Citrus fruits are evergreen plants of Asian origin; in the areas of origin they enjoy hot and humid summers, and fairly mild winters, with minimum temperatures generally never below zero degrees.
For this reason cultivation in Italy is widespread only in areas with a mild climate; Lemons prefer winter temperatures no lower than -3 / -4 ° C, other citrus fruits, such as Kumquats, can withstand even much more rigid temperatures, close to -10 ° C.
To promote resistance to cold it is possible to graft citrus fruits on Poncirus trifoliata plants, a Rutacea rustic with deciduous leaves: in this way Orange or Mandarin plants can also be cultivated in areas of Central Italy. In fact, the rusticity of some plants indicates only the minimum temperature at which they can survive: we want to remember that a rustic plant up to -10 ° C, survives without problems at this temperature only if reached gradually, after a period of several weeks at low temperatures ; a sudden frost, with sudden drops in temperature, can cause serious damage.
In addition, plants grown in cold climates do not always produce fruit, or sometimes give poor, or low quality, crops. Even in Sicilian areas it can happen that sudden low autumn temperatures cause the loss of a large part of the harvest.
So we grow citrus fruits in a sunny and sheltered from the wind, and, if we live in areas with harsh winters, let us put them in a container, so that we can move them to a cold greenhouse in case of very low temperatures, or remember to cover them with non-woven fabric during the winter.
Citrus fruits grown for fruits are evergreen plants; they bloom in spring, and some species have a second flowering in late summer or autumn, the flowers are white and intensely scented; the fruits ripen in the autumn and winter period; there are many hybrids, with different flowering and fruiting periods, so that the production can cover many months. Most of the lemon hybrids have more blooms a year, so that the production of lemons can cover practically all year; moreover, while all the fruits of the citrus fruit must necessarily ripen on the tree, otherwise once harvested the maturation stops, in the case of the lemons the maturation continues even after harvest.
They are fairly easy to grow plants; they need soft and medium rich soil in organic matter, very well drained and not excessively clayey; generally two parts of peat are used, two parts of garden soil and a part of sand, adding some handfuls of lapillus or pumice stone. All the species, except the mandarin, do not have a rest period, therefore they need regular watering throughout the year: we water abundantly, but avoiding stagnation and always waiting for the soil to dry well between watering and the other one.
Every 3-4 months we add to the soil some mature manure, or granular slow release fertilizer; in the cultivation of citrus fruits lupine powder is used as a soil improver, which seems to guarantee excellent results, it is added to the soil in quantities of some handfuls per square meter, every 3-4 months.
Citrus fruits: Botanical names
We list the most often used botanical names for citrus fruits commonly on the market; not all names are certain, since not all authors agree in considering some original or hybrid species. Then there are every kind of very numerous hybrids and cultivars, with more varied names, such as the famous Tarocco or Navel oranges.
Citrus x sinensis: Orange
Citrus x limon: Lemon
Citrus maxima: Pummelo
Citrus medica: Cedar
Citrus aurantifolia: Lime
Citrus reticulata: Mandarancio
Citrus x bergamia: Bergamot
Citrus aurantium: Bitter orange
Citrus x paradisi: Grapefruit
Citrus x nobilis: Mandarin
Citrus x clementine: Clementine (seedless mandarancio)
Fortunella margarita: Kumquat
Citrus myrtifolia: Chinotto.