Trifoliate orange

The trifoliate orange, Poncirus trifoliata or Citrus trifoliata, is a member of the family Rutaceae. Whether the species should be considered to belong to its own genus, Poncirus or included in the genus Citrus is debated. The species is unusual among citrus for having deciduous, compound leaves and pubescent (downy) fruit. The trifolate orange was long viewed as the sole member of Poncirus, until the discovery of a second species, Poncirus polyandra, in Yunnan (China) in the 1980s. It is native to northern China and Korea, and is also known as the Japanese bitter-orange, hardy orange or Chinese bitter orange. The plant is a fairly cold-hardy citrus (USDA zone 6) and will tolerate moderate frost and snow, making a large shrub or small tree 4–8 m tall. Because of its relative hardiness, citrus grafted onto Citrus trifoliata are usually hardier than when grown on their own roots.