Reasons for pruning vines

It is important to note that winter pruning is the second most costly manual intervention in the vineyard. So why do we prune?

To organise the plant on the trellis

Pruning enables the vine to be well-organised on the trellis so that:

  • The plant can capture the maximum amount of light (particularly important in cooler climates)
  • Leaf bunching is avoided, thus reducing disease risk and increasing yield and quality
  • Bunch ripening is better synchronised

An ideal canopy is homogenous along the row (15 shoots/metre) and has an average leaf thickness of 1-1.5mm.

To allow for the passage of machinery and manpower

Winter pruning organises the plant along the trellis so that personnel and machines can pass along the alleys without causing damage and mechanical operations such as spraying and harvesting are more efficient and effective.

To produce a balance between the crop and leaf area

Unpruned vines produce:

  • Many short shoots further and further away from the trunk
  • Many small bunches of high acid low sugar berries
  • Irregular yields

In order to get quality fruit, there must be an appropriate balance between the level of crop and the leaf area on each shoot. The number of flowers on the vine shoot is determined in the previous year according to conditions at floral initiation. The size of each shoot (and therefore its leaf area) is determined at pruning, as the more buds are left on, the weaker their individual vigour. This is because more shoots have to share the limited amount of winter reserves and the capacity of the plant’s root system.

A heavy crop on short shoots will lead to over-cropping, which produces high yields of low quality fruit and weakens the vine the following year.

Shoots that have a disproportionally low crop will be over-vigorous, and may carry on growing past veraison, to the detriment of the quality of the fruit. Furthermore, they will have many large leaves and laterals, which will cause canopy shading.