It may be worth drawing a distinction between the source of plant knowledge and the source of plant healing. Many indigenous peoples assert that their knowledge of plants and their uses comes from some other-than-human person who appears in a vision or dream. These spirits may, as in the Amazonian mestizo tradition, be the plants themselves, but not necessarily; when my teacher doña María Tuesta was young, for example, it was the Virgin Mary, not the plant spirits, who appeared in her dreams, showed her the healing plants, and taught her the plants to cure specific diseases.

On the other hand, the source of plant healing may be the physical plant, or the physical plant as a substrate of magical power, or the spirit of the plant acting independently of the physical plant. Joel Swerdlow, a scientific journalist investigating plant medicine, tells a story that illustrates this point. In Madagascar, he met with a rural healer who supplied him with leaves of a plant said to be good for cancer. And, indeed, tests by a Swiss pharmaceutical company showed the leaves to have anticancer activity. He returned, but the healer, concerned, probably wisely, about potential theft of his secrets, refused to supply any more leaves. Swerdlow then himself acquired leaves from the same species of plant; yet these, when tested, were ineffective.

To Amazonian mestizo shamans, there is nothing puzzling about this. Swerdlow did not sing to the plants. Herbalists — and this includes poisoners — do not sing; shamanic herbalists and sorcerers sing — charge the plants, cure them, call the spirits that invest themselves in the healing process. “What good do you think my remedies would be,” says don Manuel Córdova, a mestizo shaman, “if I didn’t sing to them?” And the song may be — but is not necessarily — the icaro of the plants who are in the medicine. In curing a woman made pregnant by a boa, Pablo Amaringo tells us, the shaman prepared the fruit of the huito, but then he sang — “singing many icaros, blowing on it, and putting in it arkanas” — calling the great serpent corimachaco, the multicolored rainbow, the precious stones, the mud of the waters, the laughing falcon, the tiger, the spirits of the pucunucho pepper and the hairy rocoto pepper — both hot pepper plants with which to stun the boa who, with its own spirit helpers, was supporting the pregnancy.

As poet César Calvo puts it, the physical plants are simply “the visible portion of the healing.” The plants, in addition to being real medicines, contain madres or genios, the beings who teach. Calvo says that the mothers of things “are the origin of their purpose and of their use for healing or for harming.” When we give the plants our love, we awaken their mothers, ”so that they will augment the strength of the cure with their love.” A cure is not caused by the ingestion or topical application of an herbal medicine; rather it results from the benevolent intervention of the mother through the intermediation of the plant.

Mestizo shamans have an encyclopedic knowledge of the preparation and use of healing plants, and frequently prepare and prescribe plants and plant mixtures for ingestion, baths, and sweats. But a plant is inefficacious by itself; it is the spirit of the plant who heals, and the spirit is summoned by its song. Perhaps the best way to conceptualize this is that, for mestizo shamans, the physical plant is the same as the plant spirit. The physical plant is the aspect of the plant spirit that you can see clearly all the time; the plant spirit is the aspect of the plant you do not notice — you cannot see — until you have drunk ayahuasca.

Thus, shamanic herbalists uniquely develop a personal relationship with the entire plant; the song, the whisper, the whistle, the rattling of the leaf bundle is the manifestation of that relationship in sound, puro sonido, the language of the plants. Biomedical practitioners — or contemporary herbalists who see plants as useful collocations of molecules — lack such a relationship; and they rely for healing on the mercy of a part of the plant with whom they have no relationship at all.