This widely planted tree ("Siberian elm") was first recorded as an escape in Ky. by Ellis et al. (1971; APSC). The colls. mapped here appear to be from self-seeded plants, based on label data. Most data come from CW, who indicated that this species is becoming naturalized across the state, especially in urban areas. However, well-documented invasion appears to be rare in most of Ky. and in more southeastern states. Further west, especially in the Great Plains, this species is much more commonly naturalized (K). It can hybridize extensively with rubra, and it is generally somewhat resistant to Dutch Elm Disease (Zalapa et al. 2010; Elowsky et al. 2013). However, it is not generally recommended for ornamental uses, due to brittle branches, pests and pathogens (missouribotanicalgarden.org).