An ethnobotanist was a scientist who studied in the field of ethnobotany, that is, the science related to botany, specifically involved in the study of the relationship between plants and humanoid life.
One of Doctor Beverly Crusher's hobbies was ethnobotany. (TNG: "Clues")
This hobby may have some connection to Felisa Howard's use of natural remedies in her work as a healer, which inspired Crusher to her career in medicine, which was referenced in TNG: "The Arsenal of Freedom".
In 2257, Lieutenant Commander Paul Stamets stated that a former colleague of his was an ethnobotanist aboard the USS Enterprise. (DIS: "Brother")