Cordoned off - a look at vine-training
A neatly coiffed and manicured vineyard in Bordeaux or Burgundy with barely a leaf out of place rather belies the true nature of the grapevine. It's a climbing plant whose natural tendency is to ramble about until it finds something it can scramble up, clinging on with its tendrils and leaf stems, until it can get its leaves out into the sunlight.
Uncontrolled grapevines can put on metres of growth in a single season - even the müller-thurgau vine in my own garden can throw out 2 or 3-metre shoots before you can say 'pruning shears', or so it seems.
As with most things wine-related, a lot of complex vocabulary has been developed over centuries, sometimes seeming to bamboozle rather than enlighten, so this article is an attempt to clarify what is really going on with techniques like Gobelet, Guyot and Geneva Double curtain.
Vine training and pruning methods are first and foremost about pragmatic farming - a vineyard would be impossible to manage efficiently left to itself, as grapevines wander so freely.
Vines also have a tendency to grow shoots and leaves rather than fruit when growing conditions are good. So, one important aspect of vine training is about imposing disciplined growth patterns on the vines so they can be managed by people, or increasingly by machine.
Then it's about using a combination of science and tradition to produce consistent yields of the healthiest and best quality fruit possible. This requires even crop loads, a balanced leaf canopy (in other words enough leaves to ripe the grapes and enough fruitful buds to provide the right crop level - research suggests around 0.8 to 1.2m2 of leaf canopy per kilogramme of grapes), good exposure to the sun and plenty of aeration to avoid fungal diseases.
As you might guess there is a multitude of options available to the grower - who needs to think carefully when planting as a vineyard may have a commercial life of 30 to 40 years.
First: training the trunk of the vine
The first part of the process is about training the permanent structure of the vine - its woody trunk. And while in the wild, a vine would be off scrambling up trees and benefitting from this support (still a system in use occasionally in Italy), with a few years of careful pruning and training, vines can develop fairly much self-supporting woody trunks.
The basic options are two-fold: head-trained vines have an upright (more or less) trunk ranging from just a few centimetres high, to around a metre or more. There are no permanent horizontal side branches here, but young canes or spurs renewed every year.
High trunks take the fruiting zone and buds away from frost risks close to the ground and make vineyard work less back-breaking, but also lose the benefits of soil warmth to help ripen fruit.
Cordon-trained systems take this further by establishing a trunk with one or more permanent woody 'arms', typically supported by trellising.
The question of pruning
Once the basic architecture of head-training or cordon-training (in whatever exact form it takes) is in place, growers need to decide whether a vine will be cane-pruned or spur-pruned.
The canes or spurs are the renewable parts of the grapevine's system and will be replaced via the winter pruning system every year. The main difference here is that spurs are short stubs with two to three buds while canes are longer, and typically have around six to twelve buds.
Cane pruning is particularly useful for certain varieties of vines that don't produce fruit from buds very close to the trunk (For instance in Valpolicella, corvina is notorious for this so-called basal bud infertility).
During the pruning process, workers will cut off all the surplus vine branches from the previous season, just leaving the material required for the next harvest, plus a spare for the year after.
In fact, growers can weigh the material cut off a vine (also known as pruning weight) and use it as a measure of how much growth the vine put on in the past season. This gives an indication of vigour and therefore how much crop a vine can ripen.
Cane pruning requires higher skill levels as a suitable, thick healthy and fully lignified cane (basically nicely brown and woody rather than green and still soft) must be selected, and then tied down to a trellis wire.
In some variations of cane pruning, these may be tied in arches or even curved all the way back to the main trunk - the idea here is to break so-called apical dominance and ensure even bud-break and growth along the cane. (Apical dominance happens in most plants where the very highest bud produces plant hormones to stop lower buds from growing, so the plant's effort can go into getting taller rather than growing side branches).
Cane pruning also requires a short spur to be kept - which will provide next year's cane or canes. In cordon systems, usually spurs of two to three buds are kept, evenly spaced along the cordon so this doesn't need so much skill and indeed can be at least partially mechanised.
The Guyot method of vine training
One of the wine world's most popular training systems is the Guyot method, popularised by Charles Guyot in the 1860s. This is a head-trained system with a permanent main trunk, plus one cane and a spur for a single Guyot, or two canes and spurs, for the double Guyot.
The canes are tied into wires and then the buds on the cane grow into the vine's canopy and fruit for that year. Usually the canopy is then further trimmed and tied into trellis wires in a method known as VSP or vertical shoot positioning. This allows good exposure of leaves to the sun for photosynthesis, and an evenly spread fruit zone close the trellis. The canopy may even be topped or hedged by machine to keep leaf growth in check and help ensure good fruit ripeness.
The Guyot suits most soils and vineyard zones - except where soils are rich and vigorous vine varieties being grown, where lots of leaf growth can mean crowded canopies. This leads to shaded leaves become a drain on the vine's resources as they can't photosynthesize without enough light, while shaded fruit is pale in colour, green and herbaceous in flavour and often with excessive potassium levels (which creates problems with colour and ageing ability).
A variation that suits vigorous vines is to use a divided canopy system to allow better leaf exposure, for example the Scott Henry system where the canopy is divided into two by movable wires so half the canopy is trained downwards below the fruit zone.
Bush vines or the Gobelet system
The other common head-trained system is the bush vine or Gobelet (so called as it is supposed to resemble the shape of a wine glass or goblet). This is usually a short trunk (sometimes multiple short trunks) that is pruned with spurs, then the shoots may grow upright or sprawl depending on the variety, or may be tied to a single stake.
It's mostly used in warm dry Mediterranean areas like the Languedoc, Cyprus, Croatia or central Spain where shading and fungal disease is not such a problem and indeed protection from sun burn is useful. It doesn't need expensive posts and wires - but also can't be mechanised.
Bush vines tied to a stake in Hungary.
Old bush vines, Dom Gauby, in the Roussillon.
Old bush-trained vine in Cyprus showing why it gets the name 'Gobelet'
Grapes on a wire
Of the cordon methods, there are many variations. Smart Dyson is a modern split canopy version where cordons are pruned so that alternate spurs point upwards and down, Geneva Double Curtain has up to 4 cordon arms with canopies trained downwards, Sylvoz is a cane pruned version used in the Veneto region, with canes trained downwards, Lyre has the woody arms trained into an open U-shape to allow light into the canopy centre, and there are many more.
In Eastern Europe, many of those wines we enjoyed in the 1980s and early 1990s were on large cordons designed to allow use of huge Soviet tractors between vines. And yet another type of cordon system is the pergola (also known as tendone in Italy, or parral in Argentina). There are mixed views about this system as the vines are trained above head height and the grapes hang down under the shade of the canopy. Some top Italian producers in the Veneto region are returning to this traditional approach as they believe there's a closer match between sugar ripeness and flavour ripeness.
Matching method with site
Whichever method producers choose, it has to suit their soils, their site (e.g. very steep slopes like Mosel valley can't have trellis installed - it's simply not practical) and the grape variety itself (especially how vigorous it is) to ensure that crop load and leaf canopy are balanced, plus availability of people to do the work or machines.
Then there's risk of frost damage or fungal disease, sunburn, the producer's ambitions for quality or volume, and finally in certain appellation regions you may simply have to do as the rules specify. And the producer is pretty much stuck with these decisions for the next several decades so well worth some detailed thought.