The kiwi cultivation is highly appreciated worldwide. This fruit, also known as actinidia, is usually planted far from frost and harvested in the autumnal period. Today, we will explore the characteristics of the kiwi plant, the main varieties available in the market, and explain how to distinguish male from female plants. We will then discover how to cultivate kiwis in home orchards, using key techniques of organic cultivation.
Finally, we will discuss how and when to perform the kiwi pruning, a delicate and essential operation to increase the productivity of our plants.
The Origins of Kiwi
The kiwi, scientifically known as Actinidia chinensis or Actinidia deliciosa, is a fruit-bearing plant belonging to the Actinidiaceae family, Actinidia genus.
This cultivar is native to China, particularly the valleys of the Yangtze River, the longest river in Asia and the fourth-longest in the world. It grows spontaneously in these regions.
However, the name’s origin is not Chinese but rather New Zealandish, the country where the plant was exported in the early 20th century. The kiwi, in fact, is also a flightless bird, the symbol of New Zealand itself.
Kiwi in Italy
Kiwi cultivation in Italy began in the 1970s and quickly spread to the regions of Central and Northern Italy (as well as throughout the country). The regions with the highest concentration of production are Lazio, Piedmont, and Veneto.
The success of its spread in our beautiful country is such that Italy is now the world’s second-largest kiwi producer, after China.
Now let’s take a closer look at the structure of the kiwi plant.
The Kiwi Plant
The actinidia plant presents itself as a climbing vine that can reach considerable dimensions. In terms of height, it can grow up to 10 meters.
As a climbing plant, kiwi cultivation requires supports. It also needs to be anchored to these supports for orderly growth. In nature, it finds support in trees or cliffs, for example. For this reason, the most common form of cultivation for kiwis is through pergolas, which are easy to build even in a domestic setting.
Kiwi is a deciduous plant, meaning it loses its leaves during the autumn period.
The leaves of the actinidia resemble a heart shape, rounded, with a pointed tip and toothed margins.
The Trunk and Branches
The main trunk of the plant and the older branches have a rough bark with a brownish hue. Numerous branches develop from here.
The young shoots are very tender and have an herbaceous consistency. They are also covered with fine reddish hair, as are the leaf and flower stalks.
Kiwi cultivation allows for abundant fruiting. However, some precautions must be taken to ensure correct cultivation. One important characteristic of actinidia is that it is a dioecious plant.
This means that there are female kiwi plants, which bear fruit, and male kiwi plants, which do not fruit but are essential for pollination.
The identification of the kiwi plant’s gender is possible through observing its flowers.
Female flowers are unique, very large, and white. They are also spaced well apart to allow fruit formation.
Male flowers, on the other hand, are usually clustered together. They have a cream color, slightly different from the female flowers. Additionally, they are smaller in size, and the inside of the flower is well visible.
To perform their pollination function, male flowers produce abundant pollen, but they have deformed ovaries.
Flowering and Pollination of the Kiwi Plant
The kiwi flowering period extends from early May to early June.
Pollination of the female plant can occur in two ways: through wind (known as anemophilous pollination) or with the help of bees and other pollinating insects (entomophilous pollination).
As mentioned, excellent pollination is essential to ensure a good level of both quantity and quality of the production. Therefore, in kiwi cultivation, the presence of both female and male actinidia plants is necessary. A good numerical ratio is one male plant for every 5-6 female plants, distributed evenly. This way, abundant production will be guaranteed.
The Kiwi Fruit
The kiwi, as a fruit, is a fleshy berry with a slightly oval shape and brown color. The skin is covered with very fine hair.
The flesh inside is a bright green color, firm, sweet, and slightly tart. There are also kiwi varieties with yellow or reddish pulp.
The interior of the fruit is dotted with tiny seeds, usually black, barely noticeable when eaten. The seeds are arranged in a crown around the white heart, called the columella.
Main Varieties of Kiwi
In our country, the most widespread kiwi variety is Hayward. The characteristics of this species include great sweetness and excellent fruit size, high adaptability to different cultivation conditions, and excellent productivity.
Other well-known varieties include Abbot, Allison, Bruno, Katuscia, Top star, Tumuri, Matua, Autari, M3. As rootstock, the most used is that of the Bruno variety.
Kiwi cultivation originates from Asia, but it has adapted well to the climatic conditions of our latitudes. It is grown from north to south and can also be planted in a home garden. Of course, its cultivation requires proper care. Let’s see what they are.
Kiwi cultivation prefers sub-acidic soils, with a pH between 6 and 7, and with a reduced content of active limestone (i.e., with a pH higher than 7). Limestone-rich soil can lead to problems of iron chlorosis, which is abnormal yellowing of the leaves. This is generally due to the difficulty for the leaves to absorb iron. In organic farming, this deficiency is resolved by adding organic matter and increasing the humus content, a natural iron binder, in the cultivation soil.
Ideal Growth Climate
Kiwi prefers a temperate climate as it is sensitive to frost, especially during the budding phase. In terms of exposure, it is best to plant the kiwi in a sunny area. At the same time, it should be sheltered from the wind, which could break the long branches. Windbreaks can be used to overcome this problem.
