Horsetail - Equisetum arvense
The primary use of the Horsetail is as a diuretic, but in very high doses horsetail is a sedative and an anticonvulsant. Gently stimulating increased urinary flow, horsetail helps "flush" infectious bacteria out of the bladder without altering the body’s balance of electrolytes. The powdered form of the herb is better when electrolytes may be depleted.
Horsetail is also the form of the herb being investigated as a treatment for age-related memory impairment.