The lowest temperature of vines in winter mainly considers the cold resistance of roots. Generally speaking, grapes in Europe have the worst cold resistance, but pears are different. The roots are frozen at-13℃, because the roots of grapes are the least cold-resistant, such as rose dew, while the branches and buds have stronger cold resistance, and the roots are frozen at -6℃ ~-8℃. Therefore, when the roots are frozen at -4℃, the cold resistance of European and American hybrids is slightly stronger than that of European species. American grape has strong cold resistance, and its freezing injury first occurs in the root system.