The mandarin orange is a small citrus tree with fruit resembling other oranges, but smaller and oblate, rather than spherical like the common oranges. It is a mid-sized tree, usually not exceeding 4 m (13 ft) in height, with small leaves shiny and green and flowers borne singly or in small groups. The plant is sensitive to prolonged and/or extreme cold and is therefore limited outdoors to tropical, sub-tropical and the warmer parts of warm temperate climates. In regions with cooler climates, potted plants are brought into a greenhouse, conservatory, or indoors as a houseplant during the winter periods.