Serrated kidney-shaped leaves that stay green through the winter and a profusion of small blue flowers in spring. An attractive but aggressive ground-cover for shady or moist places - it can be invasive. Used as an astringent, diuretic, stimulant, and tonic, it is considered beneficial to the kidneys and mucous membranes. Leaves, which are high in vitamin C, can be eaten in salads or steamed. Formerly used to flavor and clarify ale and as a rennet in cheese-making.