I would recommend Clematis Tangutica. It flowers quite late in the summer and is different from the usual clematis in as much as they are yellow 'lantern' shaped ones. You also get the added bonus of what can only be described as fluffy seed heads throughout the autumn. If you want to know what's flowering now visit your local garden centre and see what's in bloom. One thing to remember "If it flower's before June, don't prune" So if you want it to cover an old shed or unsightly wall you need to purchase one that's just finishing flowering otherwise all summer bloomers need to be cut hard back. Also, keep their heads in the sun and roots in the shade and water well. Good luck in finding what you want. Mrs. N.