Koelreuteria paniculata Laxm. (China) – A very rare but increasing escape from cultivation. Probably first recorded in the wild in the city of Leuven in 2008. Since then regularly recorded, often in urban areas and in the immediate surroundings of planted individuals (e.g. in Antwerp, Brussels, Genk, etc.). In such instances Koelreuteria paniculata appears to be very prolific and often seeds abundantly (saplings found in cracks of concrete, at foot of walls, etc.). Off-set, however, is usually readily removed. In 2014 Koelreuteria paniculata was observed for the first time in a riparian habitat, i.e. between basalt blocks of river Rupel in Boom (a single individual). By 2017 it was noticed to have reached maturity in this locality and further dispersal is likely. Also in 2017 a second individual was recorded in an identical habitat along river Scheldt in Kruibeke. Koelreuteria paniculata likely will naturalize in riparian habitats in a near future, as it did before in the Netherlands (van der Meijden & al. 1996). It is also naturalized elsewhere in western Europe, for instance in France (Tison & de Foucault 2014) and the British Isles (Stace 2010).
Selected references
Dirr M.A. (1976) The goldenrain tree. Amer. Nurseryman 144(10).
Lockley R.E. & Lockley M.H. (1976) Koelreuteria paniculata. Garden (London) 101(7): 392.
Meyer F.G. (1976) A revision of the genus Koelreuteria (Sapindaceae). J. Arnold Arbor. 57(2): 129-166. [available online at: https://www.biodiversitylibrary.org/item/41448#page/137/mode/1up]
Mullin J.M. (1988) Kolreuteria paniculata Laxmann in London. B.S.B.I. News 49: 30-31. [available online at: https://archive.bsbi.org.uk/BSBINews49.pdf]
Pohl K. (1976) Der Blasenbaum und seine schone Schwester. Palmengarten 40(3): 101-102.
Sasaki Y. & Ohashi H. (2007) Natural distribution and habitat of Koelreuteria paniculata Laxm. (Sapindaceae) in Japan and its new form (in Japanese). J. Jap. Bot. 82(3): 160-174. [available online at: http://www.jjbotany.com/pdf/JJB_082_160_174.pdf]
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Tison J.-M. & de Foucault B. (coord.) 2014) Flora Gallica. Flore de France. Editions Biotope, Mèze : xx + 1196 p.
Van der Meijden R., Holverda W. & Duistermaat L. (1996) Nieuwe vondsten van zeldzame planten in 1993, 1994 en (ten dele) 1995. Gorteria 22: 57-81. [available online at: http://natuurtijdschriften.nl/download?type=document;docid=536971]
Wade A.E. (1951) Koelreuteria paniculata Laxmann. Watsonia 2: 106. [available online at: http://archive.bsbi.org.uk/Wats2p104.pdf]