Grapevine Pruning

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.

Cane Pruning: The selection of 1-4 fruiting canes that have matured from last year’s shoots. The selected canes are typically tied down onto a fruiting wire as either a flat cane or arch. Renewal spurs are left to aide cane selection for the following year. In English vineyards single Guyot (unilateral cane) and double Guyot (bilateral canes) are the most popular choice of cane pruned training system.

Spur Pruning: Growth points are established along a permanent arm or cordon and consist of a 2 or 3 bud spur which will provide the fruiting shoots for that year. Spur pruning is often used in tandem with mechanical pre-pruners to remove large volumes of pruning wood, keeping pulling out costs down. However, spur pruning does impact bud fertility, therefore is best used with varieties that have a high basal bud fertility.

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.

Pruning Wounds

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

Mechanisation

With vines that are spur pruned, many vineyards around the world use pre-pruners to remove two thirds of the pruning wood, allowing for a pruner to quickly pass through making the final cuts. In 2017 when working for Chapel Down a colleague suggested we used a pre-pruner on our cane pruned vines, to remove the top 30cm of growth to speed up pulling out. We trialed a machine from Lamberhurst Engineering which made pulling out a lot easier, therefore quicker. We bought the machine and ran it across 250 acres of vines and in one season it had paid for itself. Pre-pruning has become popular in the UK, with growers either purchasing their own machines or employing a contractor, although it’s worth noting the trellis needs to be setup correctly to get the best results.

Pulling out machines are also being used around the world as labour becomes harder to source and more expensive. There are a couple of machines I know of in the UK, however having trialed one it is clear the vineyard trellis needs to be appropriate for the machine and should either be adapted or installed for the machine you intend to use.

Summary

Agro-Pro offers field training and crop management assessments to help vineyards make the right pruning decisions that promotes grapevine longevity by balancing vigour against target yields and quality parameters needed for the desired wine style. Agro-Pro is a member of The Simonit & Sirch Vine Pruning Academy. If you are interested in becoming a vine master pruner and want to be part of the Simonit & Sirch pruning community click here or contact us for more information and introductory offers.