From rich mesic woodlands of Eastern N America, often, but not always, on limestone, the 'Richweed' or 'Stoneroot' is a member of the mint family. The roots were long used medicinally by Native Americans for a number of common complaints, such as good ol' haemorrhoids. As a garden plant it's useful for shaded areas, with large oval foliage from dark, square stems, topped by pyramidal clusters of soft-yellow flowers in September. Both flowers and foliage emit a citronella fragrance and the leaves are used for tea. Height 1m.