Here's a close-up of the flowers of this variety in bloom,
and here's a picture of the vine itself.
It's known as the chocolate vine (flowers are more often dark purple than white) and the five-leaf akebia. Everything I read about it sounds wonderful, except for its potential invasiveness. Sigh. Here's what the National Park Service has to say:
Fiveleaf akebia is a vigorous vine that grows as a groundcover and climbs shrubs and trees by twining. Once established, its dense growth crowds out native plants...
They go on to suggest that
In the eastern U.S., some great native vines that are available as substitutes for Akebia including [sic] trumpet honeysuckle (Lonicera sempervirens), trumpet creeper (Campsis radicans), Virginia creeper (Parthenocissus quinquefolia), cross vine (Bignonia capreolata), and Dutchman’s pipe (Aristolochia durior).
I hardly need to train Virginia creeper up the trellis, it is happily romping among the compost piles!
I am not discouraged, though, since it seems easy to keep in bounds, especially where I am planning to plant it. Stay tuned...