Normally, citrus trees are killed by even brief freezes. The article discusses a number of methods used by the Soviet Union to grow 200,000 tonnes of citrus fru

Normally, citrus trees are killed by even brief freezes. The article discusses a number of methods used by the Soviet Union to grow 200,000 tonnes of citrus fruit per year, in places where winter temperatures dropped to -30 C and the ground froze 50 cm (20 inches). They developed some interesting new plant varieties and cultivation methods (some very labor intensive).