Catalpa ovata G. Don (China) – An exceptional but possibly overlooked escape from cultivation. Known since at least 2008 from the city of Mons: self-sowing in relative abundance near a park (cracks in pavement, foot of walls, plantations, etc.). Most saplings are regularly removed and Catalpa ovata behaves like an undesirable weed. Since 2010 furthermore found on an old brick quay wall of a city canal (Visserij) in Gent (a single, flowering specimen, obviously present since several years). Self-sown plants are also regularly reported from the Antwerp Zoo.
In parts of Germany, for instance the Frankfurt-area, Catalpa ovata is more frequent than C. bignonioides (see: http://flora.com2-gmbh.de/customer/sng_flora/foto/createPDF.php?id=3578 and http://flora-frankfurt.senckenberg.de/root/index.php?page_id=14&id=3578).
Burk C.J. & McMaster N.D. (1988) The spread of Catalpa ovata G.Don in western Massachusetts and its biogeographic implications. Rhodora 90(864): 461-464.
Schmid M. (2005) Untersuchung zur neophytischen Gehölzflora im Stuttgarter Stadtgebiet. Jh. Ges. Naturkde. Württemberg 161: 178-257.