In Hawaii, the study of healing with plants is called La'au lapa'au. The following is an excerpt from an essay in my documentary book Women Healers of the World:

La’au lapa’au

The medical practice of healing in ancient Hawai’i centered around the use of plants, a practice which became la’au lapa’au, or herbalism. Typically a child (usually male, but not always) was identified by his elders when he was young as possessing healing potential and gifts that would make him a successful healer. He would be trained throughout adolescence and would be given tests once he reached adulthood. If he completed these tests there would be great ceremonies that solidified his status as a healer, and he would choose his specialty. He would become a kahuna, or priest.

The discipline was advanced and the areas of healing ability were very specific, though it must be understood that all healers were inherently spiritual priests, as well. The two disciplines of medicine and religion went hand-in-hand for the betterment of the patient and for the health of the community as a whole.

In the ancient Hawaiian medical system—before Cook invaded the islands—new healers were taught the following skills, in this order:

Learning all matters pertaining to the gods, “from whom all knowledge came.” 

Learning prayers of thanksgiving and prayers to the gods;

Learning the kinds of disease;

Learning remedies for disease;

Learning the art of killing;

Learning the art of saving life. (Gutmanis, 15)

According to noted Hawaiian cultural scholar George Kanahele, once indoctrinated as a priest and healer, the new kahuna could choose from the following specialties:

Kahuna la’au lapa’au: a priest and trained expert in traditional Hawaiian herbal medicine;

Kahuna haha: priest or doctor who performed diagnosis by feeling with the fingers;

Kahuna ‘ea: specialized in treating inherent disorders

Kahuna ‘o’o: treated infants to close the anterior fontanel

Kahuna paaoao: pediatricians for infants

Kahuna ho’ohapai keiki and kahuna ho’ohanau keiki: gynecologists and obstetricians

Kahuna ha’iha’i-iwi: bone setter

Kahuna lomilomi: physical therapist/massage therapist/osteopath

Kahuna ‘ana ‘ana: priest trained in death prayers

To read more about this and16 other incredible world healing and health traditions, see the book Women Healers of the World