Clematis stans is a variable species, and though its flowers differ over a narrow range they are not all alike. In different forms they may vary in shape from slender to chunky, and in colour from white (through skimmed-milk) to a soft lavender-blue. Not to mention that a great part of the attraction of this species lies elsewhere, in its handsome coarse foliage and the intricate branching of its upper reaches.
It is native to Japan, where it is called kusabotan. It is not a vine, but a sub-shrub—the sort of clematis that is usually described as "herbaceous erect," though it can in some situations develop a woody base. Every year it forms a new clump of strong free-standing stems, each bearing three widely-separated toothy-edged leaflets, which have the valuable garden trait of holding their fresh green colour even through the season of bloom. It is a trait they share with the closely-related C. heracleifolia, and the species is still sometimes found in nursery lists as C. heracleifolia var. stans. - from Clematis International.
It vaguely resembles the native, Clematis viorna.