Trifoliate Orange: Who's the Hardiest of them All? The hardiest citrus of all is the Trifoliate orange ( Poncirus trifoliata or Citrus trifoliata ). It is a deciduous citrus from central China, adapted to cold winters. In the United States, it is hardy to parts of Massachusetts west to about St. Louis, MO. In Georgia, it is hardy throughout the state, of course. It is definitely an heirloom plant and was frequently planted many years ago. The ripe fruit have a distinctive odor (which I find very pleasant) and many years ago, people picked the fruit in the fall and placed it in bowls inside. At that time, many people called the Trifoliate orange a "smell lemon." Because it was commonly planted and easy to grow in the South, the Trifoliate orange escaped cultivation and naturalized in many areas throughout the state (particularly the Lower Piedmont). Trifoliate orange is strongly adapted to floodplains, particularly those with sandy soil. In the Piedmont, it is extr