Left untamed, the grapevine is an unruly, perennial, deciduous, climbing plant. Using its tendrils, amongst other adaptive features, the vine, a liana, will use nearby trees to climb up and above the canopy established by competing trees and plants. A heliophyte, Vitis has by process of natural selection acquired a number of ingenious adaptations to support its upward struggle for sunlight. First, the vines shoot apex inhibits the growth of lateral or axillary buds so that the plant may grow vertically, a phenomenon known as apical dominance. Next is acrotony, whereby the top latent buds on a fruiting cane develop first, leading to the inhibition of the development of the bottom buds on the cane. Each of these adaptations promotes upward growth, contributing to the vine’s colonisation of nearby spaces in its hunt for sunlight. For several thousands of years cultivation of grapevines has been with the explicit goal of making wine. Though exceptions exist, this cultivation relies almost entirely on diligent pruning. For the most part, pruning methodology has depended on several primary factors, namely planting density, desired yield and fruit quality, and more recently mechanisation. Alongside the growing rejection of industrial agriculture, a renewed approach to pruning has grown popular, one centred around respecting vine physiology and maximising health and longevity. Known colloquially as sap-flow pruning, this method respects the physiology of the vine, pursuing balanced yields and improved longevity. I discussed this approach with respect to Nebbiolo with Tom Myers and Philine Dienger.

A brief history of fruit and cultivation

Plants have evolved to produce fruit, an adaptation essential to their survival. Fruit supports the distribution of progeny while protecting developing seeds from adverse environments as well as foraging animals. Additionally, when ripe, seed-bearing fruit attracts animals who subsequently eat the seeds, which are then spread as waste is excreted. Fruit has also provided sustenance to humans for many millions of years, with evidence of cultivation of figs 11,500 years ago. As early c. 6000 BC, humans were cultivating vines, harvesting grapes for the explicit purpose of making wine. Ancient Egyptians and Phoenicians discovered that different training techniques could promote more abundant and fruitful yields. In the 1st century AD, writers such as Columella and Pliny the Elder gave advice to vineyard owners about what type of vine trainings worked well for certain vineyards.

The widespread study and utilisation of training systems began in the 1960s with vine growers in California, Washington, Australia and New Zealand. For much of the last 60 years pruning methods have largely been determined by cultural and labour constraints, mesoclimate, and desired style. Pruning with an eye to improving vine health and longevity, balancing yields and vigour, increase alimentation and subsequently vine resilience is a fairly recent development. Emerging alongside a growing concern with industrial agriculture and coupled with the reinvigoration of ‘old ways of working’, sap-flow pruning, which seeks to better consider what we know about vine physiology within the pruning method itself, has become the tool of choice for many great estates.

Beyond a single season

Throughout the depths of winter, the vine is dormant, surviving on carbohydrate reserves stored (mostly in the roots and older wood structures) during the previous growing season. Dormancy can be further divided into two distinct phases: endodormancy and ecodormancy. It is in winter, during endodormancy and before ecodormancy, that the most formative pruning tasks take place. Winter pruning requires vineyard workers to remove the majority of the previous year’s growth, simultaneously selecting the fruiting wood as well as mapping the year’s canopy structure. Perhaps the most crucial shift to be had in one’s attitude to pruning is in the transition from seeing pruning as a task necessary to cultivate fruit in a single season to an ongoing activity existing as a part of an ongoing cycle, one which can shape the vine throughout the entirety of its life.

‘It’s best not to look at pruning as being isolated to that season, instead, it forms part of an ongoing cycle, the decisions you make each winter impact the vine the following year, the year after that and so on and as such directly impacting vine health and longevity’ Tom explains. The same can be said about the selection of the fruiting cane and the position of the renewal spur during winter, the decision made at this point each year potentially determines the shape of the structure for the duration of its life, sculpting its development with respect to its organic growth is perhaps the first step in pruning for longevity and vitality.

Traditional pruning systems, less constrained by space and mechanisation, regularly grew among three dimensions, freely forming numerous cordons. Naturally, this freedom meant less need for cuts. Modern pruning, guyot in the case of Nebbiolo, requires the vine to adhere to strict geometry, maintaining a particular point of vegetation (below and in line with the fruiting wire) and fruiting. Where this vegetative point shifts, very quickly (often in only three years), the vine grows out of its geometric system, resulting in the need for large and frequent cuts, even where the vine itself is healthy. And thus the winegrower is presented with a challenge. A key principle of sap-flow pruning is that the pruner, sculpting throughout the vines life, directs the grapevine’s trunk formation according to its desire to spawn new wood, maintaining a vegetative point without the need for damaging cuts.

