There are a huge number of plants that are used by the Native Americans for the purposes of healing. Many of those are quite important to "traditional" medicines. For instance, Aspirin was "invented" to mimic the substances found naturally in the cambium (inner bark) of Willows.

A person doesn't need to become a shaman, nor go to a shaman, in order to use medicinal plants. There are a large number of books, many of them quite good, that cover how to use the plants, when to collect them, what they look like, and so forth. There are also a number of excellent websites that have this information, including my own site, and botanical.com.

One thing to be aware of is that though it is rare, a person can be allergic to any substance, and this includes herbal plants. So the first time you try a preparation, it is a good idea to try only a small amount of it, and wait a day to see if there is a reaction. I recommend doing this BEFORE you would be actually using the plant for medicinal purposes. For instance, Horehound tea is an excellent preparation for colds. So try drinking a small amount before cold season, to make sure that you can drink it without problems. (You can purchase horehound tea in many stores and don't even need to go out in the woods to get it. A warning...horehound tea is bitter, so sweeten it with honey.)

Another thing that can't be overstated...if you have any question about the identity of a particular plant, do not use it. There are also books that are good for identification, but the best way is to go out into the woods with someone who knows what the plants look like, and have them point out the various plants that are used. If anyone has a question about a particular plant, as far as usage, collection, or what have you, you are welcome to ask, too. Many plants are now available at least in health food stores, since alternative medicine is becoming more popular.

Now that I've given the down side of wild plants, the up side is that these are natural substances, and your body is much less likely to have adverse reactions to them, unlike man made medicines. Willow cambium seldom upsets the stomach like aspirin does, for example. For upset stomach, peppermint tea is far better for you than the chemical compositions available in the store. And horehound tea, or garlic lemon tea, is far better for you than the cold medicines on the shelf of the pharmacy. Be good to your body. It is the only one you have!