As a founding member of Cherokee Garden Club in Atlanta, Helen Hawkins Clarke was involved with community service projects, including the development of the Dolly Blalock Black Memorial Garden at Henrietta Egleston Hospital for Children, as well as flower shows and horticultural courses. She quickly became a prize-winning flower arranger and respected flower-show judge in Georgia and was known for her artistic drawing abilities.

In the 1930s and 1940s, Clarke designed and executed an extensive garden at her home in Peachtree Heights West in Atlanta, combining her love of horticulture with her keen eye for design. An article in the Atlanta Journal on June 26, 1938, described the Clarke garden as a place in which “the beauty of the native forest trees … makes an effective background for the masses of flowers, columbines, foxgloves, hollyhocks, and bee balm. …”

Garden clubs provided some women, such as Clarke, the vehicle to work as a professional in the field of landscape architecture. After raising her daughter, also named Helen, Clarke increased her knowledge by attending landscape architecture classes at the University of Georgia.

She entered college in 1935 at the age of 43, the same year her daughter enrolled as a first-year student. In conjunction with her university studies, Clarke continued gaining horticultural knowledge through her participation in Cherokee Garden Club and Garden Club of Georgia.

Like most other women practicing in this field in the first half of the 20th century, Clarke worked in residential garden design. Clarke worked at the landscape architectural firm of Newberry & Johnson in the 1930s. She later partnered with her friend Perry Hunt Wheeler in 1938 and together they designed residential gardens in Atlanta.

In a 1944 letter, Wheeler asked Clarke if she would consider establishing another partnership with him following World War II, combining a landscape architecture practice with a nursery business , though the plans never came to fruition. Clarke contracted polio in the late 1940s and consequently only practiced as a landscape architect for a decade. She continued to assist close friends and family members with garden designs in the 1950s and 1960s.