Kolkwitzia is a genus of a single species, Kolkwitzia amabilis Graebner. It is originally native in central and eastern China but has become more or less widespread in cultivation in cold-temperate regions of the world.
Kolkwitzia is here included in Caprifoliaceae, in accordance with recent molecular phylogenetic studies (APGIII 2009). An alternative taxonomy, as a member of Linnaeaceae, was proposed by Backlund & Pyke (1998). This point of view was recently followed in Flora of China by Yang & al. (2011).
APG III (2009) An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants. APG III. Bot. J. Linn. Soc. 161(2): 105-121.
Backlund A. & Pyck N. (1998) Diervillaceae and Linnaeaceae, two new families of caprifolioids. Taxon 47: 657-661.
Landrein S., Prenner G., Chase M.W. & Clarkson J.J. (2012) Abelia and relatives: phylogenetics of Linnaeeae (Dipsacales–Caprifoliaceae s.l.) and a new interpretation of their inflorescence morphology. Botanical Journal of the Linnean Society 169(4): 692-713.
Yang Q., Landrein S., Osborne J. & Borosova R. (2011) Caprifoliaceae. In: Flora of China Editorial Committee (ed.), Flora of China, vol. 19. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 616-641.