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When to cut wine?
Strictly speaking, of course, it is not the wine that is pruned, but the vine, i.e. the vine. Pruning is an important factor for the yield of the vine and thus later for the quality of the wine. Without pruning, the vine would grow uncontrollably and form new lateral "stocks" with shoots and buds every year. This expansion in area would lead to high yields and lower wine quality.
Pruning therefore regulates the number of buds on the vine from which new shoots can form. By limiting the number of new shoots, one also reduces the number of grapes and thus increases the wine quality: the fewer grapes a vine bears, the more extract each individual berry contains and the more substance the wine later has. The effect of pruning on the quantity and quality of the grapes depends on the grape variety, the training system and the location, age, health and growth behaviour of the vine. The sprouting and growth behaviour of the vine is in turn influenced by the arrangement of the shoots.
The so-called one-year-old wood, i.e. the shoots of the previous year, is always pruned. In addition to leaves, tendrils and shoots (the later grapes), each shoot also forms new buds. These buds already carry all the plants for new shoots, but are initially enclosed by bracts and filled with fine woolly hairs in the cavities. This allows the bud to overwinter protected from the cold (which is why it is called winter eye) and then sprouts the following year.
Pruning takes place during the Winter dormancy of the vine, i.e. between leaf fall in autumn and bud break in spring; in the northern hemisphere this phase is between December and March. In so-called winter pruning, by far the largest part (80 to 90 percent) of the one-year-old wood is usually cut away completely in January and February , leaving an average of two one-year-old shoots per vine. For frost-prone In the case of grape varieties and in such locations, as well as in the case of young vineyards, pruning is often delayed until March.
The one-year-old shoots that remain are then pruned again so that just enough eyes remain for the shoots that develop from them to reach an optimal strength and length and to ensure the physiological balance of the vine. A short shoot is called a cone and bears 1 to 4 eyes. A medium-length shoot is called an extender and bears 5 to 7 eyes. A long shoot is called a cane or Arch and bears 8 to 12, sometimes even 15 eyes.
Only healthy and mature vine wood with a length of 110 to 140 cm is cut. If the vine grows evenly, leave as many eyes as sprouted the previous year. If growth is weak, fewer shoots are cut off and the remaining shoots are cut shorter (with fewer eyes). In the case of strong growth, more shoots are cut off and the remaining ones are cut longer (with more eyes). The average number of eyes per square metre of vine stand area (row distance x vine distance) is between 4 and 8.
The one-year-old shoots are cut at an angle away from the eye 1 cm above the last node that is to remain. This is best done with a pruning shear or Pruning shears or loppers or a saw; pre-cutting machines can also be used for certain forms of cultivation. All cuts should be kept as small as possible, as they represent an injury to the plant. Immediately after pruning, therefore, all cut wounds should be coated with a wound treatment agent which, among other things, prevents fungal infestation.
Apart from the winter pruning described here, there are other occasions to prune the vines: On the one hand, it may be necessary to prune the vines unscheduled after hail or frost damage. Secondly, the so-called green harvest often takes place during the growing season: thinning as a special form of pruning in which grapes are cut away from the vine during the growth or ripening phase in order to increase the quality (extract) of those that remain.
Terminology:
- Foliage = leaves of the vine
- Tendrils = attachment organs of the vine
- Shoots = young shoots of the vine
- Eyes = buds of the vine, from each of which a shoot grows
- Shoots = inflorescences of the vine from which the grapes develop
- Nodes = nodes on the shoot from which leaves, tendrils, eyes and shoots develop
- Internodes = Shoot axes of the vine between the nodes