In order to avoid this shift in vegetative point over time, not only should pruning be seen as a perpetual activity, but also the grapevines organic growth patterns should be amalgamated within the guyot system. The vine should be allowed to grow wood, each year a little more, in perfect conditions only 1-2 cm of wood each year, this should be guided by the positioning and selection of the spurs, subsequently determining which buds grow. Considering the vine requires roughly 5 sugar molecules to produce one tannin, part of both Tom and Philine’s philosophy in their own vineyards consists of minimising the extent to which the vine expends unnecessary resource via the growth of ‘unnecessary’ wood.

Continuation of a perennial structure

Understanding how and why the vine grows is of the utmost importance in ensuring it is pruned according to the instructions of both its variety and its shared organic adaptations. Nebbiolo, for example, is almost exclusively cane pruned. The variety has low distal bud fertility, such that the first two buds on new wood are as good as infertile, often producing no fruit. If Nebbiolo in Piedmont were spur pruned, the plant would in most cases not produce fruit. In classic cane pruning, a fruiting cane and a ‘renewal spur’ are selected. However, opposed to considering the 2-bud spur selected each year as a renewal spur, Tom opts to view this selection as the continuation of a perennial structure. Simply put, the current year’s renewal spur is born from that of the previous year, ‘spur on spur on spur on spur’ year after year. By viewing the selection in this way, Tom is forced to ask himself how that decision affects the next, and thus the next and so forth.

As well as selecting two appropriate spurs to continue the vines’ structure (positioned 180 degrees to one another), Tom also selects a healthy fruiting cane, which is pruned to an appropriate length and number of buds (bud load). ‘Each bud I leave, I leave for a reason’ he explains. To decide bud load, Tom looks at the one-year-old wood grown during the previous season, each strong and healthy shoot is considered as a bud that should remain for the next, this method of fruiting cane selection is sometimes referred to as charge counting. If the plant has produced 10 healthy shoots during the previous season, Tom leaves 10 buds for the coming season between the fruiting wood and the renewal. If he sees that one of the shoots is displaying excessive diameter then 7 may become 8 or 6 become 7.

By determining length this way, Tom is able to observe and respect what the vine has been able to produce under its current constraints, thus seeking a more optimal, balanced yield. Again, a particularly important decision with a vigorous variety like Nebbiolo. ‘This is a heavy investment’ Tom admits, though also noting that the quality of new wood produced just one year after applying these considerations is greatly improved. Both he and Philine have noticed in their vines in Preda that their new wood is stronger, denser and less crunchy when cut. Furthermore, Tom notes that by pruning this way, the overall structure of the vine is simplified, making subsequent pruning work more straightforward and intuitive.

For Tom, the ideal pruning is that which requires the minimum annual removal from the vine. The true value in this renewed philosophy toward pruning becomes glaringly obvious, each year you make decisions that determine at the very least the next 3 years of growth, and thus what you are required to remove.

The sap must flow

As the vine awakens from dormancy, xylem vessels transport sap (containing mineral ions) throughout the vine. These same vessels continue to transport sap for the duration of the vine’s life. The vascular bundles containing xylem vessels, line the outer edges of the trunk and stem, meaning external/outward facing tissue is more directly fed by the flow of sap demonstrating why pruning to outside structures is an obvious choice in working with this natural flow. Winter pruning requires the pruner to make a number of cuts. Both the position and nature of these cuts should respect the physiology of the vine as to not impede sap flow, reducing the volume of dead wood and subsequently the likelihood of wood disease (such as Esca)

After a cut is made, necrotic tissue begins to develop, this dead tissue extends into the trunk of the vine in a cone structure known as a desiccation cone. If the pruner is not careful, this can cause irregular and laboured sap flow. The older the wood that is cut, the larger and deeper the desiccation cone. If a fruiting cane or spur is left in the middle of a bunch of large cuts, sap flow can be reduced to a trickle.

Consider that the plant’s capillary system is hydraulic, where large cuts are made sporadically without consideration of the vine’s physiology, the distance sap is required to travel through that hydraulic system quickly grows, becoming increasingly more strenuous, and thus decreasing alimentation. Consider that the distances covered during both a 100m sprint and a 100m hurdles race are identical. Despite this, the workload required of the hurdler as well as the time taken to complete the race is greater, given the more convoluted path to the finish line. Poorly-positioned cuts, both immediately and those compounding over time can be considered hurdles, forcing both sap and water to take a more protracted route, resulting in poorer alimentation than could be achieved if placement were considered with respect to the vine’s physiology as noted above. The more direct and free of blockages the route to the point of alimentation is the better. Just as a kinked hose produces a meagre flow compared to one without a kink (despite identical pressure in the system), the vine struggles equally in delivering nutrition. Establishing a structure over time through branching support this philosophy. Examples of poor spur placement can be seen below.

