View photos of the medicinal plant Medicago sativa (Alfalfa), profiled in Herbal Medicine: Trends and Traditions and Medicinal Plants of the Western Mountain States.

From Medicinal Plants of the Western Mountain States:

Just as Alfalfa is a superb tea for nutritional deficiencies due to its tendency of absorbing trace minerals from the soil, it can also be problematic if collected in contaminated areas. The plant picks up a fair share of copper, lead, cadmium, and nickel, therefore it is best to know the soil’s history prior to collection.