Dr. Michael A. Dirr is a renowned American horticulturist and professor emeritus at the University of Georgia, celebrated worldwide for his expertise in woody plants. With academic roots in Plant Physiology—holding a B.S. and M.S. from Ohio State University and a Ph.D. from the University of Massachusetts Amherst (1972)—he has left an indelible mark on horticulture through teaching, writing, research, and plant breeding.

     Over his influential career, Dirr helmed the Georgia Plant Introduction Program and has introduced over 200 new plants to the nursery trade. He has authored 10 books, including the iconic Manual of Woody Landscape Plants and Dirr’s Encyclopedia of Trees & Shrubs, along with more than 300 publications. He is also the inventor or co-inventor on 86 plant patents, underscoring his profound impact on modern horticulture.

     Dirr’s innovative breeding led to the development of the Endless Summer® series of hydrangeas, which transformed the hydrangea world forever. Additionally, he and his partners—Jeff Beasley and Mark Griffith at Premier Introductions, Inc.—have bred, selected, and introduced cultivars across a remarkable range of genera, including Abelia, Acer, Baptisia, Bignonia, Buddleia, Calycanthus, Clethra, Cornus, Distylium, Fothergilla, Fraxinus, Ginkgo, Hydrangea, Hypericum, Ilex, Itea, Lagerstroemia, Loropetalum, Magnolia, Nandina, Prunus, Punica, Quercus, Ulmus, Viburnum, and Vitex.

       Currently, Mike and his partners are actively advancing genetics in Camellia, Chamaecyparis, Cupressus, Cyrilla, Juniperus, and Phillyrea, as well as the herbaceous perennials Amsonia and Spigelia. Their philosophy is to treat every genus as a potential “genetic gold mine” as the journey to develop exceptional garden plants continues.