The vine's main trunk and its thick arms supply the leaves and grapes with water and nutrients. Because vines draw and evaporate more water than other woody plants, the trunk has to work harder and therefore requires more maintenance. Especially water shoots and tendrils should be removed regularly; ties also need to be checked regularly and, if necessary, replaced.
Together with the roots, the trunk also serves as a "storage battery" for the vine. Here, the excess sugars produced on sunny days are stored as a sugar solution, which is transferred into the grapes during the ripening period in autumn, and stored for frost protection during winter-- another reason to look after your vine trunk carefully!
Every spring, water shoots develop from the main trunk, which can be left if the vine needs rejuvenating. Otherwise, they need to be removed in spring by shoot thinning before they start to become woody, or pruned off later to prevent the development of sap flow obstructions in the trunk.
Usually, grapevines in your garden are tied to an espalier, made of wires or wooden slats. Increasing girth growth combined with the wrong tying material can lead to constrictions. In the FassadenGrün Online Shop you can purchase suitable tying material, which will not strangle your vines. Old tendrils twined around the stems can also lead to distorted growth and constrictions; they should therefore be removed.