The Sugarberry has mousy gray bark with warts! Little protrusions that look very similar to a Hackberry tree. The difference between the Sugarberry and Hackberry are in their leaf structure. Both have smooth edges along the base base but the Hackberry has small teeth up to the point of the leaf while the Sugarberry has no teeth or teeth that start around mid-way up the leaf. This tree is native to East Tennessee and likes limestone based soil such as we have here on the River Walk.
The Sugarberry on the the Townsend River Walk and Arboretum is quite old and the bark has large protrusions.
Courtesy of Robert H. Mohlenbrock, hosted by the USDA-NRCS PLANTS Database / USDA SCS. 1989. Midwest wetland flora: Field office illustrated guide to plant species. Midwest National Technical Center, Lincoln.