When Europeans came across the New World, they were presented with an entire new system of healing: new plants and new people who had devised new methods to use them. Some of the plants were familiar. Willow, for instance, grows in the Old World and the New and is the basis of the modern aspirin. Others, completely unknown, would soon appear in the settlers' medicine chests, so to speak, alongside their old favorites from home.
While many Native American families would have common plants for common ailments at hand, medicine was often spiritual for more complex ailments, appeasing the bad spirits that were making a person sick, as well as providing the physical remedy. Among the Chippewa of Minnesota, for instance, the medicine men would not just pass on the remedies to anyone, worried that they would not treat the plants with proper respect. Plants were often not even given names to keep them properly revered. Just as a hunter would present an offering of tobacco for the animal they killed to feed them, so too would the medicine men offer tobacco to the plant being used to heal them. Bloodletting, the scourge of Old World medicine, had its place as well, though perhaps it would be said that it was used with more medical purpose than letting out evil humors--when a fall had created too much blood in an area or a sprain had caused the area to swell substantially, for instance. Amputation was also practiced, with nothing more than dried wild cherry bark applied to the wound, often without incident of infection.
If a man was spitting up blood, they made a tea of the spike moss flowers. A tea made of fireweed roots and its inner stem would relieve constipation. These were just a few of the remedies the Blackfoot employed, but every people had their own indigenous plants. It's interesting to note, though, that while the plants stayed in the same in a general region, each tribe would give it its own use as well.
Sage, for instance, a widely available plant across much of the western part of the US, was commonly used for ceremonial purposes. They purified the body before ceremonies or used it as incense, not to mention as protection against evil influences. But among the medicinal uses, you come across much more variety. The Dakota used it for stomach ailments. The Lakota made a tea to remedy constipation, inability to urinate, difficult childbirth, and menstrual irregularity. The Cheyenne would use crushed leaves as snuff for sinus attacks, nosebleed and headache. The Crow used a salve of sage on sores, as a tea for eczema and a deodorant. The Kiowa made a tea to reduce phlegm and lung complaints, as well as stomach complaints. The Mesquakies used it as a poultice for sores and to treat tonsillitis and sore throat. The Omaha used to to bathe in and as a powder to inhale for nosebleeds. I could go on with as many uses as there are tribes. Sage is, of course, common on many a spice rack now, but modern medicine has found that its use as a wash for the skin, helping to break a fever, coughing, and sore throats. Many of the varied reasons that it was used for have turned out to be true.
What the Pipsissiwa once used for kidney stones, bladder inflammations and as an astringent for eye washes is now a secret ingredient in certain soft drinks, causing it to disappear in some areas. Take a look sometime at the vitamin and supplement section and you'll find all sorts of plants that were once carried in a medicine mans pouch.
How Indians use Wild Plants for Food, Medicine, and Crafts by Frances Densmore
Medicinal Wild Plants of the Prairie by Kelly Kindscher
Uses of Plants by the Indians of the Missouri River Region by Melvin Gilmore
Edible and Medicinal Plants of the West by Gregory Tilford
Indian Herbology of Noth America by Alma Hutchens