The Citrus genus includes numerous species of evergreen trees or shrubs, of medium to slow growth, reaching medium (or medium-small) dimensions. They are extremely popular because of the beautiful foliage, often aromatic, the white flowers which are almost always very fragrant and the edible fruit commonly known as “Citrus Fruits”. Native to south-east Asia where they were probably grown 4000 years ago. In Tuscany they began to be used as ornamental plants at the time of the Renaissance when they were grown in large terracotta tubs from Impruneta and were an important element in the decoration of the gardens of the Medici family. Today Citrus plants are sold all over Europe despite their vulnerability in cold temperatures which means they can only be grown in open ground in zone 9 and above, in sunny positions. In less suitable climates they can be grown in tubs, usually very ornamental, and are brought outside only during the warm season. During the cold months they must be taken under cover and kept at a temperature between 4°C and 10°C. Citrus plants have a fairly superficial and spreading root system and therefore require moist, not calcareous soil. The thin bark of the branches and foliage are not made for withstanding long periods of drought. It is therefore necessary to give abundant water frequently in summer but in winter once a week or less is sufficient.