OLIVE TREES HAVE GREAT RESISTANCE to disease and can endure harsher weather conditions than many other fruits of the Mediterranean region. It is true, however, that temperate climates, characterized by warm, dry summers and rainy winters, favor good harvests. according to Italian folk tradition, there are five factors that create the ideal conditions for the olive tree : sun, stone, drought, silence, and solitude. Italy and Spain are now the world's biggest producers of olive oil. There are about thirty varieties of olives growing in Italy today, and each yields an oil with its own unique characteristics.