Many years ago I was checking out the end-of-season 50% off plant sale at a local store. Amongst the sad looking half dead plants that were left, I found a very healthy looking perennial. Only one problem...no identification tag. Oh well, it was cheap and I thought it would be fun to see what it turned out to be. As of now I still have no idea what it is, lol! For years I've looked for it in plant books to no avail, and I have begun the internet search. But you know how that can be. Even typing in "white flowering perennial" you get "1 through 5" of 1,728,247 sources. So I still have a few sites to check out, ha ha. However, I thought perhaps there might be someone out in net world who knows what this is. Each flower is a single stalk, and it spreads like crazy. I like the plant, but you absolutely need to plant it where you can control it's growth. It sends runners out underground and can easily take over a bed.
I shall continue to investigate.