During the summer, excessive exposure to the sun can lead to dehydration of the plant. Therefore, it should be protected with appropriate shading nets. Of course, we are talking about extreme weather conditions.
Kiwi cultivation is usually propagated using grafted plants, whose sex expression is already known, and can be planted at two different times of the year: either at the beginning of autumn, long before the probable frosts, or at the beginning of spring, with the risk of frost already averted.
The optimal planting process is carried out in multiple steps. First, the soil is worked, removing weeds. Then, a hole at least 50 cm deep is dug, and gravel is placed at the bottom to improve drainage. At this point, organic fertilizer is applied to the bottom and the plant is placed in the hole, covering it with the previously removed soil.
The optimal technique for managing the soil for growing kiwi is permanent inter-row cultivation. With this technique, weed control is achieved by favoring the calculated development of a grass cover, for example, using grasses. This cover will be regularly mowed and should not exceed 10-15 cm in height.
Inter-row cultivation helps maintain good soil structure, adds organic matter, and limits soil compaction. It also reduces risks for the plant, as kiwi roots are very shallow, and soil tillage could cause damage.
Kiwi cultivation has high water requirements. Especially during flowering, fruit set, and fruit development stages, the plant needs sufficient water to avoid water stress. Towards the end of the annual cycle, starting from August, water supply should be gradually reduced to maintain fruit quality. However, proper moderation is essential. Waterlogging is detrimental to almost all crops, so ample water is good, but without causing dangerous waterlogging.
The Kiwi Pergola
As mentioned earlier, for proper development, kiwi needs adequate support. In a domestic setting, it’s easy to create a pergola, similar to what is done for vines.
Simply create a square with large wooden poles and run wires on it to create an overhead net on which the kiwi will branch out.
The height of the pergola should be at least 2 meters, with a distance of at least 4-5 meters between each pole.
With the pergola technique, kiwi becomes an ornamental plant for the garden. It is particularly suitable, due to its rapid growth and vigor, for naturally covering medium-sized surfaces and providing pleasant shade during the summer months.
Proper kiwi cultivation also involves the pruning phase. We have already talked about the general rules for correct pruning of fruit trees.
Kiwi pruning is delicate and essential for ensuring abundant and high-quality fruiting. It must be carried out in several stages and serves different purposes. To perform proper pruning, you should have the right tools.
First of all, in the early years of growth, formation pruning is carried out. This aims to develop the main trunk and the necessary branches to cover the support structure.
Once the plant is formed, two other types of pruning are performed: winter pruning, at the end of winter, and summer pruning, in summer.
Winter pruning, or dry pruning, is carried out as soon as the period of severe frost is over, typically from February to March, depending on the region.
With this type of pruning, the previous year’s shoots of the plant are removed, and the current year’s shoots, which will bear fruit next year, are shortened.
Summer pruning is essential for the proper growth of the kiwi plant and involves multiple interventions. It is done twice, just before and just after flowering, usually in April and June. The purpose is to thin and ventilate the canopy, removing poorly developed or dry branches. During the late June pruning, deformed flowers are also removed to achieve better fruiting.
Further intervention is carried out on female plants when the fruits appear, removing any excess or deformed ones.
This operation improves the size and quality of the fruits. Don’t be afraid to do it, as the kiwi plant can yield substantial productivity. It’s worth noting that a single plant can produce up to 30 kg of fruit.
Biological Pest Control
Regarding pests, there are many enemies of kiwi cultivation. Depending on the season, attention must be paid to various symptoms.
Mites and Red Spider Mite
In the summer, particular attention is paid to mites, especially the red spider mite, which usually acts in June and July.
Against this mite, which is very damaging to various crops, a completely natural defense technique involves abundantly spraying the vegetation with cold water. This prevents egg hatching and the emergence of a new generation of mites.
Another sworn enemy of kiwi cultivation is the moth Argyrotaenia pulchellana, better known as Eulia, which is very similar to the tomato leafminer Tuta absoluta.
The moth has three generations per year and overwinters as a pupa hidden in the trunks and branches of the plant; the larvae appear in three different periods: late May, late June-early July, and late August.
The damage caused by the moth includes the damage to leaves and fruit erosion. On actinidia, the larvae of the second generation are particularly dangerous, while damage caused by the third generation is rarer.
Biological defense can be effectively achieved using Bacillus thuringiensis var. kurstaki on larval stages.
To determine the most appropriate timing for intervention, it is advisable to monitor the situation using pheromone-based traps for sexual confusion.
Finally, don’t forget to keep an eye out for the presence of scale insects. If an attack occurs, it is essential to eliminate the affected parts of the plant during pruning. If necessary, you can intervene with washes based on pure Marseille soap and, as a preventive measure, use natural macerates such as fern or nettle.
The kiwi harvest takes place in the full autumn. Depending on the climatic zones, it starts from October and extends to November and December. The fruits detach from the plant very easily; they simply need to be twisted off like small lightbulbs. In supermarkets, kiwis can be found until late spring. This is due to late-ripening varieties and storage techniques in cold rooms. We will also talk about the properties and characteristics of this fruit, one of the richest in vitamin C, in the near future.