From wikipedia, http://en.wikipedia.org/wiki/Ulmus_rubra the binomial name for the slippery elm is 'ulmus rubra'. Maybe with that information you can ask in the botanical garden (in front of the BA zoo) if they know what it's called in Spanish and where to find it (they usually are helpful).
Thank you all for your suggestions....this was for my cat who was having issues with upset tummy from urping fur balls...he is fine now...I read where cat nip can help calm their stomachs so used a little I had and it did help some...to hot to soon and was loosing his Winter coat to fast..poor guy!