The kiwi (Actinidia) belongs to the Actinidiaceae family. The fruits are mostly imported from New Zealand, but originate from China. This is also where its actual name “Chinese gooseberry” comes from. The name “Kiwi”, reminiscent of the New Zealand heraldic animal, the small bird, was created for marketing purposes. The kiwi has been known in our country for 30 years and has been one of the most popular exotic fruits ever since.
Various species belong to the genus of kiwis, but most of them are simply called kiwi. The most common are the large hairy kiwis (Actinidia deliciosa), the slightly less acidic, smooth-shelled Actinidia chinensis with yellow flesh and the kiwi berries, also known as mini kiwis (Actinidia arguta). Kiwis have been cultivated in Asia for over a thousand years – not least because of their long shoots, which were used for paper production. The heat-needy and frost-sensitive fruit can also be cultivated here, but the cultivation of the large-fruity kiwis is only recommended in wine-growing regions and in locations with mild winters and rainy summers.
Appearance and growth
Kiwis are perennial, deciduous climbing plants growing like lianas. The large, wheel-shaped flowers of the kiwi plant appear from June to July. Its flowers have snow-white and later yellowish petals with numerous golden-yellow stamens. The plants are dioecious except for a few new cultivars, so they bear either purely male or purely female flowers. You can distinguish between male and female flowers by their shape: Numerous stamens and small pistils distinguish male flowers, while female flowers appear in small numbers per inflorescence and carry radiating white pistils, surrounded by a wreath of stamens. The fruits develop only from the female plants.
The fruits of the kiwi are large, cylindrical berries, depending on the variety, which are covered with a brown and densely haired skin. Inside the fruit there are many intergrown seed containers with black seeds along the central axis. The flesh is green and soft. It tastes sour, aromatic, especially when the fruits are fully ripe but not overripe. Kiwifruit have a high vitamin C content. Since the plants loop like lianas in height and width, they need a supporting structure along which they can grow.
Location and soil
Kiwifruit have a low frost hardness and the shoots are very susceptible to late frost. Even in warm regions or vineyards, kiwis thrive best in a place sheltered from the wind. The location must be warm and bright, but not fully sunny. At locations outside fruit and wine growing areas, the kiwi plants are placed on a southwest wall or west side of the house. So you can delay the budding in spring until the danger of late frost is over. A loose soil rich in nutrients and humus with a pH value in the slightly acidic range is best suited. Soils rich in limestone are poorly tolerated by the kiwi. If necessary, some rhododendron earth can also be added to the soil. If the soil is too poor, you should improve it in advance with compost. Kiwi plants are also suitable for large plant pots on the terrace.
Since kiwi plants grown from seeds only bloom after six to ten years, it is advisable to buy young plants from specialist retailers. These were mostly propagated by cuttings and bloom so already after two to four years.
Kiwis are endangered by late frost – the ideal planting season is therefore from mid-May to August. Since kiwifruit are dioecious, they should always plant male and female plants to ensure fertilisation. The optimum planting distance is three to four metres. It is recommended that as much leaf or bark compost as possible be worked into the soil as preparation and that the young plants be well watered afterwards. It ensures that the soil does not dry out so quickly and does not heat up so quickly in dry periods. The tendrils of the kiwi plants, which can grow up to ten metres long, require a stable climbing frame, such as a pergola or trellis (see “Training and pruning”).
In order for the fruit to ripen and develop its aromatic and sour sweetness, kiwis must be watered regularly, especially in hot summers. You don’t have to fertilize young plants. Older people can be supplied with horn meal or mineral fertilizer in August and spring. During the first few years you should also cover the stems and root area of the kiwi plants with brushwood in winter. If you keep kiwis in a pot, an adequate supply of water and nutrients is essential. You should also prune shoots that are too long regularly.
Education and editing
Since the kiwi forms long shoots, the plants need a stable climbing frame. A trellis scaffold with two to three horizontally tensioned wires is recommended. If the plants are grown on the house wall, you can erect this simple scaffold directly in front of it and attach the shoots to it. The lowest wire should be about 80 centimetres high, the next should be stretched at a distance of 50 centimetres.
Also suitable as scaffolding are arbours or pergolas to which the side shoots of the kiwi plants are attached. During the first few years, a main shoot should be pulled vertically from the trunk to the top wire. From this main shoot, two strong side arms are pulled horizontally to the left and right and the fruit-bearing branches are laid over the wires. Over the years, the liana-like growing plants condense over the trellis or pergola and also offer a beautiful screen. An additional advantage is that large-fruited kiwis can get stuck there for a long time in autumn. Cutting measures are necessary from about the third year. The annual fruit shoots can be shortened by about a third in August, leaving about six to eight leaves. You can also shorten the drive ends of the guide drives once a year. Do more pruning in late summer, as the plants bleed heavily in spring.
