Born in Louisiana, Dormon received a B.A. in art from Judson College in 1907. She taught in public schools before returning to her parent’s summer retreat, Briarwood, in Natchitoches Parish. A self-taught landscape designer and horticulturalist, she began cultivating irises in the 1920s and later helped popularize their use. At the same time she became the first woman to work for the Department of Conservation - Division of Forestry, and created Louisiana’s first conservation education program. As the Chairman of Forestry for the Louisiana Federation of Women’s Clubs and the first female member of the Society of American Foresters, she was instrumental in the campaign to save and designate the Kisatchie National Forest in 1930, a 600,000-acre forest of longleaf pines. After leaving the Division of Forestry she worked as landscape consultant to Louisiana’s Board of Public Welfare and the state’s Highway Department.
Dormon’s naturalistic designs emphasized the wild landscape. She corresponded frequently with Elizabeth Lawrence and worked with Ellen Shipman on the gardens at Longue Vue in New Orleans. Other projects include Hodges Gardens, Louisiana and her own gardens at Briarwood.
Throughout her career, Dormon lectured and published on conservation issues, plants and gardening. Her publications, many of which she illustrated, include Forest Trees of Louisiana and Wild Flowers of Louisiana, and she was a frequent contributor to Home Gardening for the South. She helped establish the Louisiana Iris Society and was awarded the Eloise Paine Luquer Medal by the Garden Club of America.