Why do we need trellis systems in vineyards? Did you know that the type of trellis used can influence the wines taste?
Grapes grow naturally up towards the sun. In fact grapevines would be happy hanging around treetops, stealing available sunlight whilst producing grapes high up. Birds and other animals would enjoy the sweet fruit and spread the seeds, ensuring that grapevines continue into the future.
We, as wine-lovers, see that it’s not easy to pick grapes from treetops. So we control these far reaching vines in an attempt to optimise their quality and quantity, plus make it easier for us to pick.
The way to optimise the performance of a grapevine is to balance the amount of fruit development with the amount of leaves which are the energy-producing parts of the vine. Having too much fruit without having enough energy-producing leaves will result in an imbalance. An imbalance means the grapes cannot fully ripen and the vine is stressed by trying to provide all the grapes with sufficient energy.
We also configure our grape vines so that grapes are exposed to the sun and wind. We don’t want too many leaves creating a thick canopy that traps moisture. An open canopy helps grape ripening by sun exposure, drying of grapes and leaves quickly after rain.
Methoxypyrazine is a compound found in Sauvignon Blanc and Cabernet Sauvignon. It is responsible for the green bean, cut grass, leafy flavours often found in these wines. Shading of the grapes within the canopy can result in an increase in methoxypyrazine and subsequently an increase in these green flavours in the wine. Therefore the trellis system used can influence the flavour of the wine.
We need to retain the appropriate number of buds to optimise grape production and canopy leaf density as too many buds results in thick canopy that blocks the sun and wind, and promotes mildew and other diseases which can negatively affect grape ripening. A thick canopy also makes it more difficult to pick and to prune in spring. The general rule is 4-7 buds per linear 30cm of canopy when pruning to create a crop load and canopy that are in balance, and wines with more intense flavours and fewer unripe flavours.
Trellises are usually oriented North-South to allow sun exposure on the east side of the canopy in the morning, and on the west side of the canopy in the evening. There is usually about 3m between the canopy wires in adjacent rows.
There are several types of trellises, each with its own advantages and disadvantages. However effective and efficient use of trellises assists the winemaker produce wines of quality and value from vine to glass.