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