Nichols Arboretum, locally known as the Arb,: 22  is an arboretum on the campus of the University of Michigan, in Ann Arbor, Michigan. The Arb is located adjacent to the Huron River, and features over 400 species, including 110 species of trees, in a varied, hilly landscape. A signature feature of Nichols Arboretum is the W. E. Upjohn Peony Garden, which features the largest collection of heirloom peonies in North America.