The most well-known medicinal plant in our area is called "ratroot", also called wild ginger or sweetflag. I believe the scientific name for this plant is Acorus calamus. I know it is a plant that grows in marshy areas (and munched by the muskrat) and the root is harvested and used to make teas or to be chewed directly. At the very least, there don't seem to be any significant toxicities related to it. Its actions are usually described as a general "cure for what ails you". Like any good medicinal agent, it tastes terrible! Some locals harvest it, and it can be purchased from the trading post. Here is a picture of some ratroot we keep around the house, for no particular reason:
Some medicinally or ethnically important plants in my yard:
Willow: tree that contains salicin, a natural "aspirin"; branches of willow can be used to construct sweatlodges, and thus the steam produced inside could contain salicin.
Digitalis (Foxglove): contains a cardiac glycoside, which slows the heart rate, which also explains how it can kill you.
Convallaria majalis (Lily of the Valley): contains cardiac glycosides
Mondarda didyma (Bergamot, Oswego Tea): the Oswego natives (eastern Canada/US) made tea from this citrusy-scented herb.
Yarrow and Saskatoonberry grow wild, and both were important to indigenous peoples.
Also, Thymus vulgaris (Thyme)Lavandula angustifolia (Lavender)Echinacea purpurea (Purple coneflower).
Other traditional medicines still used in the local northern communities are bear grease and spruce gum (usually rubbed into the skin for rashes, but more often the spruce gum will increase irritation in eczema or psoriasis). Though probably a more recent remedy, the use of lard for a variety of ailments is common. Some women believe that eating a large amount of it will bring on labour. If not childbirth, the vast amount of fat should at least bring on the pain of a gallbladder attack.
Unfortunately, there is little remaining knowledge of traditional medicines. This is probably due to the colonial institutions that suppressed traditional practices and tried to force western medicine on the local peoples. Of course, at the time of colonization, there were no great cures for tuberculosis, so native people knew schools and hospitals as places to aquire and die of lung disease. Due to various social issues, tuberculosis is still common among Canadian Aboriginal communities. A few years ago, I read an interesting book on the social and medical history of the local peoples:
Maureen K. Lux, "Medicine That Walks: Disease, Medicine, and Canadian Plains Native People, 1880-1940". University of Toronto Press, 2001.
From the back cover: "Biological invasion, Lux argues, was accompanied by military, cultural, and economic invasions, which combined with both the loss of the bison herds and forced settlement on reserves, led to population decline. The diseases killing the plains Aboriginal people were not contagious epidemics but the grinding diseases of poverty, malnutrition, and overcrowding."