Ulmus Pumila - Invasiveness and Spontaneous Hybridization

Invasiveness and Spontaneous Hybridization

In North America, Ulmus pumila has become an invasive species in much of the region from central Mexico northward across the eastern and central United States to Ontario, Canada. It also hybridizes in the wild with the native U. rubra (slippery elm) in the central United States. In South America, the tree has spread across much of the Argentinian pampas In Europe it has spread widely in Spain, and hybridizes extensively there with the native U. minor, contributing to conservation concerns for the latter species.

Ulmus pumila is often found in abundance along railroads and in abandoned lots and on disturbed ground. The gravel along railroad beds provides ideal conditions for its growth: well-drained, nutrient poor soil, and high light conditions, and these beds provide corridors which facilitate its spread. Owing to its high sunlight requirements, it seldom invades mature forests, and is primarily a problem in cities and open areas, as well as along transportation corridors.

The species is now listed in Japan as an alien species recognized to be established in Japan or found in the Japanese wild.