Clematis tangutica (Maxim.) Korsh. (E USSR, China) – A very rare and probably ephemeral escape from cultivation. First seen in 2000 on the banks of river Schelde near Doel (confirmed there in the subsequent years but probably gone now). In 2007 seen as an occasionnal escape in Roeselare and in 2010 in Lommel.
Clematis tangutica is part of a complex group of yellow-flowering species (e.g. Brandenburg 1989, Roloff & Bärtels 2006). It is probably the most widely cultivated species of the aggregate (Pringle 1997) but others have also been recorded as escapes in Europe. The most notable is C. orientalis L. (e.g. Denmark, Spain; Jonsell 2001, Ferrer Gallego & Guara Requena 2006, Fernández Carvajal 1986) although it is unclear if plants in horticulture under that name correspond with the wild species (Brandenburg 1989). C. orientalis has more numerous flowers per inflorescence (usually 3-15 vs. solitary in C. tangutica), paler flowers (pale or greenish yellow vs. yellow) and leaflet margins usually are entire (vs. denticulate) (Wang & Bartholomew 2001). The whole section was recently reviewed by Wang (2006). He separates both on sepal characters: glabrous inside (C. tangutica var. tangutica) or puberulous (C. orientalis).
Clematis tangutica is a vigorous climber and often considered an invasive species. This is particularly true, for instance, in Canada (Canadian Food Inspection Agency 2008).
Selected literature
Black M. (1981) Clematis tangutica. Hort. Northwest 8(2): 21-24.
Brandenburg W.A. (1989) Clematis. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 3. Cambridge University Press, Cambridge: 357-364.
Brandenburg W.A. (2000) Meclatis in Clematis: Yellow flowering Clematis species. Systematic studies in Clematis I. (Ranunculaceae), inclusive of cultonomic aspects. Wageningen: Wageningen Universiteit. [available online at: http://edepot.wur.nl/199006]
Canadian Food Inspection Agency (2008) Invasive Alien Plants in Canada. CFIA. Ottawa, ON: 72 p. [available online at: http://publications.gc.ca/collections/collection_2008/inspection/A104-74...
Fernández Carvajal M.C. (1986) Clematis. In: Castroviejo S. (ed.), Flora Iberica, vol. 1. Real Jardín Botánico, Madrid: 268-272. [available online at: http://www.floraiberica.es/floraiberica/texto/pdfs/01_036_15_Clematis.pdf]
Ferrer Gallego P.P. & Guara Requena M. (2006) Nuevos datos sobre la asilvestrada Clematis orientalis L. (Ranunculaceae) en la Peninsula Iberica. Flora Montiberica 33: 64-77. [available online at: https://dialnet.unirioja.es/servlet/articulo?codigo=2117504]
Jonsell L. (2001) Clematis. In: Jonsell B. (ed.), Flora Nordica, vol. 2. The Bergius Foundation, Stockholm: 297-299.
Pringle J.S. (1997) Clematis. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 3. Oxford University Press, New York-Oxford: 158-176. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=107312]
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Wang W.-T. (2006) A revision of Clematis sect. Meclatis (Ranunculaceae). Acta Phytotax. Sin. 44(4): 401-436. [available online at: http://www.plantsystematics.com/qikan/manage/wenzhang/f05-0049.pdf]
Wang W.-T. & Bartholomew B. (2001) Clematis. In: Zu Z.-Y. & Raven P., Flora of China, vol. 6. Beijing: Science Press & St. Louis: Missouri Botanical Garden Press. 97-165. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=107312]