Pterostyrax Siebold & Zucc.
Pterostyrax is a genus with four species, all native in China, Japan and Burma. Two or three species are cultivated as ornamentals in Europe (Wann 1997, Roloff & Bärtels 2006, Janssen 2018) and, out of these, one has been found as an escape from cultivation in Belgium, P. hispida Siebold & Zucc.
Literature:
Hwang S.M. & Grimes J. (1996) Styracaceae. In: Wu Z.Y. & Raven P.H. (Eds.) Flora of China 15. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 253-271. [available online at: http://flora.huh.harvard.edu/china/mss/volume15/Styracaceae.published.pdf]
Janssen J.J.C. (2018) Pterostyrax - Sortimentsoverzicht. Dendroflora 54: 94-103.
Mulligan B.O. (1981) The Styrax family in the Arboretum. Univ. Wash. Arbor. Bull. 44 (1): 3-10.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Spongberg S.A. (1976) Styracaceae hardy in temperate North America. J. Arnold Arbor. 57(1): 54-73.
Wann J.D. (1997) Styracaceae. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 570-573.