Ptelea is a taxonomically complex genus, native in North America and Mexico. Depending on species delimitation Ptelea counts three to 60 species. Some are cultivated as ornamentals but only P. trifoliata is more or less regularly planted.
Bailey H.E., Mooken J.D. & Bailey V.L. (1972) Studies on the geographical distribution of some alkaloids and coumarins in leaf extracts of Ptelea species. Lloydia 34(4): 377-382.
Gorman C. & Nelson E.C. (1997) Ptelea. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 111.
Greene E.L. (1906) The genus Ptelea in western and southwestern United States and Mexico. Contr. U.S. Nat. Herb. 10: 49-78.