Oh, we're all disappointed that clematises look nothing like the pictures on some packages, I'm sure.
A deck railing is good, but you'll have to help the clematis climb it. Its tendrils will wind around small things, like the canes of other plants or the wire on a chicken-wire structure, but they aren't long enough to wind around the larger elements of a deck railing. I twine my vines in and out of the lattice on my deck railing and I sometimes use pieces of velcro tape to hold them in place.
