Native to China and Korea, this is the most cold hardy
Trifoliate orange and various hybrids of this plant are widely used as citrus rootstocks. 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.
Recent studies have revealed that the trifoliate orange contains aurapten at a high concentration, which is one of the functional components having immunity against citrus tristeza virus (CTV).
he fruits are very bitter, due in part to their poncirin content. Most people consider them inedible fresh, but they can be made into marmalade. When dried and powdered, they can be used as a condiment.
The fruits of the trifoliate orange are widely used in medical traditions of East Asia as a treatment for allergic inflammation.
