Acer pensylvanicum L. (incl. hybrids) (N Am.) – An exceptional escape from cultivation. A single self-sown tree grows in young woodland in Berendrecht (Opstalvallei) since at least 2010.
Acer pensylvanicum is much reminiscent of A. rufinerve, a locally invasive species in woodlands in Belgium (see there). Both are members of the Macrantha section, a group of species characterized by a remarkably striped bark. Compared with the latter, A. pensylvanicum tends to have slightly larger leaves (up to 18 cm wide) and twigs that are not pruinose (vs. young shoot clearly covered with +/-whitish-blue bloom in A. rufinerve).
This species is regularly planted as an ornamental tree in Europe. However, records in the wild seem to be rather exceptional. Wilmore (2000) reported about escaped individuals in Yorkshire in the British Isles.
Acer xconspicuum van Gelderen & Oterdoom (van Gelderen & al. 1994), a hybrid of A. pensylvanicum and the Chinese A. davidii Franch., is very similar and also frequently planted (Roloff & Bärtels 2006). It tends to have less hairy lower leaf surfaces.
Selected references
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Van Gelderen D.M., de Jong P.C. & Oterdoom H.J. (1994) Maples of the World, 458 p.
Wilmore G.T.D. (2000) Alien plants of Yorkshire. Yorkshire Naturalists' Union.