I have tried this with several shrubs and IME, the stiffer the branches, the better. I also like relatively long internodes (space between leaves on the stem) so that the clematis doesn't smother the bush it's growing on.

I have C. 'Geurnsey Cream' in a late-blooming lilac, Syringa x prestoniae 'Donald Wyman' that works OK, but I wish I had planted it on the sunny side of the bush since currently it grows mostly into the bush's interior and it isn't easy to see the blossoms. It was also the first one I tried, and I didn't realize how wide the lilac would get when I placed the clematis and wish I had placed it a bit further out.
{{gwi:197157}}From clematis

Clematis 'Venosa Violacea' grows into this pagoda dogwood (Cornus alternifolia), but the voles keep eating both their roots, so it hasn't been as successful as it might have been.
{{gwi:592631}}From clematis

Hydrangea macrophylla 'Endless Summer' hosts C. Ville de Lyon, which is relatively large and so starts in ES and then rambles up to a porch railing. This photo was taken in its second or third year, and now that the hydrangea has grown into my native soil, it's blue, but it still looks nice.
{{gwi:592633}}From clematis

I think my most successful is two clematis that I have growing into is a Hydrangea paniculata 'Quick Fire.' This one is 'Little Bas.'
{{gwi:248944}}From clematis on hydrangea July 9, 2013

{{gwi:592636}}From clematis

and I don't remember which one this is, but it is on another side of the same shrub, and blooms just a bit later.
{{gwi:592638}}From clematis

C. 'Betty Corning' and 'Viola' and at least one other grow into a spice bush here (Lindera benzoin) but this hasn't been as successful as I would have liked since the new growth on the spicebush is quite floppy and so the shrub gets pulled out of shape and just looks sloppy.
{{gwi:592640}}From June 22, 2013

Here's a first year C. 'Fascination' in 'Sunkist' arboritae. I like the color combination, but I am not sure how it will do in the long run.
{{gwi:592643}}From clematis

This C. pitcheri hybrid starts up the tomato cage, but then wanders into the deciduous holly, Ilex verticillata 'Winter Red' in front of it and the 'Fat Albert' blue spruce behind it. Several of my clematis that were planted after the shrub was good sized are planted a bit away from the shrub so they could get a good start, and so start up another support and then move into the shrub.
{{gwi:592644}}From clematis

Sadly, I haven't had as good of luck. Instead of rambling through and coexisting happily I've had several Clematis smother and kill shrubs...I had planted integrifolias throughout my shrub/tree/perennial beds and while some have done well, Alionushka in particular has been a huge fat smothering monster and Petite Faucon has as well.

Two I planted on neighbor's boxwood hedge have died out. It is either feast or famine for me

nhbabs,

Thank you very much for taking the time with this detailed account.

We're thinking along the same lines. I have a successful pairing with my Agnes rugosa and Huldine, and a couple of others. I'm wondering now if a h. paniculata standard could play host to a clematis or two. Your post has given me other ideas; much to think about.

BoS, I appreciate you input as well (and as usual).

Gary

My personal favorite is a purple leaf smoke bush, especially with a soft pink flowered clem (I used Nelly Moser). I had clematis growing through all manner of shrubs and trees in my old garden as there simply were not enough other supports available - no shrubs were damaged or harmed during this exercise :-)) 'Mrs. Bateman' on a Cotoneaster bullyana, 'Gypsy Queen' on Pittosporum garnetii, tangutica in my apple tree, montana through the lilac, 'Mme Julia Correvon' through the Rosa glauca. It all works!

Ah, great to mention of Rosa glauca (I'm old enough to call it rubrifolia, but love it by whatever name). Great suggestions, not all possible in my zone. I'm fairly sure I lost one of my smoke bushes in this wicked, awful winter. But what a terrific idea, perhaps even rambling through the dead, but definitely "airy and loose," branching.

Gary

I'm with BorS. My clems have generally hurt the shrubs I've grown them on by shading out the shrub underneath. I prefer growing them on objects now, except for 2 I have growing on a very large forsythia. They don't seem to hurt that at all.

Polish Spirit is supposed to be up in the crabapple but instead flops in a huge mass around the trunk. Putting two Rhododendrons and several huecheras and lilies at risk.