Ptelea trifoliata L. (incl. P. isophylla E. Greene, P. serrata Small) (N-Am.) – A very rare escape from cultivation. Known since at least the 1940’s from zinciferous spoil-heaps in Angleur (Lambinon 1959) and apparently locally naturalized (reproducing from seed). Occasionally recorded elsewhere as single young trees, apparently also self-sown. Known for instance from a disused railway yard in Gent since 1996 (Verloove 2002) but now probably destroyed. Most of the other claims probably refer to plantations or relics of former cultivation.
Selected literature:
Bailey V.L., Herlin S.B. & Bailey H.E. (1971) Ptelea trifoliata ssp. trifoliata (Rutaceae) in deciduous forest regions of eastern North America. Brittonia 22(4): 346-358.
Brückner C. (1991) Fruchtanatomische Studien an Dictamnus albus L., Zanthoxylum simulans Hance, Ptelea trifoliata L. und Ruta graveolens L. (Rutaceae). Feddes Repert. 102(7-8): 541-570.
Lambinon J. (1959) Excursion du samedi 6 juin 1959 sur les terrains calaminaires d’Angleur. Nat. Mosana 12(2): 34.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.