The tree was first named as part of Ulmus americana in 1753, but identified as a separate species, Ulmus rubra, in 1793 by Pennsylvania botanist Gotthilf Muhlenberg. The slightly later name U. fulva, published by French botanist André Michaux in 1803, is still widely used in dietary-supplement and alternative-medicine information.
https://en.wikipedia.org/wiki/Ulmus_rubra
Ulmus fulva og Ulmus rubra er præcis den samme plante –Ulmus fulva er blot synonym for Ulmus rubra
https://unitedplantsavers.org/species-at-risk-list/slippery-elm-ulmus-rubra/
