Kiwi is a plant of Chinese origin, which is well suited to cultivation in central and northern Italy; it is a vigorous climber, with a deciduous leaf, which needs support to develop, it is therefore essential to plant the plants near a wall, a row or a pergola: being the plant very vigorous and luxuriant we prepare structures solid support, to prevent heavy branches from ruining them over the years. The kiwis prefer semi-shady positions, as they fear prolonged drought; it is also advisable to place them in a place not subject to strong winds, which, in addition to drying out the soil, can cause damage to the branches. These are dioecious plants, where female and male flowers are separated on different plants; to obtain fruits it is therefore necessary to have some female specimens and at least one male specimen. The growing medium should preferably be neutral or acid, they fear the presence of limestone in the soil; before placing the young plants at home we enrich the soil with peat and manure, and also with small amounts of sand, which improves drainage. Pruning is practiced after harvesting, in late autumn, removing the branches that have borne fruit; for very vigorous specimens it is good to also practice the green pruning, after flowering, shortening the branches that do not bear buds or small fruits, so as to better aerate the entire foliage. After planting the young plants water the soil well; then we water only if and when the soil is dry, avoiding excesses. During the summer months we water more regularly. To avoid overheating and to better maintain humidity on the foliage of the plants it is of great benefit to repair the plants with shading nets during the hottest months of the year.
Origins and spread of the kiwi
The fruit commonly known as kiwi is produced from a plant originating in China whose real name is Actinidia chinensis and which belongs to the actinidiaceae family. It is a climbing plant coming from the mountain environments of that country. The cultivation of this vegetable has spread all over the world since 1970. At first it became very common in New Zealand (where it was given the current commercial name in reference to a bird). Since the 1980s it has also spread to the American continent and Europe. The countries where production has become very massive soon are: Italy, New Zealand, Chile, Brazil, France and Greece.
In our country the regions most voted for kiwis are Lazio, Piedmont, Campania and Veneto.
It is a very vigorous climbing plant. It bears alternate leaves, simple, round and deciduous. The upper page is of a rather dark green while the lower one is lighter, with brown shades and slightly pelosetta. The edge is jagged and the length of the leaf can go from 10 to 30 centimeters. The flowers are apical. Some varieties are dioecious, others bear hermaphrodite inflorescences. In any case, they are equipped with 5 sepals and 5 petals (cream white).
The fruit is an elliptical berry with a medium brown and hairy peel. The pulp is emerald green (but there are also cultivars with other nuances) and contains numerous small black oval-shaped seeds. The fruits begin to be ripe (depending on the region) from mid-October to early November. The pulp is found around a lighter central column whose size varies according to the cultivar. Both parts are edible.
The kiwi must be planted in areas with a temperate climate. It is particularly important that it is placed in areas protected from strong winds: these in fact could cause the fall of flowers and small fruits as well as being an obstacle to the work of pollination of bees.
In order for there to be good production in the summer, at least 25 ° C must be reached. In winter, however, it should not fall below -10 ° C. Tolerance to cold is considerably conditioned by the age of the specimens and also by the environmental humidity.
It is very important that humidity is at least 60% during the growing season. In addition, in spring and summer, rainfall (or irrigation) must be abundant. This is why, especially where the cultivations are intensive, drip irrigation systems are set up and the leaves are often also vaporized. This treatment has the purpose (especially during the summer and when it is very hot) of avoiding overheating and excessive evaporation of liquids. The very large leaves in fact suffer frequently due to this inconvenience.
Kiwi cultivation requires very deep, well-drained, permeable and rich in organic matter substrates. If our soil is very compact, it will be good to replace that portion with a more aerated compound before planting and to prepare a thick draining layer on the bottom of the hole.
The ideal soil is sub-acid (with a pH between 6 and 7), rich, but not excessively calcium and above all free of chlorine to which the kiwi is particularly sensitive.
The varieties that can be most easily found on the market are Hayward, Abbot, Allison, Bruno, Katuscia, Top star, Tumuri, Matua. Before planting, you need to get specific information on the qualities of the individual cultivars to find out which are the most suitable for our soil and our climatic characteristics.
