Thuja occidentalis is an evergreen coniferous tree, in the cypress family Cupressaceae, which is native to the eastern Canada and much of the northeastern, northcentral, and east central United States, but widely cultivated as an ornamental plant. Thuja occidentalis grows naturally in wet forests, being particularly abundant in coniferous swamps where other larger and faster-growing trees cannot compete successfully. It also occurs on other sites with reduced tree competition, such as cliffs.