Trifoliate orange, also known as Poncirus trifoliata or Citrus trifoliata, is a thorny shrub bearing round, green fruits resembling small oranges. It is a hardy plant found in various regions including China, Korea, and Japan. While the name "trifoliate orange" is popularly used, there are other synonyms commonly used for this plant. These include bitter orange, Japanese bitter orange, hardy orange, and Chinese bitter orange. The name "bitter orange" stems from its sour taste and the fact that it is not typically consumed as a food. Regardless of its name, this plant is widely used for ornamental purposes or as a rootstock for citrus plants.