White Japanese Anemone.
This is a large white Anemone with golden anthers. It begins to bloom in August, and goes on right through the autumn, long after our summer flowers have gone. Any bit of root you can buy or get given will grow, but when once you have planted it you should leave it alone year after year. It hates being disturbed, and will only make the huge flowering clump you want when it is well established. It likes a rich soil, and grows very well in half-shady places.