A few years ago I decided to try growing some Henryi clematis into our Chinese wisteria 'tree' to provide some floral interest after the wisteria spring flush of flowers finishes and before the secondary summer bloom of the wisteria. Until this year the clematis has only produced a few flowers - I doubt the clematis will ever produce an overwhelming show but this is the first year that it has produced more than just a couple of flowers in the upper part of the 'tree'.

The flowers are most easily visible at the base of the 'tree' but are also now scattered throughout the top too.
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A closer view of some in the top - it's too bad that the rachis of the wisteria flowers (the central stem of the flowers) hasn't dropped off yet so it's a bit messy-looking!
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A Piilu clematis growing into a hydrangea near the south side of the wisteria appears to be testing out the wisteria as additional territory for it to colonize:
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So, while it's taken a few years for the Henryi clematis to bulk up in the wisteria, I'm quite happy with it and am looking forward to potentially a bigger show from the clematis in the future as it continues to mature and colonize its wisteria companion.