i tried to find a picture of one in bloom but haven't come across it yet. i have some in my collection but not posted. they can grow quite a bit quickly as an example here are some pictures including them (the trellis in the upper left to the back which isn't flowering as they flowered late in the fall). by the time they flowered they'd be overtopping the trellis and look like a big white fuzzy mushroom with all the blooms:
May 5
they were trimmed back in the early spring if there was anything left from the deer chomping them. sometimes the deer would eat everything in between they could reach and then the top stuff we'd have to pull off the trellis. other times the rabbits would eat all the lower stuff right down to the ground. in the really hard winters they'd dig down further and get whatever they could and also were eating things like the bark from the poison sumac and cedar trees. hard to imagine wanting to eat that sort of thing... after losing three of them we switched that last clematis to being from the same types as the rest so they'd all be flowering about the same times.