A plantation is a large artificially established forest, farm or estate, where crops are grown for sale, often in distant markets rather than for local on-site consumption. The term plantation is informal and not precisely defined. Crops grown on plantations include fast-growing trees (often conifers), cotton, coffee, tobacco, sugar cane, sisal, some oil seeds (notably oil palms) and rubber trees. Farms that produce alfalfa, Lespedeza, clover, and other forage crops are usually not called plantations. The term "plantation" has usually not included large orchards (except for banana plantations), but does include the planting of trees for lumber. A plantation is always a monoculture over a large area and does not include extensive naturally occurring stands of plants that have economic value. Because of its large size, a plantation takes advantage of economies of scale. Protectionist policies and natural comparative advantage have contributed to determining where plantations have been located.