I grow a 'Montana' variety of clematis against the south side of our house. It blooms profusely every spring, as long as I am diligent about cutting it back right after it blooms (some clematis bloom on the previous years' growth, like this one). The problem with that is the plant looks quite denuded and yucky in early summer, and it also leaves this side of the house showing, which badly needs a paint job. I've long wanted some other climbing vine to grow in tandem with the clematis, blooming in late summer so that the whole area looks nice all year. I've tried several things to no avail, but this year I've had a success story.
Most of the green growth above is the clematis vine, in the form of pointed arrow-shaped leaves. This June I seeded some purple hyacinth beans below it, and that's what you see growing up and through, and blooming now. I expect this plant to keep growing, and bloom until our first frost, which isn't usually until mid-December. I'll let the seeds mature on the plant, with the hopes that it will re-seed itself (it's an annual vine) and do the same thing next year, although with earlier timing, filling in just as I cut back the clematis in June.
I bought these seeds from Renee's, though you can also find them at Baker Creek. The purple seedpods are lovely, as are the deep red stems. The young leaves on this plant are apparently edible (so it might make a nice summer alternative to spinach), but only cooked, and so are the pods, though only when immature and again, only when cooked. They contain a cyanide compound that is poisonous and can be quite dangerous when eaten raw. So, eat the leaves and pods quite young and quite cooked. There is some debate about the older seeds/pods, so I would stay away from those altogether.
Apparently Thomas Jefferson planted this vine at Monticello, so it has a long history, but I don't think I've seen it being grown before. Perhaps it's more common on the East Coast.
The leaves are gorgeous too, heart-shaped with red veins.
So, if you need a fast-growing summer vine with beautiful flowers and seeds, and one that is also edible, this would be a good choice. I'm quite happy to find a companion plant for the clematis, and this plant has the added benefit of having the ability (like all peas and beans) to fix nitrogen in the soil.