Magnoliaceae
Magnoliaceae encompasses two genera that are widely offered for sale by the horticultural trade, Liriodendron and Magnolia. Representatives of both are frequent in Belgian gardens as well and at least a species of the former has been reliably recorded as an escape (L. tulipifera). An unidentified species of Magnolia was observed in 2017 in Beez, on the quay of river Meuse.
Literature
Gabara B. (2001) Phylogenetic relationships in family Magnoliaceae inferred from ndhF sequences. Amer. J. Bot. 88: 717-728.
Meyer F.G. (1997) Magnoliaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 3. Oxford University Press, New York-Oxford: 3-10. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=10530]
Spicer R.A. (1983) Magnolias and tulip trees. Living Countryside 11(123): 2441-2443.
Spongberg S.A. (1976) Magnoliaceae hardy in temperate North America. J. Arnold Arbor. 57(3): 250-312. [available online at: https://www.biodiversitylibrary.org/part/28167#/summary]
Xia N., Liu Y. & Nooteboom H.P. (2008) Magnoliaceae. In: Wu Z.Y. & Raven P.H. (Eds.), Flora of China, Vol 7. Science Press, Bejing, pp. 48-91. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=10530]