Persicaria polymorpha

The Persicaria polymorpha is the large white flower in the middle of the picture. In my opinion it is one of the most sensational perennials. It grows 150-200 cm high and the same large. It blooms from early summer to late autumn. It lives both in sunshine and in part-shade, and on every soil. Although originally a marsh plant, it quite well tolerates dryness, but it does not like too wet soil. Nevertheless, it is fond of regular irrigation. It is extremely frost hardy (Z3). Its only flaw is that nobody produces it here at us. (But perhaps now, after this post, someone will.)

You can read a detailed description of it on the site of Bluestem Nursery. And since you are there, it is well worth to look around.