Pruning Kiwi Vines: Timing and Techniques

When it comes to kiwi, there are two primary varieties to consider: Actinidia arguta, known as the hardy kiwi, and Actinidia deliciosa, often referred to as the fuzzy kiwi. For successful pollination, it’s essential to have both male and female plants of the same species, as only the female produces fruit. While self-fertilizing varieties exist and yield smaller fruit, planting a male alongside a female will ensure a better harvest. The hardy kiwi can handle temperatures as low as -35°C (-25°F) and matures its fruit in late fall, whereas the fuzzy kiwi bears larger, brown, fuzzy fruits and can tolerate temperatures from -12.2°C to -9.4°C (10-15°F), with some cold damage at -17°C (0°F).

Optimal Growing Conditions

Establishing a robust root system in the early years is crucial for kiwi cultivation success. Three key factors come into play: warm roots, nutrient-rich soil, and adequate moisture. To create the perfect environment, choose a sunny site with well-draining soil that is rich in organic matter. Watch for signs of nitrogen deficiency, such as yellowing leaves, particularly in overly alkaline soils. Kiwi plants are sensitive to salt and prefer a sunny location, although they can tolerate some shade. Additionally, they benefit from protection against strong winds.

Watering Needs

During the growing season, kiwi vines require a substantial amount of water, yet they must be planted in well-drained soil. Consistent watering is vital, particularly in the heat of summer, as drought stress can cause symptoms like wilting leaves and browning edges. Continuous stress may even lead to defoliation, with new shoots appearing afterward.

Fertilization Guidelines

Kiwi plants are heavy feeders, particularly needing nitrogen during the first half of their growing season. While adding nitrogen later can increase fruit size, it is not advised as it leads to poor storage quality. In basic soils, consider applying a citrus and avocado fertilizer around early March and follow up with additional applications in early summer. Mulching with manures or straw can enhance growth as well. However, avoid placing mulch directly against the vine to prevent crown rot.

Planting Steps

1. Prepare the Site: Create a hole that adequately accommodates the roots without crowding. Mix slow-release materials such as rock phosphate, kelp meal, and compost into the soil before planting.
2. Planting Techniques: Handle potted plants carefully to avoid disturbing their roots. For root-bound plants, gently spread the roots to encourage growth. Make sure not to let the roots dry out. Plant kiwi vines at the same depth as they were in their nursery pots and soak the area post-planting to eliminate air pockets.
3. Spacing: Space vines about 3.5 meters (10 feet) apart or train them in opposite directions. Male and female plants can be up to 10.7 meters (35 feet) apart for effective pollination. To encourage bee activity for pollination, prune any competing flowers near the kiwi when they bloom.

During the first year, ensure regular and deep watering, especially during dry spells. Annual mulching will reduce weeds and retain moisture. If necessary, use insecticidal soap to manage pest issues. For optimal results, train kiwi vines to a sturdy trellis or fence system.

Flowering and Pollination

Kiwi plants are dioecious, meaning they produce male and female flowers on separate plants. To promote cross-pollination, intersperse male vines among female ones, as one male can effectively pollinate up to eight females. While male vines bloom profusely, they bear no fruit, characterized by numerous stamens but lacking styles. In contrast, female flowers showcase the opposite features. Pollination primarily occurs via honey bees; however, since the open clusters are not particularly appealing to them, a lack of bees can result in smaller, misshapen fruit.

It’s important to note that kiwi vines typically begin fruiting only after four years of growth. They produce fruit on the previous year’s wood, with a single plant yielding up to 100 kg of fruit.

Harvesting Techniques

For Actinidia arguta (the hardy kiwi), the fruit should drop or be easily removed when ripe, often picked at the mature-ripe stage and allowed to ripen off the vine. These fruits, generally green and fuzz-free, resemble grapes in size. Inside, they have the familiar appearance of regular kiwi with small black seeds and a vibrant green hue. Some varieties even exhibit red tones in the skin or flesh, and these hardy kiwis tend to be sweeter than their fuzzy counterparts.

Actinidia deliciosa (the fuzzy kiwi) should ideally be harvested no earlier than November 1, with November 15 being preferable. The seeds should be fully black by this time. After gathering, store the firm fruit in plastic bags within the refrigerator. When ready for consumption, remove them to the counter to ripen. These oval or oblong fruits can grow up to 6.6 cm (2.5 inches) long and have a russet-brown skin covered in fine, stiff hairs. Their flesh is bright green or occasionally yellow, with a succulent white center containing tiny, nearly unnoticeable dark seeds.

Routine Pruning Care

Begin by cutting the plant back to approximately 30 cm (1 foot) from the ground at planting. Select a vigorous shoot to develop rapidly to the top of the support, gently tying it to a sturdy post while removing less vigorous shoots. Once the vine reaches the top, tip it back and allow two buds to grow near the top, then train them along the support.

1. Prune to one or two buds upon planting.
2. Train one robust shoot as the trunk and remove all others during the first year.
3. Head back the trunk when shoot growth at the end loses vigor.
4. Continuously remove lateral shoots while allowing the trunk to grow beyond the wire, then head back just below it.

Plan a significant annual pruning session in early February, focusing on eliminating excess growth and shaping the main trunk. Cut back vines to three or four buds—never further, as kiwis flower on last year’s wood.

Further steps include: 5. Choose two shoots to create cordons: one going in each direction on the wire, trimming back to 1/4 inch diameter during dormancy (Year 1). 6. Year 2 shoot growth requires dormant season cuts.

Every two to three years, prune back lateral vines originating from the main trunk, ensuring to balance cuts on both sides. Male vines should be pruned immediately after flowering, cutting flowering arms to between 43.18 cm (17 inches) and 66 cm (26 inches) in length to preserve new green growth. To maintain proper structure and size, use secateurs for shaping, prevent tangling, and ensure light and air circulation throughout the plant.

Managing Pests and Diseases

Generally, kiwi plants are resilient against pests but may face some unique challenges. Notably, their trunks emit a catnip-like scent that attracts cats, which can rub against the plants, damaging new shoots in spring. Young plantings may also contend with pests like garden snails. Additionally, deer and gophers can pose threats to leaves and roots, respectively, while scale insects may build up in significant numbers. Lastly, root-rot nematodes can adversely affect plant vigor when present.

By taking these detailed steps and considering the specific needs of kiwi vines, gardeners can enjoy a fruitful harvest while caring for these vibrant plants effectively.