I have been trying to cross purple top x Shogun . I think I had success . Shogun will overwinter in zone 5 but purple top does not . Shogun is too strong for my taste . I like to use the flower buds like broccoli rab in the spring as well as eating the root in the fall . These have purple tops . Been growing both for years but was hoping to cut back to one .This is the usual result on overwintering purple top .