Citrus is a popular name of about 20-25 species of fruits growing in Asia, Australia and the islands of the south-western Pacific. These plants thrive in tropical and subtropical climates, however, they are known and appreciated all over the world. The first documents certifying cultivation of citrus fruits come from China and are more than 4000 years old! Nevertheless, citrus trees grew for a long time only in the eastern hemisphere and they appeared in the west only in the nineteenth and twentieth centuries brought by gardening enthusiasts. Today, many people grow these plants even in cooler climates, putting pots with trees in warm places during colder seasons.