Olive Region of the Alps

The great plain of Upper Italy[?] has a winter climate colder than that of the British Islands. The olive and the characteristic shrubs of the northern coasts of the Mediterranean do not thrive in the open air, but the former valuable tree ripens its fruit in sheltered places at the foot of the mountains, and penetrates along the deeper valleys and the shores of the Italian lakes. The evergreen oak is wild on the rocks about the Lake of Garda, and lemons are cultivated on a large scale, with partial protection in winter. The olive has been known to survive severe cold when of short duration, but it cannot be cultivated with success where frosts are prolonged, or where the mean winter temperature falls below 5.5C (42°F); and to produce fruit it requires a heat of at least 24C (75°F) during the day, continued through four or five months of the summer and autumn.