Summer pruning of grapevines is an essential follow-up to winter pruning, typically carried out from May to August when the plants are in their active growth phase. This process is usually done 4 to 5 times throughout the season. The main goal of summer pruning is to balance vegetative growth with fruit production, control apical dominance, reduce unnecessary energy consumption, improve air circulation and light penetration, and enhance fruit development and flower bud formation. Here are the key aspects of summer pruning:
At the time of bud break, shoots are selected and developed. In areas prone to late frost, this can be delayed by 15 to 20 days. Bud thinning involves removing dense branches, shoots on the trunk, main and side arms, as well as any non-productive shoots and basal shoots that may appear at the base. This helps minimize nutrient waste. Shoots are pruned when they reach a length of 10 to 20 cm, allowing for the visibility of inflorescences. For trellis systems, about 6 to 10 shoots per meter are left, while for framework systems, around 20 to 25 shoots per square meter are maintained.
When vines grow to about 30 to 40 cm, their tips are guided onto the trellis frame to prevent wind damage or breakage from fruit weight. As new shoots elongate, the growing vines should be tied 2 to 4 times, while fruit-bearing shoots need to be tied 1 to 2 times.
Tendrils that wrap around branches not only hinder plant growth but also consume valuable nutrients. These should be removed promptly to maintain plant health and efficiency.
Pinching the shoot tips, along with removing lateral shoots, can improve flowering and increase fruit set. The best time to top the vine is when the flower clusters begin to spread, leaving 10 to 12 leaves from the base upward—this means leaving 7 leaves above the upper cluster. For nutrient management, a topping of 10 leaves is recommended.
Lateral shoots, which are vines that produce additional shoots and vegetative buds, can compete for nutrients and lead to overcrowding. Except for empty spaces, all must be removed. However, the last top shoot should have at least one leaf left to avoid forcing dormant buds to sprout during winter. Secondary shoots should also be managed several times throughout the season.
For varieties like Rosette and Kyoho, where the spike length is proportional to the ear tip, it’s advisable to remove the first 1/4 to 1/5 of the tip 3 to 5 days before flowering. For long-spiked varieties, the entire spike may need to be removed. Additionally, due to excessive branching and fruiting, it's important to remove too many small flower clusters to focus the plant’s energy on developing larger, higher-quality fruits.
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