Grapevine pruning is undoubtedly the most important vineyard task of the year and is a vital part of training and establishment. There are two types of pruning, winter pruning when the vines are dormant and the previous year’s canes are removed and summer pruning which occurs mid-season and is the removal of green shoots. The purpose of both is to manage vine growth in accordance with our chosen management practices to achieve a desired yield of a certain quality. When grapevines have been sympathetically trained, through considerate pruning and management, only a few cuts are required with a skilled pruner assessing the vine and making the necessary cuts in seconds, however mismanaged vines are much harder to prune and require much more thought. It only requires one year of poor pruning to have a negative effect on vine growth and in some cases, it can take years to rectify.
How Grapevines Grow
Grapevines are heliophiles (attracted to light) but as they’re unable to support themselves they have developed a creeping nature that allows them to find structures they can use to support themselves. This allows the vines to sprawl, eventually dropping their grapes/seeds as far away as possible. Understanding the sprawling nature of the grapevine is vital to successfully managing grapevine growth, whilst preserving the health and longevity of the vine.
Types of Pruning
There are different pruning techniques adopted around the world, however most are a form of cane or spur pruning.
Pruning to Vigour
Assessing a grapevine’s vigour is essential when pruning. Retaining too many buds, will result in weak growth that will affect the vines ability to ripen. Leaving too few buds will lead to lower yields and overly strong growth that can affect the cane choices and yield for the following year. When assessing grapevine vigour it’s important to step back and get an overall view of how well the vine has grown, particularly looking at the number of shoots that have successfully grown from the buds that were left the previous year. Cane number, node number, internode length and cane thickness all play an important part in determining how best to balance vine vigour. Some vineyard managers will measure pruning weights against cropping weights and indexes to ascertain the bud number to leave, where others will simply complete a charge count, scoring shoots to acquire a total score that will relate to a bud number that should be left.
When grapevines are pruned, a wound is created, leaving the vine exposed to microorganism. Unlike most other trees, grapevines do not produce a healing callus, instead they create an area of dead wood (desiccation cone) at the wound site which dies back into the plant. The size of the desiccation cone is fully dependent on wood age and thickness. When making cuts on old wood, it is always recommended to leave some spare wood for dieback, this can then be cut back in the following year. With 1 or 2 year old wood the cut can be tighter leaving a crown bud which helps promote healing. Some vineyard managers like to use pruning wound treatments to try and seal the wounds to prevent microorganism infection, the effectiveness of which is debatable. Managing vine growth with respectful winter and summer pruning, cutting 1 and 2 year old wood will result in fewer wound areas therefore reducing infection surface area