The Poncirus tree (Poncirus trifoliata) (탱자나무), also known as the trifoliate orange, has a couple significant representatives in Gangwha-do, Ganghwa-gun, Incheon. These trees are near the northern limit of their range. Poncirus were planted here (page in Korean) because they form a thorny barrier to invaders, of which Ganghwa-do has had its share.

• Poncirus tree of Gapgot-ri (also [1] in Korean)
  • The tree's address: 1016, Gapgot-ri, Ganghwa-eup Ganghwa-gun Incheon
  • Classification: Natural Monument No. 78.
  • Age: 400 years
  • Height: 4 metres
  • Circumference: 1 metre.

• Poncirus tree of Sagi-ri (also [2] in Korean)
  • The tree's address: 135-10, Sagi-ri, Hwado-myeon Ganghwa-gun Incheon
  • Classification: Natural Monument No. 79.
  • Age: 400 years
  • Height: 3.8 metres