For this reason, it is important to separate both the cuts and thus the desiccated area, from primary vascular flow to green, developing tissue. Cuts should be small and precise, on one or two-year-old wood, reducing the size of the wound and leaving an area of protective wood to serve as a defence. This same principle applies to removing crown buds. The reason for this is twofold. Even where a vine has a well-established permanent structure, you may at some point need to return to the trunk, if the crown buds have been removed you may well have snookered yourself. Avoiding the removal of the crown bud also reduces the size of the wound and the proximity of the desiccation cone to the desired sap flow.

Seeing pruning as a perpetual cycle as opposed to a single-season task guides Tom in making cuts which don’t negatively impact sap flow while helping sculpt the vine according to its own physiology. Selecting the continuation of the structure ‘spur on spur on spur’ means cuts to last year’s wood can be made along the top of the vine. Leaving a small area of additional wood, opposed to cutting right back to the cane, provides space for the desiccation cone to form without impeding sap flow. Making smaller cuts in the right places allows for the generation of more living wood, thus allowing for more efficient sap flow and improved alimentation of emerging life and fruit. Furthermore, this method of pruning is said to result in more reliable cane homogeneity as well as balanced bud break, again favourable in varieties like Nebbiolo which prioritise distal buds.

Use it or lose it

In Piedmont, Nebbiolo is exclusively trained to unilateral Guyot, spur and fruiting cane placement are often inconsistent, lacking an overarching blueprint, opposed to being selected such that they instruct the formation of a healthy structure. This oversight is led in part by the view that a single spur and fruiting cane are selected solely to provide fruit for the following season. Though they often continue to produce fruit (the vine is a hardy plant), old vines pruned this way often display large trunks possessing only a small portion of healthy living wood. As the vascular bundles containing xylem vessels draw sap through the lower wood, they in turn provide sustenance to the permanent wood structures. Where the vines workload is neither balanced nor uniform (a result of inconsistency) a portion of the trunk essentially dies, impeding sap flow through the trunk, resulting in a mass of dead wood and a less healthy, resilient vine more prone to wood disease. 

Combatting this issue is relatively straightforward, stemming first and foremost from a shift in seeing pruning as more valuable than only the provision of that season’s fruit. Where possible pruners could within this methodology select two spurs, one on each side of the trunk, and a fruiting cane from one of the previous years spurs. This type of placement not only helps guide the formation of a structure that is easier to work with but also places more universal demand on the xylem throughout the trunk, in turn retaining more living wood, allowing ample sap flow and reducing the risk of wood disease and a need for replanting. Numinous though it may be, both quantitatively and economically a vineyard of healthy, coetaneous vines is more ideal than one composed of vines of mixed ages.

Nebbiolo is a particularly vigorous variety requiring substantial vineyard work to maintain a manageable canopy and yield fruit suitable to meet the demands of its greatest wines. Capable of yielding fruit of enviable quality for many years, much is demanded of old vines in the Langhe. Demand notwithstanding, pruning is often treated as independent of vine health and longevity, often viewed instead as a task intended to make possible the production of fruit during a single season. This perspective represents an oversight, a missed opportunity to shape the vine, reduce the need for damaging cuts, balance yields and bud development, strengthen the vines innate resilience to disease and drought and reduce the likelihood of wood disease. Instead, where pruning is considered as fundamental to vine health, where each interaction is considered within the entire lifecycle of the grapevine, a wealth of benefits can be realised. By working with the vines organic growth patterns and respecting sap flow the vine retains more living wood, canes demonstrate improved homogeneity, fruit ripening is more even, vigour more manageable, and vines are more resilient, and more suited to withstand the demands of cultivations.

Tom Myers has worked as both a consultant and an employee at a number of notable wine estates. He credits the work of François Dal, Simonit & Sirch, and Marceau Bourdarias in motivating his own application, teaching and advocacy of Poussard pruning. Having seen this methodology in practice at Rinaldi, Lamy, Bouley, Lachaux and more, Tom now cultivates his own vines according to its principles. Philine Dienger has worked at biodynamic estates across Europe as well as spending time as a consultant at Simonit & Sirch. Both Philine and Tom cultivate vines in the Barolo MGA, Preda.