The Thornless Grafted Mesquite, trademarked by Mountain States Wholesale Nursery, is the South American Mesquite grafted onto the rootstock of our native Velvet Mesquite. Hardy in both the Tucson and Green Valley areas, this is an option if you just absolutely need to have a thornless mesquite.
The theory is that this tree has the fast growing characteristics of the South American Mesquite, but the deep root system of the Velvet Mesquite, reducing the likelihood of the tree blowing over during storms; as the South American species is prone to do.
While having a thornless mesquite is certainly a nice option, there is still the concern that hybrids are crossing with our native mesquites, with the potential of eliminating natives altogether. Losing a species is never a good idea, as there are always consequences to other species unknown at this time.
Reference: Mountain States Wholesale Nursery and Gregg Starr Nursery Plant Info Sheet, 1999.