Key Points of Winter Pruning Techniques for Grapes in Northern Regions

Winter Pruning Techniques for Grapes in Northern Regions

In soil-covered cold-protection areas, winter pruning of grapes is carried out before the vines are taken down from the trellis for cold protection. Depending on the growth vigor of the canes, the degree of pruning varies. Based on the length of the retained canes, there are very long cane pruning, long cane pruning, medium cane pruning, short cane pruning, very short cane pruning, and combined long-medium-short cane pruning methods. In very long cane pruning, generally more than 12 buds are retained per cane; in long cane pruning, 8 to 11 buds are retained; in medium cane pruning, 5 to 7 buds are retained; in short cane pruning, two or three buds are retained; in very short cane pruning, only the basal buds are retained.

The pruning method used in production must be suited to the environmental conditions, trellis type, training form, and the growth vigor of the variety. In arid regions, grapevines generally grow smaller, so planting spacing should be appropriately reduced and small trellises should be used. In areas with ample water, grapevines generally grow more vigorously, so with "single dragon" training, row and plant spacing should be appropriately increased and large trellises should be used. To suit the trellis type, corresponding pruning techniques must be adopted. Very short cane and short cane pruning should be the main methods; for pergola and vertical trellis fan training, combined long-medium-short cane pruning is generally preferable; for large pergola multi-main-cane training, long cane and medium cane pruning are mainly used; for vertical trellis single-arm and double-arm horizontal training, medium cane pruning is mostly used; for vertical trellis four-arm horizontal training, medium and short cane pruning are mostly used.

1 Long cane pruning

Canes under long cane pruning retain more buds, usually 20% to 30% more than under short cane pruning. However, canes under long cane pruning generally have a lower rate of bud break and shoot growth, with the number of sprouting buds accounting for only about 60% of the total buds; canes under short cane pruning have a higher rate of bud break and shoot growth, generally 80% to 90%. Although the bud break and shoot growth rate of long cane pruning is lower than that of short cane pruning, the actual number of new canes produced per unit of trellis surface is relatively greater. Therefore, as long as methods are adapted to local conditions and applied properly, and suited to the trellis type, either long cane pruning or short cane pruning can achieve high and stable yields.

2 Short cane pruning

In grapevines using short cane pruning, the fruiting position is relatively fixed. The fruiting unit has only 1 fruiting mother cane, with no renewal spur retained; after sprouting and fruiting, 1 new shoot is still retained as the fruiting mother cane, and pruning is done this way every year, also called single-cane renewal. When the fruiting position rises, a basal shoot is then selected as the fruiting mother cane to replace the original fruiting mother cane.

3 Medium and short cane pruning

In medium and short cane pruning, the fruiting unit may have no renewal spur retained, that is, single-cane renewal, or it may retain a renewal spur, that is, two-cane renewal. After sprouting in spring, 2 new canes are retained on 1 fruiting mother cane; during winter pruning, the upper one is given medium cane pruning and the lower one is given short cane pruning as a renewal spur. The following year, 2 new canes are again grown on the renewal spur, and the pruning method is the same as the previous year, forming a new fruiting unit. Pruning is done this way every year; when the fruiting position rises, canes arising from basal shoots are selected for renewal [Jishan Huayao].

4 "Single dragon" training

For grapes trained with the "single dragon" system, at pruning time each year, a cane with 15 to 20 buds is retained at the top of each main cane as an extension cane, and the lateral fruiting mother canes on the main cane are pruned with short cane pruning every year, retaining only one or two basal buds, so that the fruiting position is relatively fixed. However, after many years, a large "knob"-shaped cluster of fruiting mother canes will form, commonly known as a "dragon claw."

Under good fertilizer and water conditions and with relatively strong vine growth, alternating medium and short cane pruning can also be used, generally mainly short cane pruning, while medium cane pruning is applied to some robustly growing canes to increase the fruiting positions on the trellis surface and raise yield. Mother canes given medium cane pruning are then switched to short cane pruning after fruiting the following year, to prevent the fruiting position from shifting upward and to keep the vine vigorous. In vines pruned by this method, usually 1 robustly growing new cane is selected and retained on part of the "dragon claw" and given medium cane pruning, retaining five or six buds to let it bear fruit; such a cane is commonly called a "guai zi cane." Weaker short canes are given very short cane pruning, retaining one or two basal buds to induce sprouting canes that will serve as "guai zi canes" for fruiting the next year. After the "guai zi cane" fruits in the current year, it is cut off at the base in winter. This pruning method can increase the fruiting area, but too many "guai zi canes" must not be retained, otherwise the normal growth of new canes on the "dragon claw" will be affected, winter buds will differentiate poorly, and they often fail to sprout the following year, instead reducing the fruiting positions.

5 Combined long-medium-short cane pruning

Combined long-medium-short cane pruning has no fixed fruiting position and is suitable for pergola and vertical trellises. The degree of pruning depends on the growth condition of the canes. For the extension canes at the top of the main cane and side canes, pergolas generally retain 15 to 20 buds, and vertical trellises retain 12 to 15 buds, to maintain their growth advantage. The length of cane retention depends on the growth vigor and the spacing of the positions where they grow. Strong canes with a diameter above 1.0 cm can be given long cane pruning, with the number of retained buds not exceeding 12; medium canes with a diameter of 0.7 to 1.0 cm are given medium cane pruning, retaining eight or nine buds; canes with a diameter above 0.6 cm are given short cane pruning, retaining three or four buds; weak canes with a diameter below 0.6 cm are cut off at the base. Each side cane should maintain a certain spacing, and the size of the spacing is still based on the principle that the tip of the lower cane does not exceed the base of the cane in front, so that the canes are evenly distributed on the trellis surface. Canes growing well within the spacing range may be cut back to one or two buds as renewal canes for replacement. However, too many renewal canes should not be retained, so as to avoid crowding the trellis surface with canes, affecting ventilation and light penetration, weakening the vine, and causing reduced yield.

6 Very long cane pruning

Under conditions of ample fertilizer and water, some large pergola grapes are also pruned with very long cane pruning. Generally, on a certain part of the main cane or side cane, one or two robustly growing new canes are selected and retained as the fruiting mother canes for the following year, with the new canes retaining more than 12 buds. Those that grow too weakly and ripen poorly are cut off at the base. Whether main cane or side cane, attention should be paid to maintaining vigorous growth of the top extension cane, so that its growth vigor is stronger than that of the middle and lower side canes. Each side cane should maintain a certain spacing, generally the tip of the lower side cane preferably connects with the base of the side cane above, that is, there are more than 12 buds between the upper and lower canes, and side canes sprouting within this spacing are cut off at the base. This pruning method is suitable for varieties with relatively strong growth vigor. At the same time, because the canes are arranged relatively evenly on the trellis surface, the trellis surface can be fully utilized and the yield is relatively high. However, if fertilizer and water are insufficient and a strong vine cannot be maintained, a large number of "blind eyes" are likely to appear, the fruiting positions are greatly reduced, and yield declines. Therefore, under general conditions this method should not be used.