Hayward is very widespread in large plantations. In fact, this has the undoubted advantage of tolerating refrigeration well. The fruits are usually harvested when they are still immature and then placed in refrigerated cells where they can remain until the following year. To force maturation they are exposed to ethylene or transferred to the same rooms where apples are stored.
In Italy the most used rootstock is the Bruno variety, while abroad seedlings of the Hayward variety are often used abroad.
To make the planting optimal it is necessary to carry out a whole series of tillage operations. First of all it must be leveled at its best and all the weeds must be eliminated. You must then dig a hole at least 50 cm deep. On the bottom you will have to make a drainage layer with gravel. We will proceed with the basic fertilization. Once the plant is inserted, the roots will be covered with the earth taken. If this turns out to be too compact it will be good to mix it with gravel or sand or replace it completely with a product suitable for fruit plants.
The ideal period for this work goes from autumn to spring, avoiding the months when there are frosts.
How to structure a kiwi cultivation
Kiwifruit is a vegetable that needs supporting structures in order to develop better. There are different types of media possible. Depending on our needs we can make the plant climb on pergolas built with cement and wire poles, or use complexes of elements specifically for sale. Among these it is very common the T system with a vertical pole on which a horizontal one is supported from which the wires that will act as support are doparted. The plants will develop their shoots above, horizontally. Usually the set has a height of 6-1.8 meters. Generally they are interspersed with taller poles on which some shading sheets will then be laid to be used during the summer to avoid excessive evaporation.
Between one row and the other the average distance goes from 3 to 5 meters, in the row instead it is about 2-4. The male specimens are put in alternate rows and the ideal is that there is at least one every 5 females.
The water needs of the actinidia are very high especially when we are talking about young and recently planted specimens: the roots are rather superficial and their volume is scarce compared to the width of the foliage and the leaf surface exposed to light.
In this sense it will be very important to start irrigating very early and with a certain regularity. In the absence of heavy rainfall it may be necessary to intervene every day.
For this reason, very extensive plantations are almost always equipped with underground irrigation systems to which special mechanisms are installed to vaporize the foliage during the hottest hours of the day.
The ideal exposure for the kiwi is full sun. In some periods of the year, however, especially during the months of July and August, the heat can be excessive and therefore deprive the plant of the necessary hydration. For this reason, slightly shaded sheets are placed above the cultivations.
Actinidia, in order to produce well, requires large amounts of various types of nutrients.
It must be pointed out that the crucial element for having good growth and good fruiting is nitrogen. It must always be given in abundance, throughout the growing season, but especially at the time of harvest and after this has occurred. In this way the plant will be able to restore the stocks that have been lost and will prepare for growth for the following year.
Phosphorus and above all potassium are also important, which has a decisive influence on the size and taste of the fruit.
If chlorosis appears it may be useful to administer chelated iron.
The first few years a training pruning must be carried out in order to obtain a trunk from which two arms develop to cover the entire horizontal part of the support.
Pruning to obtain good fruiting, on the other hand, must be done twice a year, once in winter and once in summer. The winter one must leave three well-developed side secondary branches for every meter of horizontal branch.
Summer pruning, on the other hand, must tend to improve ventilation and exposure. The badly developed and dry branches are therefore eliminated. This pruning is done twice, before and after flowering, generally in the months of April and June. In this last phase, deformed flowers are also eliminated and only the best-formed ones are left. We will then intervene again to make a selection of fruit trees.
Usually you can start harvesting from the third year on from the plant. Full productivity is usually reached during the eighth season and the average production at that point will be around 20000 kg per hectare.
Growing kiwis: pests and diseases
Actinidia has been a fairly healthy plant in Italy to date. In fact it was rarely necessary to resort to treatments and it was commonly cultivated under the organic regime.
Unfortunately in recent years it has been hit by a rather important disease: bacteriosis.
The first symptoms are the appearance of honey-like drops that over time take on a reddish color. Below the affected shoots there are areas that appear visibly rotten, of an intense brown color.
Unfortunately, there are few remedies except that of eliminating all the branches struck at the base or cutting the specimen. In extreme cases you can also be forced to totally remove the tree. All that results from the cuts must be incinerated.
To prevent it is important to carefully sterilize the shears before pruning and before moving from one plant to another. After cutting, always use mastics with copper additives.
In areas where the infestation is extensive it is better to avoid using bees for pollination because they could be a vehicle of contagion.
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