The oval fruits of a plant of Chinese origin are commonly called kiwis, whose botanical name is actinidia deliciosa, or actinidia chinensis; these plants are widespread in Asia, and in particular in China, where the fruit has been used by man for centuries. In China there are not many cultivations of this type, as the availability of plants in the wild makes cultivation by man useless; only at the beginning of the 1900s the cultivation of this fruit for decorative purposes first began, by a New Zealand teacher, who took seeds of these plants in China, and took them home. Since then the history of kiwifruit has traveled the globe, reaching Europe in the late 1900s. Today the country that cultivates the largest quantities of kiwifruit in the world is Italy, followed by New Zealand, France and Chile and from a few other nations. Initially, cultivation in Italy began in Trentino, in areas where traditionally only plums and apples were grown; today there are also cultivations in Lazio, Friuli and Veneto.
From a botanical point of view, the actinidia is a liana, or a climbing shrub, which produces thin stems able to cling to any support; in Italy hybrids are grown, derived from actinidia deliciosa, which are bred like vines, to form rows. They have thin stems, with dark bark, and large oval or cordiform, deciduous leaves.
The fruits of actinidia deliciosa have a brown, pelosetta peel, with a high tannin content, which makes it inedible; the pulp is green, dotted with small dark seeds, which attach themselves with filaments to a lighter fleshy part that runs through the center of the fruit. In Asia there are other species, for example actinidia chinensis has yellow flesh, but there are also fruits with orange or pink flesh; for some strange reason the horticultural varieties with fruits with pulp of more usual color for a fruit, therefore not green, have not had the same success on the European tables; for this reason in Italy mainly varieties derived from kiwifruit with green pulp are cultivated.
These plants originate from areas of the world that have a quite different climate from the Mediterranean one; what they need to develop is good humidity, and very hot summers.
In fact, to overcome the summer drought, in Italy the kiwis are irrigated during the summer, and in areas with a particularly dry climate, it is preferred to plant the plants in a semi-shaded area, in order to protect them from the scorching sun in the hot summer days. In addition to this, to keep the soil fairly wet and cool, we tend to mulch it, throughout the year, so as to keep part of the moisture near the foot of the plants.
In general they do not fear frost, even if intense, even if occasional late snowfalls, or very intense frosts, cause the decay of the older branches, and can cause years without fruit.
Kiwis, as we all know by now, are dioecious plants, that is, male flowers and female flowers bloom on distinct plants; to obtain a good harvest it is generally advisable to have at least one male specimen, every 3-4 female specimens, obviously planted close.
The fruits are produced on the branches of the previous year, it is therefore important that the pruning does not go to remove all the old vegetation; generally the weaker and thinner branches are pruned, and the more vigorous branches are maintained with about 5-6 buds. Proceed in autumn or winter, after having collected the fruits: the branches that have brought fruit are shortened, and the branches that have not brought them are allowed to develop, eventually shortening them slightly.
A second pruning can be practiced when the plant is in full vegetation, in summer, to lighten the foliage, which often becomes very thick, and to remove part of the fruit, if they were in excessive quantity.
In practice we continue to stimulate the development of new branches, to the detriment of the old ones, in continuous renewal of the plant; this is because the old branches tend to stop flowering, and therefore to bear fruit.
The reduction in the number of buds does not help to increase production, but on the contrary to decrease the number of fruits per plant, because a large number of kiwis on a shrub, means to get very small fruits, and an excessive commitment to the plant.
These are very vigorous climbing plants, so in addition to pruning, which serves as a control of shrub development, it is essential to water in case of drought, from May until September, and to fertilize the shrubs periodically; it is therefore supplied with manure in the autumn, planting it slightly at the feet of the plants, and granular slow-release fertilizer at the end of winter.
The kiwis in the orchard
To better cultivate kiwis it is therefore advisable to place them in a bright area of the orchard, with at least a few hours of sunshine each day; the amount of hours of sunshine we can keep these plants depends on the climate of the place where we live: in the south it is advisable to keep these plants in a semi-shaded area of the orchard; the more you climb to the north, the more advisable to move the specimens to a more sunny area.
They are climbing plants, very vigorous, if left to develop without control they can also become invasive; also well-cultivated and pruned kiwis need a good scaffolding of the rows, so that they can form large pergolas; in this way the vegetation of the plants will shade the foot of the plants; the fruits will dangle below the pergola, so that they can be picked up more quickly.