Established in 1967 with a gift by Mrs. Clark Diffenback, the long raised mound of Clark Garden was built using recycled excavated soil from a renovated UD building, with a low retaining stone wall running most of its length. Plant donations, such as the large paper bark maple (Acer griseum) from Millcreek Nursery (the former nursery of Mr. and Mrs. William H. Frederick, Jr.), laid the foundation for an extensive woody plant collection. Some of the plants in this garden are the most mature specimens in the UDBG. Other notable specimens include California incense cedar (Calocedrus decurrens), Leonard Messel Loebner's Magnolia (Magnolia x loebneri 'Leonard Messel'), and golden larch (Pseudolarix amabilis). This garden features a diverse collection of ornamental conifers, interspersed with deciduous flowering shrubs and trees and broadleaved evergreen plants which provide ornamental interest throughout the year.