A plantation economy is an economy based on agricultural mass production, usually of a few commodity crops, grown on large farms worked by laborers or slaves. The properties are called plantations. Plantation economies rely on the export of cash crops as a source of income. Prominent crops included cotton, rubber, sugar cane, tobacco, figs, rice, kapok, sisal, and species in the genus Indigofera, used to produce indigo dye. The longer a crop's harvest period, the more efficient plantations become. Economies of scale are also achieved when the distance to market is long. Plantation crops usually need processing immediately after harvesting. Sugarcane, tea, sisal, and palm oil are most suited to plantations, while coconuts, rubber, and cotton are suitable to a lesser extent. Plantation economies are factory-like, industrialised and centralised forms of agriculture, owned by large corporations or affluent owners. Under normal circumstances, plantation economies are not as efficient as small farm holdings, since there is immense difficulty in proper supervision of labour over a large land area. When there are large distances between the plantations and their markets, processing can reduce the bulk of the crop and lower shipping costs. Large plantations produce large quantities of a good are able to achieve economies of scale for expensive processing machinery, as the per unit cost of processing is greatly diminished. This economy of scale can be achieved best with tropical crops that are harvested continuously through the year, fully utilising the processing machinery. Examples of crops that are suitable to be processed are sugar, sisal, palm oil, and tea. Plantations in the American South In the Thirteen Colonies, plantations were concentrated in the South. These colonies included Maryland, Virginia, North Carolina, South Carolina, and Georgia. They had good soil and long growing seasons, ideal for crops such as rice and tobacco. The existence of many waterways in the region made transportation easier.