Kiwi

Light and exposure

Kiwi wants sun, at least six hours a day, to flower well and carry its fruit through to harvest late in the season. A shaded spot gives you a leafy vine that is stingy with fruit. Pick the best-exposed wall or pergola in the garden, ideally facing the equator, sheltered from prevailing winds that damage young shoots and snap fruit-laden branches in late summer.

Shelter from wind matters almost as much as sun. A corner between two walls or along a windbreak hedge cuts down on breakage and speeds up fruiting. Put up a permanent support right at planting time, sturdy posts with tensioned wires or a solid timber pergola, because a mature vine is heavy and moving an established plant later is extremely difficult.

Watering

Kiwi drinks a lot, especially in summer once the foliage is thick and the fruit is swelling. A mature plant in open ground needs generous, regular watering right through the warm season, from fruit swelling to harvest, particularly in dry years, otherwise the fruit stays small or drops before it ripens. A thick mulch at the base holds moisture and saves you weeding around the shallow roots.

On the other hand, kiwi hates standing water. Soil that stays waterlogged after rain rots the roots within weeks, especially in heavy clay ground. Good drainage at planting time, working gravel or coarse compost into the soil, avoids this recurring problem.

Soil and repotting

Kiwi likes rich, deep, moisture-retentive soil, improved with compost or well-rotted manure at planting. A yearly top dressing of organic matter each spring keeps that richness up without needing to dig deep near the roots, which are shallow and dislike being compacted.

Crucially, kiwi prefers soil on the acid to neutral side and copes very poorly with active limestone. On chalky ground it develops a telltale iron chlorosis, leaves yellowing between veins that stay green, and the plant simply stalls. On a distinctly limy soil, you are better off planting in a large container or correcting the soil thoroughly before you start.

Temperature and humidity

Kiwi copes well with winter cold once established: a well-settled plant shrugs off -12 to -15 °C while dormant, which places it in USDA zones 7 to 9. It flowers late, several weeks after the stone fruits, which usually spares it the late frosts that ravage earlier species such as apricots.

Two moments stay risky. The young plant, for its first two or three years, is frost-tender and deserves a winter fleece or a thick mulch at the base through its early winters; the young shoots themselves are killed at -2 °C, even on a mature vine. And late in the season, an early frost can catch fruit still on the vine and spoil it, which is why it pays to pick before the first cold snap rather than wait for perfect ripeness outdoors. It also needs a long frost-free season, at least 225 days, to bring the fruit to maturity.

Pruning and upkeep

Pruning kiwi happens in two stages. In winter, outside frosty spells, you build and maintain the framework: choose the main arms that run along the support and remove dead wood, crossing branches and weak shoots. Never prune too late in winter, sap rises hard in kiwi and a late cut bleeds heavily.

In summer, green pruning finishes the job: shorten the long shoots of the year that shoot off in every direction and drain the plant for no benefit, leaving a few leaves past the last fruit set. This summer prune opens up the vine, lets light reach the fruit and makes the autumn harvest much easier.

Pests and diseases

The most serious concern with kiwi is PSA, a bacterial disease (Pseudomonas syringae pv. actinidiae) that has hit commercial orchards hard in recent years. It shows up as angular brown spots on the leaves, a reddish ooze on the trunk and branches, and can kill an entire vine in severe cases. In the garden, always disinfect secateurs between plants and avoid pruning in wet weather, the bacteria enters through fresh wounds.

More common and less serious, powdery mildew can appear on the foliage in muggy weather, and slugs happily go after tender young shoots in spring. Poorly drained soil also encourages root rot, one more reason to get drainage right at planting time.

Propagation

Cuttings are the most accessible method for a home gardener. Take semi-ripe cuttings ten to fifteen centimetres long from the current year’s wood in summer, strip the lower leaves and root them under a cold frame or in a pot kept humid under cover. Success rates are uneven but rewarding with patience.

Sowing, by contrast, is best avoided if you want reliable fruit: kiwi seed does not come true to the parent variety and, more importantly, does not reveal the seedling’s sex until it flowers several years later, a real problem since male and female vines look identical until then. To be sure of the right combination of sexes and a variety that fruits well, buy grafted or rooted plants clearly labelled by a nursery.

Month-by-month care calendar

Green Hub tips

• If you are only planting one kiwi, choose a self-fertile variety such as Jenny or Solissimo. With a classic kiwi you need both a male and a female plant, only the female bears fruit.
• Put up the permanent support right at planting time, sturdy posts with tensioned wires or a solid pergola. A mature vine is heavy and almost impossible to move once it has filled out.
• Be patient, the first fruit often only comes after three to four years, sometimes more. That is normal, the vine builds its framework before it starts fruiting.
• Harvest before the first autumn frost, even if the fruit still feels firm. It ripens very well at room temperature indoors, just like shop-bought kiwifruit.