Mystery flower

For 19 years I have traveled down the same 1/2 mile stretch of gravel road on a daily baisis, usually by truck but many times by bike or walking also.

This year for the first time I spoted this flowering bush growing in the ditch beside the road and only in the one place. Whatever it is is well established and appears to have been there for many years, but only in this one place.

It appears to spread by root so I'll have to dig a bit out and see if I can get it growing in the yard.

Interesting...