"Horsetail tea is extracted from the common horsetail (Equisetum arvense), a plant especially rich in silica.? Horsetail is best seen as a prophylactic (disease-preventing, not disease-curing) spray with a mild fungus-repressing effect.? During the months when green plants are not readily available, you can prepare an extract by covering dry plants with water and allowing them to ferment in a sunny place for about ten days.? Dried equisetem, available through the Josephine Porter Institute for Applied Biodynamics (2) in Woolwine, Virginia, can also be used to make horsetail tea.?? ?"