This first work of a new vintage is a decisive factor for the yield and quality of a wine. Without pruning, the vine would grow uncontrollably and build up new canes every year from the buds of each of last year's shoots, which would continue to spread out in tiers while the lower canes become woody. As the grapes are only ever formed on one-year-old wood, pruning ensures a balance (physiological equilibrium) between yield (generative growth) and growth (vegetative growth) without too much old, unproductive wood being formed. The choice of the appropriate method depends on the soil type (fertile-infertile), the vine training (single stake, wire frame, pergola), the climate (humid, dry), the grape variety (fertility, tendency to coulure), the rootstock and local conditions.
The picture on the left shows young and old wood before pruning in winter; the picture on the right shows pruning with a pruning knife.
Wood types and fruit formation
The grapevine bears its grapes exclusively on the green shoots of the respective year. These grow in spring from winter buds (eyes), which are located on the one-year-old wood and contain flower buds that were already laid the previous year. Annual pruning ensures that sufficient fertile wood is retained, that the fruiting area does not "migrate" outwards and that excessive formation of old, unproductive wood is avoided.
In practice, only one fruiting cane (B) and one cone (E) usually remain on the vine when pruning in winter. However, the vine forms many shoots in summer, which become woody by winter and are then considered annual wood. The diagram shows this schematically to illustrate that several fruit-bearing green shoots emerge from the eyes of the annual wood in spring. Without pruning, numerous one-year-old canes would therefore remain on the vine. This illustrates the natural growth of the vine without the annual winter pruning.
A = perennial (old) wood
The trunk and head form the permanent supporting structure of the vine and remain in place for several decades. Depending on vine training, the perennial support structure also includes perennial arms or cordons, on which the annually renewed fruiting wood is attached. The perennial or old wood (from the 3rd year onwards) of the grapevine primarily fulfils static and physiological functions and is permanently barren.
The reason for this is the vine's special growth strategy as a climbing plant, which is designed to penetrate quickly into light-rich areas by forming new, long shoots each year and to concentrate both growth and fruit formation there. The fruiting biology of the vine therefore requires the annual renewal of fruitful shoots, which explains and justifies the central importance of annual pruning.
Other fruiting plants such as apple, pear, cherry and plum trees, on the other hand, are not climbing plants but long-lived canopy trees whose strategy is based on permanent fruiting structures (short shoots).
B = biennial wood (fruiting cane, arch)
The horizontally attached fruiting cane (arch) is selected as fruit-bearing wood during annual pruning (see selection criteria below). Green shoots sprout from its eyes in spring, which bear the grapes in the same year. At the time of pruning, this is botanically still annual wood. In the following winter, this wood is biennial (therefore labelled as such in the diagram) and is then usually removed.
C = one-year-old wood (one-year-old canes)
Annual canes (woody shoots from the previous summer) that are newly formed in the course of a vegetation cycle. The eyes (buds) are located on their nodes, from which new green shoots emerge in spring. Most of these annual canes are removed during annual...
