What do you have to pay attention to when growing grapes?
Climate characteristics result from the sequence and interaction of various natural factors such as temperature, solar radiation, precipitation, humidity and wind. With regard to the soil, the nutrient content and water supply are particularly important, and these are largely determined by the geological composition.
The number of grape varieties worldwide is estimated at around 17,000, but it is probably even higher. Not all of these varieties are suitable as wine grapes for wine production; many are purely table grapes. Only grapes of the noble vine (botanical name: Vitis vinifera vinifera) are suitable for viticulture. This vine is descended from the wild vine (botanical name: Vitis vinifera sylvestris) and is one of the oldest cultivated plants ofmankind.
The different varieties of the noble vine have developed through mutations and/or crossbreeding. The grape varieties used in viticulture today are the result of centuries of breeding. In this process, the vines are evaluated according to certain criteria and only those plants are further propagated whose characteristics meet the desired requirements. This procedure is called selection breeding. In cross-breeding, the characteristics of different varieties are combined through plant crossing, so that a new grape variety(new variety) is created. Examples of such new varieties in Germany are Müller-Thurgau, Scheurebe and Huxelrebe. New varieties that are genetically more resistant to fungal diseases (i.e. PIWIs ) are called PIWIs, for example Regent, Solaris, Roesler, Johanniter, Rathay, Muscaris or Cabernet Blanc.
In order to achieve high qualities in cultivation, the characteristics of the grape variety must match the climate and soil conditions in the vineyard. In addition, the winegrower influences the quality through numerous viticultural measures:
- Planting density
It is important how many vines there are per hectare in the vineyard. The more densely the vines are planted, the fewer grapes they have to bear each and the deeper they have to dig their roots into the soil to supply themselves with sufficient water and nutrients. This makes them less sensitive to the weather.
During winter dormancy (on frost-free days in January and February), the shoots of the vine are pruned back so that only a few buds (eyes) remain. This reduces the number of grapes per vine, which increases the extract of the individual berries and thus improves the wine quality.
- Vine training
The fruit shoots of the vine(canes) are bent in a certain way and often attached to stakes or wires to control the growth of the plant. This ensures that the leaves of the vine receive as much sun as possible, so that the grapes can ripen optimally ( photosynthesis in the leaves is responsible for the formation of sugar in the berries) on the one hand, and are themselves protected from sunburn on the other. There are numerous forms of training, which can be divided into intensive and extensive systems as well as systems with a support framework; the latter depend on the distribution of the shoots (e.g. vertical, horizontal, free-hanging), the support (e.g. stake, wire frame, wooden framework), the distribution of the fruiting wood (trunk, cordon, head) or the planting density (spacing of the vines). Vine training systems vary from region to region.
- Foliage work
The purpose of foliage work is to make full use of photosynthesis in order to maximise the sugar in the berries and to keep the vine and the grapes healthy. Basically, it involves cutting off part of the vine's leaves at certain times during the growing season. However, it is important not to remove too many leaves in order to protect the vine and the young grapes from sunburn. Defoliation is usually done in autumn at ripening time, when the grapes are more robust, to improve aeration: The grapes then dry out more quickly, which reduces the risk of fungal diseases.
- Grape thinning
In order to further reduce the yield and thus improve the wine quality, part of the grapes is often cut off (thinned out) in the summer, before the grapes begin to ripen. This increases the extract of the remaining grapes.
Vineyards are monocultures that severely deplete the soil. Therefore, nutrients must be added to the soil from the outside. This is done with the help of organic or inorganic (mineral) fertilisers.
In regions with little rainfall or in particularly hot years, the soil must also be supplied with water from outside. There are several irrigation techniques for this (e.g. drip irrigation). In Germany, irrigation options for quality wine are strictly regulated.
- Plant protection
Plant protection means all measures that prevent the vine or the grapes from being attacked by diseases or pests. Even soil care serves as plant protection, but a variety of targeted measures are available to combat diseases and insects and animals or to prevent corresponding damage. These range from walls, fences and nets as protection against birds and wild animals to biological plant protection products, pheromone traps and beneficial insects to chemical (synthetic) pesticides used, for example, against weeds (herbicides), fungi (fungicides), bacteria(bactericides) and/or insects(insecticides). In organic viticulture in particular, great importance is attached to strengthening the vine and its defences against diseases; these measures also serve plant protection and are intended to prevent the use of pesticides as far as possible.