Poncirus trifoliata

Trifoliate orange, Japanese bitter orange. A large spiny shrub to 7m (22 ft) high, though often less; closely related to the Citrus family. Bears yellow or orange fruits 1-2″ (3-5 cm) in diameter (freely borne in SW Britain), the juice of which can be used as a lemon substitute; young leaves have also been eaten cooked. A good hedging plant (stockproof; needs sheltered position in Britain) and a bee plant. Needs sun. Growth 2m (7 ft) in 10 years; hardy to -23°C.