UNITED STATES NATIONAL ARBORETUM

arboretum in Washington, D.C., operated by the U.S. Department of Agriculture, occupying 415 acres (168 hectares) on the west bank of the Anacostia River. Among the more than 7,000 kinds of plants are special collections of camellias, hollies, apple trees, and slow-growing conifers. The arboretum was established in 1937.