Training and Pruning for Kiwi Plants

Appropriate training and pruning are critical practices for kiwifruit (Actinidia deliciosa and other species). They help manage the plant's vigorous growth, optimize fruit production, and ensure/maintain good general plant structure, health, and longevity.

Training Systems for Kiwi Plants

T-Bar and Pergola Systems

Kiwi plants require support structures (trellis) to grow (climbing nature) and support heavy fruit loads. The two most widely used training systems are the T-bar and pergola systems. Below, we focus on them and present basic guidelines for performing each. The article ' Kiwi Planting ' contains extra information on how to create the trellis system for each.

T-Bar System: This is the most commonly used system, where a horizontal bar is placed atop a vertical post (a structure resembling the letter T is formed). The structure allows the kiwi vines to spread horizontally (forming a tunnel), allowing good air circulation and light penetration. This system is typically about 1.8 meters (6 ft) high, allowing easy access for pruning and harvesting.
Pergola System: Vines/shoots are trained over a horizontal overhead trellis, similar to grapevines. The overhead canopy also supports heavy yields, making it suitable for high-density planting. The pergola system often requires more labor and is a bit more expensive to establish than the T-bar system, but it can result in higher yields and more efficient use of space. At the same time, the fruits have higher homogeneity and better shape due to the more uniform sun exposure.

Training of Young Kiwi Plants

1st Year (Establishment Phase)

Depending on the propagation material used, planting can take place in early spring or early fall. Farmers' advice is to establish the trellis system first and then plant the kiwis. During the first year, the grower should select one main shoot (strong) as the main leader (future trunk), and a wire can be used to guide it vertically. Maintaining a single trunk will simplify future training and pruning efforts. No other pruning activities should be performed in the first year, allowing the plant to adapt and form a good root system. Regular watering and balanced fertilization are required in order to help the establishment of the plant.

2nd Year (Training the Canopy)

In the second year, the grower focuses on the development of lateral arms by pinching the main leader once it reaches the desired height. In the T-bar training, two strong lateral branches should be selected to grow from the top of the main shoot (trunk) in opposite directions and, if possible, at the same level (height). This structure will become the basis for fruiting wood in subsequent years. The lateral branches should be tied to the trellis, training them to grow horizontally. The kiwi grower should remove any shoots that emerge from the trunk to help the plant redirect its resources to the main frame. The weak, crossing, or downward-growing branches should be removed. Effective canopy management improves light penetration and reduces humidity around the fruit, decreasing the likelihood of fungal infections.

3rd Year (Preparing for Fruit Production)

In the third year, our activities focus on developing fruiting arms along the lateral branches. These arms should be spaced 30-60 cm (1-2 ft) apart, allowing enough space for the leaves to expand and the fruit to grow without overcrowding. Proper spacing allows for air circulation and light penetration, which is critical for fruit quality. The non-productive (or structural) shoots (waterspouts and suckers) can be cut back. After this year, the plants enter the reproductive phase, and the pruning activities will focus on maintaining the initial training scheme/frame, balancing vegetative and fruit growth, and removing the diseased or damaged shoots/branches.

Seasonal Pruning Principles and Best Practices

Winter Pruning (Dormant Pruning)

Seasonal winter pruning is crucial for managing the plant structure and encouraging fruit production. This pruning is typically done in late winter when the plant is dormant and before the sap starts flowing to reduce the stress and damage. Before starting, it is important to remember that the kiwi plants produce fruit on the current season's growth, which arises from one-year-old wood. Recognizing the difference between fruit buds (plump and rounded) and vegetative buds (slender and pointed) is important. The growers usually start by removing any dead, diseased, or damaged canes to prevent the spread and ensure healthy growth. Any canes that grow very densely (close to one another) should be thinned out to improve light penetration and air circulation and decrease the fruit damage due to friction. Finally, productive canes should be pruned back to 2-4 buds. This ensures vigorous growth in the spring and a better fruit set.

Pruning for Kiwi Plants

Summer Prunings

Some additional interventions (lighter prunings) might be needed in early summer to manage canopy size and improve fruit exposure. During this period, growers are removing suckers and waterspouts. Infected or infested shoots are removed to keep the crop healthy. In the case of very dense canopies, the excessive foliage should be removed to improve sunlight penetration and ameliorate fruit development and quality. However, foliage thinning should be performed cautiously in areas with high light irradiation and temperatures so that the fruit is not exposed to direct sunlight, risking sunburns. Finally, kiwi farmers could clear any areas where branches overlap to improve airflow and reduce the risk of fungal infections.

Fruit thinning may also be applied during this period. Some farmers may thin in the flowering stage to gain time and resources. However, this is not advised since the risk of infection from pseudomonas is quite high during blooming and can lead to further reduction of the viable flowers. At the same time, the cut could serve as an extra entry point for the bacteria. From the fruit set until maturation, growers pass through the field and remove underdeveloped and malformed (butterfly-shaped) fruits, so that the resources can be redirected to the remaining fruits that obtain larger sizes (higher marketable price).

Rejuvenation Pruning

Kiwi plants can remain sufficiently productive until the age of 35-40 years. After that time, many farmers chose to apply rejuvenation pruning to their plantations. Rejuvenation pruning is a technique used to restore the vigor and productivity of older kiwifruit vines that have become less productive over time. Typically performed during the dormant winter season, rejuvenation pruning involves removing a substantial portion of the old wood, focusing on cutting back canes to their base or to a few strong buds. After rejuvenation pruning, the vines may initially produce less fruit, but this sacrifice leads to stronger, healthier shoots that are more productive in the years to come. Proper care, including balanced fertilization and irrigation, is crucial to support the plant's recovery and maximize the benefits of this process.

Pruning for Kiwi Plants

Best Practices and Common Mistakes to Avoid when Pruning Kiwi Plants

Cleaning the pruning tools: Always use sharp and sterilized pruning shears to prevent the spread of disease and make clean cuts.
Adaptation to Climate Conditions: You must adjust pruning practices based on local climate conditions. In colder regions, you have to avoid late summer pruning to reduce frost damage risk. In areas with very warm summers and intense sunlight, you may have to offer the fruits enough shade to protect them from sunburn.
Frequent Monitoring: Farmers are advised to inspect their crops regularly throughout the year for signs/symptoms of pests or diseases and remove affected areas as soon as possible.
Time and Balance are of the essence: You are advised to avoid over-pruning your kiwi plants. This can stress them and reduce yields. You are advised to learn if the training system and variety selected have any specific needs. Always prune during the recommended time frames. Pruning too early or too late can affect the plant's growth and fruiting potential.

In conclusion, successful kiwi cultivation requires a well-planned training and pruning program and good execution. Establishing a strong plant structure in the first few years is essential for long-term productivity. By following best practices, seasonal pruning practices of fruit-bearing kiwi plants can enhance fruit quality and yield.