K. caulescens has been growing in my USDA zone 6b (-20.6 C) garden in Central Pennsylvania for at least 10 years in heavy clay. It was moved about 3 years ago to keep it in full sun (shade was overtaking) and on a berm to provide better drainage. I'm hoping it survives this winter's heavy snows and much colder than normal temperatures. Beverly On Monday, March 3, 2014 2:55 PM, Peter Taggart <petersirises@gmail.com> wrote: K northiae survived minus 15C or colder for me and flowered, In my experience K hirsuta sulks if it does not get a hot dry spot. It was also hardy in the recent cold winters. K caulescens died. K uvaria hardy for me too. I have a plant labelled K thomsoni which was also unscathed. Various hybrids, sown as species, such as citrina and baurii were hardy, pauciflora is definately not hardy in cold winters. K typhoides was hardy for many years but I am not sure if I still have it. All in Derbyshire, England Peter