Caryopteris xclandonensis Rehd. (= C. incana (Houtt.) Miq. x C. mongholica Bunge) (Hort.) – A very rare but increasing escape from cultivation. Sometimes very persistent but not (yet) genuinely naturalized. Apparently first documented from Mol and Kortrijk in 2011. In the latter locality two young, self-sown bushes grow on a brick quay wall of river Leie. In 2013 also observed in Meerhout.
Caryopteris xclandonensis is widely grown as an ornamental shrub in Belgium and elsewhere in western Europe. Yet, it seems to be rare as an escape from cultivation. It is known as such, for instance, from Germany (Adolphi 1995) and the British Isles (Clement & Foster 1994).
Adolphi K. (1995) Neophytische Kultur- und Anbaupflanzen als Kulturflüchtlinge des Rheinlandes. Nardus 2: 272 p.
Beharrell N. & Culham A. (2006) The origin of Caryopteris x clandonensis and its cultivars. Plantsman 5(3): 192-197.
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Pattison G. (1989) Caryopteris xclandonensis. Plantsman 11(1): 15-18.