1) Expert on medicinal plants 2) Folk-medicine practitioner 3) Healer 4) Herb doctor 5) Medicinal plant therapist 6) Medicinal-plants adept 7) Practitioner of folk medicine 8) Therapist 
• (n.) One skilled in the knowledge of plants; a collector of, or dealer in, herbs, especially medicinal herbs.
Those who make herbal concoctions, also known as apothecaries.
Herb'al·ist noun One skilled in the knowledge of plants; a collector of, or dealer in, herbs, especially medicinal herbs. 
Herbalist: One versed in herbal lore and, in regard to therapy, an herb doctor.
[n] - a therapist who heals by the use of herbs