Citrus is the genus of oranges, lemons, limes and grape fruits. The Citrus plants and related plants grow wild in Asia, the East Indies, Australia and tropical Africa. The plants are grown as fruit trees and shrubs, producing juicy fruits for human consumption. Citrus plants belong to the family Rutaceae. The fruits develop on Citrus trees, that often carry evergreen and leathery leaves. The fruits have a juicy pulp and a thick peel and are well known for their sweet or sour taste. Citrus plants commonly have white flowers growing in clusters. Among the best known Citrus fruits are Sweet Orange (C. sinensis), Lemon (C. limonia), Grapefruit (C. paradisi) and Lime (C. aurantifolia) and Tangerine (C. reticulata). The fruits are often best enjoyed fresh, while they add flavour to a variety of food products, ranging from sweets and fruit juices to fish and meat dishes. The Citrus fruits are believed to have been imported to Europe in the Middle Ages and in the Renaissance period. A large number of hybrids have been breed for human consumption. Citrus plants, such as the Orange plant, are easily grown from seed in warm countries, as well as greenhouses and window sills in colder climate.