Growing Kiwi Fruit
They’re clever, folk, the New Zealanders. They took a plant that we’d always known as the Chinese gooseberry,deliciosa and discovered that its fruit have just the qualities needed for a commercial crop: they can be eaten in any number of ways, with sweets or savouries, the plants are easy to grow, very hardy, crop abundantly and, most importantly for a faraway country, they store and travel very well. The final touch was to do away with the old name, rechristen them Kiwi fruit and you had the best thing to hit New Zealand since sheep. They caught on in European supermarkets and, of course, gardeners then wanted to grow them at home. And there’s no real reason why they shouldn’t. They are about as hardy as grapevines and are pruned rather similarly too.
HISTORY AND TYPES OF KIWI FRUIT
As its old common name suggests,deliciosa (which you will still sometimes see listed as Actinidia chinensis ) is a Chinese plant, originally seen in the wild by the great plant collector, Robert Fortune, in 1847 although it wasn’t cultivated in the West until the early part of the twentieth century. It was introduced to New Zealand at about the same time but for many years, no one took much interest in it. And although it first began to be grown commercially in New Zealand in the 1930s, its success as a major crop dates from the 1960s. In recent years, a great deal of selection and breeding and also studies of the best cultivation methods have been carried out, but New Zealand no longer has it all its own way and several other countries are now growing Kiwi fruit commercially.
Themust be moist but with no tendency to waterlogging, ideally rich in humus and very slightly acid, although Kiwi fruit will tolerate moderate alkalinity if this is countered with applications of sequestered iron fertilizer. Very heavy or very light soils must be improved with organic matter and as Kiwi fruit are commonly planted against walls, it must be borne in mind that the soil in such positions will normally be quite dry and impoverished.
Kiwi fruit will tolerate about -15°C (5°F) in winter but the young shoots and are likely to be damaged by even fairly light spring frosts, so a sheltered position is essential in all except the very mildest areas. The branches are also rather brittle, an additional reason for providing shelter from winds. A position against a south or south-west facing wall is ideal and, although Kiwi fruit can be grown in the open against wires, this method can only be relied on in warm and sunny climates.
Kiwi fruit can, of course, be grown inbut they are so vigorous that you really do need a large greenhouse to do this successfully, and you would have to accept that there would be very little room for anything else. My view is that, if your climate isn’t mild enough to grow them outdoors, they can be more trouble than they are worth.
I prefer to plant in the early autumn, when the plants should have a chance to establish properly before the winter, or, better still, in mid-spring, when the worst of the cold weather has passed. Actinidia are almost always sold in containers, not bare-rooted and should be planted up to the soil mark on the stem, in a planting position prepared with organic matter and a dressing of bone meal. Firm them in well and slope the soil away from the plant, finally topping up with a mulch of compost.
Kiwi fruits are very vigorous plants.
Almost all the varieties are also uni-sexual and so must have a partner for pollination. Even in a limited space, therefore, you will generally need two plants and they are sometimes sold with a male and female in the same pot. They should then be planted as one, in the same planting hole, the shoots subsequently being trained in opposite directions. Sometimes, it may be possible to buy female plants on to which a male branch has been grafted. Where space allows you to grow more plants, allow one male for every five females and space them about 6m (20ft) apart. Where plants are grown against a wall, plant them about 20- 25cm (8-10in) away from the wall itself. Where they are grown with free-standing wires (see below), plant them in line with the support posts.
SUPPORTS AND TRAINING
Against a wall, use a system of horizontal wires, attached to vine eyes, screwed to wall plugs. You will need 10 gauge — 3.15 mm (1/8in) diameter — plastic-coated wire, and spaced 45cm (18in) apart to a height of 2m (6ft). In mild areas and given the room, a free-standing system of wires may be used. Erect supports similar to those used for the Worcester system of growing raspberries with two vertical, braced posts about 6m (20ft) apart and with top cross pieces 1m (3ft) across. Fix three, not two wires, one in the centre, in line with the centre posts and one, as with raspberries, at the end of each cross-piece.
Against a wall
After planting, cut back the main stem to just above the lowest wire and tie it to the wire. As new shoots arise, tie one vertically and two laterally along the wires, and cut out any others. As the main centre shoot grows upwards, tie it to the next wire and repeat thewith two more shoots. Repeat the process until the top wire is reached. When the lateral shoots are about 1m (3ft) long, pinch out their tips. This will encourage side-shoots to form and these in turn should be pinched out just above five leaves from the base. By the third year, some of these side-shoots will bear fruit and so become fruiting spurs. These should be pinched out at five leaves beyond the fruit cluster. Those that don’t should be pinched out five leaves above the base. In the winter, all of the side shoots should be cut back; either to two buds from the base, if they didn’t fruit, or to two buds beyond where the fruit developed, if they did. The process is then repeated in subsequent years.
On free-standing wires
After planting, cut back the main stem to a height of about 60cm (24in) and insert a firm cane or stake next to each plant. Tie the stem to the support and, as new shoots develop, select the strongest and train it up the cane, cutting out all others. When the main stem reaches the wire, pinch it out. Again more shoots will arise; select the two strongest and train them along the centre wire. Pinch out all other shoots. Side-shoots will arise from the two and should be tied laterally across the wires in pairs at intervals of about 45cm (18in), any others being cut out. Pinch out the tips of the side-shoots. Continue with this process until the wire framework is covered. Fruiting spurs will develop and hang downwards from the side-shoots and these should be treated in the same way as on wall-trained plants. In bothsystems, wayward shoots that arise elsewhere on the plants should be cut out promptly.
In early spring, give the plants 34g per square metre (1oz per square yard) of Growmore or, blood and bone; follow this with a mulch of well rotted compost. Ensure that the soil does not dry out in the spring and early summer but be careful not to overwater in the final stages of fruit swelling. This is different from the watering of most other fruits but it is important to ensure that the ripening process takes place slowly.
Fruit set will be improved if you assist with pollination by using a very soft brush to remove the pollen from the male flowers and dust it into the females. One male flower should produce sufficient pollen for about five females.
The mulch around the plants should control most annual weeds but perennial weeds can be hoed. The root system is not very shallow and hoeing is unlikely to damage it.
YIELDS AND NUMBERS OF PLANTS NEEDED
The number of plants is likely to be dictated by space but an established wall-trained plant on a wall about 2m (6ft) high and about 3m (10ft) wide should produce about 50-100 fruits.
HARVESTING AND STORING
It’s easy to tell when the fruits are ripe because they are slightly soft when pressed and snap very easily from the stalk. As I’ve already mentioned, they store well, keeping for about two weeks at room temperature and for about three months in a refrigerator. Harvest all fruit, ripe and unripe, before the first frosts and then ripen them gradually in warmth indoors.
The only problems likely to arise are red spider mites, aphids or caterpillars and these are seldom serious.