This annual is widely scattered in eastern North America, but uncommon to absent on the southeastern Coastal Plain. It is locally common in thin woods and fields on medium acid soils, especially where deer are abundant and in old roughly grazed pastures. This highly aromatic "American pennyroyal" generally repels consumption by insects and mammals, partly due to the presence of the monoterpene pulegone, which can become toxic in larger doses (Gordon et al. 1982). The "Big Barrens" on the extensive karst plain in western Ky. became known as the "Pennyrhile" region after settlement, presumably due to proliferation of this species after settlement--and perhaps in response to livestock.