest). A classic combo for a gazebo...

Hal

Frankly, it depends on the zone you live in. The pruning techniques have been greatly overrated, I live in a zone where winter damage occurs and the best advice I got is not to bother with the specific pruning but cut off in spring whatever appears to be dead (watch out for new shoots on teh old wood). This has worked just perfect, I prune end of April or beggining of May, therefore I mix different types, no problem. It looks like you are in similar zone to mine.

If you are planting your clematis within 5-6 feet of each-other then I can assure you, you will be sorry for mixing types as the plants mature,.... I know, I've done this. The plants get very large as they mature and it is near to impossible to decide which is which in the tangled mess of vines. I no longer mix the group 2's with the group 3's. I learned the hard way. Group 3's are far more vigorous and there are so many of them to choose from. If you want an almost instant cover, then I suggest all group 3's. It's easy and they're a spectular vine, far outperforming in size.
Suzy

Thank you everyone for the responses. I'll probably try to keep my types on opposite sides of the gazebo. I'd love the idea of a climbing rose/clematis combo. Climbing roses can be a bit of a challenge in zone 5. If anyone has any rose/clematis combos that do well in zone 5, I'd love to know about them. My color scheme pinks/blues/whites/purples.

Thanks!