Detailed Explanation of Key Points in Summer Black Grape Cultivation Techniques

Black Summer is generally what we commonly call Black Summer grape, also known as Summer Black seedless, an American-European hybrid variety, currently cultivated in Hunan, Gansu, Qingdao and other places.

1. Trellis selection

Different places choose different trellis systems. The north mostly uses hedge trellises, while the south mostly uses single-trunk V-shaped or trellis systems. Summer Black grape can be grown on any trellis system. For hedge trellis cultivation with natural fan-shaped pruning, row spacing is 1.7m, plant spacing is 0.8m, and 500 plants are planted per 667 sq m. In areas requiring soil burial for cold protection, row spacing can be 2m, plant spacing 0.8m, and 420 plants are planted per 667 sq m. In places with abundant rain, the distance between the first wire above ground and the ground should be more than 80cm, to prevent rain from splashing mud and sand onto the fruit surface. This trellis system is conducive to fully utilizing land, wind, and light, and is especially beneficial for early high yield. Under general management levels, the yield per 667 sq m in the second year can reach more than 2000kg.

2. Cluster trimming and fruit thinning

Summer Black grape clusters are neat, mostly without shouldered branches, with occasional double clusters. It is recommended that for any double clusters, one be removed. For overly long clusters, pinch off 1/5-1/4 of the cluster tip 10 days before flowering. On average, only 1 cluster is retained per fruiting shoot. In actual practice, follow the principle of “strong shoots keep two, medium shoots keep one, weak shoots keep none”: that is, vigorous shoots at the upper end (front end) of the trellis may retain 2 clusters as appropriate, medium-vigor new shoots retain 1 cluster, and weak shoots and training shoots retain no clusters. A total of about 4000 clusters are retained per 667 sq m. Summer Black berries are tightly packed, so fruit thinning is recommended. Manual fruit thinning takes too much time; one may apply a small amount of water during full bloom and fruit set, or combine it with spraying fungicides, deliberately spraying the clusters to promote moderate flower and fruit drop. Alternatively, during full bloom and fruit set, moderately shaking or striking the vine can also serve to thin flowers and fruits.

3. Berry enlargement treatment

Currently in the domestic grape market, large-berried grapes are still favored. Fruit enlargement is beneficial for increasing yield and improving commercial value. Summer Black grape grows naturally with small berries, which is a common trait of seedless grapes, so enlargement treatment is recommended. That is, 15 days after flower drop, use 45-50mg/kg gibberellin solution to dip or spray the clusters, and repeat once after 12-15 days. Alternatively, when berries are the size of soybean grains, use 45mg/kg gibberellin solution, with every 1-1.5kg mixed with 10ml of forchlorfenuron plus Gaoshou (a peduncle hardening inhibitor) to spray or dip the clusters, once only.

4. Fruit bagging

Grape bagging has many benefits: preventing diseases, preventing pests, preventing bird damage, preventing pollution, ensuring yield, and ensuring quality. The berries produced are not only attractive in appearance but also good in taste. It is recommended that whether for field production or greenhouse cultivation, full bagging should be achieved.

5. Water and fertilizer management

As with other grape varieties, it is recommended in Summer Black grape production to apply heavy organic fertilizer. When establishing the planting site, apply 5000kg of organic fertilizer per 667 sq m. Thereafter, every other year, expand outward along one side of the planting trench and apply organic fertilizer in a trench once, applying 4000-5000kg per 667 sq m. In spring, apply a quick-acting nitrogen fertilizer once to promote bud break and stimulate large clusters. Apply a high-nitrogen three-element fertilizer once as an enlargement fertilizer. Apply a potassium fertilizer once before fruit ripening. The fertilizer amount cannot be generalized; it should be determined according to soil fertility, yield, and tree vigor.

6. Scientific winter pruning

Winter pruning is very important, directly related to the grape yield of the following year. Summer Black grape has good flower bud differentiation, high bud break rate, and high fruiting shoot rate. Therefore, for general tree vigor, short-spur pruning is mainly used, and vigorous shoots can be pruned to medium spurs. For mature vineyards with hedge trellis cultivation and natural fan-shaped pruning, it is recommended to retain 1500-1800 fruiting units per 667 sq m.