Most kiwi varieties are dioecious. This means that each plant carries either only female or only male flowers. At least one male and one female kiwi plant are therefore required for fertilisation. A male plant can fertilise up to seven female plants if the planting distance is not too far (preferably not more than four metres). There are now also a few monoecious kiwi varieties that carry male and female flowers on a plant. Theoretically, you can do without fertiliser. Practice has shown, however, that even with these varieties the fruit set is considerably higher if two plants are placed next to each other. If bees, bumble bees and other insects are absent during flowering, you should take the pollination into your own hands. To do this, carefully stroke the stamens of a male flower over the ray-shaped white stylus in the middle of the female flowers.
Harvesting and recycling
Kiwifruit contains a lot of vitamin C and is rich in calcium, iron, potassium, other minerals as well as vitamins B1 and E. The fruits are also high in fibre and low in calories. The sweet-sour fruits, which from a botanical point of view are berries, can be harvested from the end of September until October. As they often do not ripen completely in cooler locations on the plant, the fruits can simply be left to ripen in the house on the windowsill. Harvest maturity Kiwis unfortunately do not last too long. However, they can be stored quite well in a humid room with a temperature of 12 degrees Celsius. You can eat the vitamin-rich kiwis fresh, but also process them into jams and jellies, boil them down or use them for cakes or bowls.
Although most kiwi varieties are hardy in winter, frost protection is always advisable for young, freshly planted seedlings in the first winter. If kiwis are cultivated in tubs, they should be kept in a cool, light location indoors throughout the winter because of their frost-sensitive roots. With the beginning of the shoot in March, the plant is returned to the open air. Short-term sub-zero temperatures can be tolerated even without winter protection.
Hayward’ is a proven variety with large, hairy fruits. Your kiwis will be up to seven centimeters long and about 100 grams heavy. They should be harvested after the first light frosts at the latest. The plants bear from about the fourth year and need a fertiliser variety because they are dioecious. Equally popular are ‘Bruno’ with narrow and cylindrical fruits and ‘Monty’. Abbott’ grows strongly, blooms early and is a purely female variety. From the end of October their cylindrical, medium-sized fruits are ripe and taste very sweet. Matua and Nostino are male fertilizers.
The kiwi variety ‘Jenny’ is a very productive and self-fruiting breed. Their fruits are up to four centimetres in length and are smaller than those of ‘Hayward’, weighing about 20 grams. The very sweet, juicy fruits are ready for harvest from mid-October. They usually ripen in the winegrowing climate on the shrub, in climatically less favourable locations they are left to ripen in the house. Tip: ‘Jenny’ is also suitable as a fertiliser for large-fruited dioecious kiwi varieties such as ‘Hayward’. But: Even if it is a self-pollinated breeding, it carries more richly if one places a male planting partner at its side. Mini-Kiwis originate from the wild species Actinidia arguta. They are harder to freeze and require less heat than large fruit varieties. The high-yielding plants form smooth-shelled fruits that can be eaten unpeeled directly from the shrub. A proven variety is, for example, ‘Weiki’, which was bred at the Weihenstephan Research Station and is therefore also called ‘Bavarian kiwi’. Like the well-known male variety ‘Kiwai’, it is the result of selections from Actinidia arguta and Actinidia melanandra. Weiki’ forms walnut-sized, sweet and very vitamin C-rich fruits that ripen from the end of September. It is resistant to pests and diseases and yields up to 30 kilograms. A male variety is required to fertilise the flowers. The variety ‘Issai’ is a self-fertile mini kiwi. The strongly growing climbing shrub can grow up to 18 metres high and is extremely frost hardy. The yield already starts after two to three years. Its smooth, green fruits are up to four centimetres long, taste very sweet and develop a pleasant aroma.
Kiwi plants are propagated by cuttings. In early summer, cut shoots about 15 centimetres long, at least pencil-thick, with already woody bark and three to four clearly visible eyes. Remove all but a few leaves at the tip of the shoot and place the sections in pots filled with lean growing soil. Lower the vessels into the ground in a shady, wind-protected place and cover the surface with a thick mulch layer of straw. Once the cuttings have rooted through the pot, they are planted in the intended place.
Diseases and pests
Kiwi plants are generally very robust. Occasionally, aphids or scale insects occur, rarely fungal diseases.
Whether potted plants such as oleanders or indoor plants such as orchids: The scale insect infests the most diverse plants. René Wadas, a herbalist, will give you his tips on pest prevention and control: Production: Folkert Siemens; Camera: Fabian Primsch; Editing: Dennis Fuhro; Photo: Flora Press/Thomas Lohrer
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I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.