(Clematis) Clematis tangutica is a vigorous and free-flowering vine. In midsummer, an explosion of 1-2 inch bright yellow lantern-like flowers cover the bright green foliage. The lovely flowers continue to bloom through October and are then followed by attractive seed heads in late fall. Clematis tangutica grows up to 10-20 foot tall and looks stunning when planted over an arbor! Part of prune group 3, tangutica can be trimmed back to the ground each Fall.