Hugh Graham Dargan, ASLA from Darlington County, South Carolina earned a Bachelor of Landscape Architecture from University of Georgia in 1973 and founded Hugh Dargan Associates the same year. He studied historic preservation of landscapes at West Dean College in West Sussex, England. Mary Palmer Kelley Cooper Dargan, ASLA from Nashville, Tennessee earned her bachelor's in botany from University of Tennessee, in 1976 and a master's in landscape architecture from Louisiana State University in 1981. The Dargans practiced landscape architecture for 12 years in Charleston, South Carolina, married in 1985 and moved to Atlanta in 1993. In 2000 the Dargans renamed their firm Dargan Landscape Architects, Inc.

Hugh Dargan is a founding board member of the Southern Garden History Society. Mary Palmer Dargan is a founding member of the advisory committee of the Garden Conservancy of America. The Dargans have each taught at the University of South Carolina and The Art of Landscape Design Studio in Charlotte, North Carolina and other locations. Mary Palmer Dargan has also taught landscape architecture at Clemson University, South Carolina. The Dargans have published several books including Lifelong Landscape Design (2012) and are also frequent lecturers. The Dargans have earned numerous project awards from organizations such as the American Society of Landscape Architects. The Dargan gardens have been featured in many magazines, such as Southern Accents,Garden Design,HG, as well as the Home and Garden Television (HGTV) seriesGround Breakers.