Trellising Grape Vines

Trellising the Grape:
An Unsung Aspect of Wine Quality
By Cole Danehower

Most wine drinkers never think about how the grapes that made their wine hang on the vine. Yet every winemaker worries intensely about the details of how to best trellis their vineyard vines in order to get the optimum ripeness for their grapes. Grape vine trellising is, for us consumers, an unsung yet vital component of what we finally taste in the bottle.

Wine and Sun

Hot Southern Oregon vineyards
get lots of sun

One of the world’s foremost experts on wine grape growing, Dr. Richard Smart, has written that “wine is a product of sunlight.” It follows, then, that to get the best wine the winegrower must make the best use of sunlight. Trellising—how the grape vine is trained to grow on wires or posts to expose its leaves and fruit to the sun—is a key tool in achieving this goal.

Wine is essentially the product of photosynthesis. The vine’s leaves gather sunlight to fuel the process of converting carbon dioxide in the atmosphere to sugars in the fruit. Additionally, the ripeness, color, and flavor characteristics of the grape berry itself are influenced by how much direct sunlight it receives.

It follows, then, that in order to achieve the best possible fruit, the winegrower must manage the way in which his grape vine’s leaves and fruit are exposed to sunlight. This is the job that trellising performs.

Yet, there is no single “best” trellising method, and diligent growers often tinker continuously with how their vines grow in order to learn what works best for their particular vineyard.

Over the many generations of wine history around the world, a number of different trellis systems have been adopted as worthy methods of capturing sunlight. These trellising variations are based on the unique needs of different sites to manage factors such as weak or strong vine vigor, to best capture the sunlight at different exposures and latitudes, and even to make harvesting easier.

Canopy Management

It is obvious to any wine drinker that the climate of a growing region—what is called the macroclimate—has a lot to do with the quality of wine that can be made there. It is perhaps less obvious that each individual vineyard site also has its own climatic variations—its mesoclimate—based on local conditions such as slope, exposure, wind, rain, etc.

What few wine drinkers realize is that there is also a third kind of climate that influences the quality of the wine they drink: the microclimate that exists within the above-ground canopy of vine leaves and fruit out in the vineyard. The quality of the climate immediately surrounding each plant is very important in how the plant grows and matures its fruit, and in the final character of the wine that is produced. Trellising is also the most important tool in managing this canopy microclimate for the best fruit quality.

The ideal in canopy management is to find for each vineyard an arrangement of vine leaves on the trellis that balances the many factors that influence fruit quality—and therefore wine quality. These factors include things such as: the number of shoots per vine and the way in which they are placed on the trellis guide wires, the number of leaves per shoot and their orientation to the sun, the number of grape clusters per shoot and their shading within the canopy, as well as many other factors.

Each different trellising system offers growers varying opportunities to influence the fruit quality through canopy management.

Trellis Systems in the Pacific Northwest

As anywhere else in the world, there is no “best” trellis system for the Pacific Northwest. Different climate conditions (warmer or cooler), soil fertilities (invigorating or devigorating), vine characteristics (own-rooted or rootstock), and varietals (early ripening or late ripening) all require different approaches to trellising in order to achieve vine growth balance.

Even so, a number of different trellising designs have come into use around the Pacific Northwest as ways to help improve the quality of our grapes, and therefore our wine.

Guyot Training

Often the highest quality wine comes from vines planted in thin, relatively infertile soils. This means that the vines will tend to have low vigor, which is desirable because the plant will tend to put the majority of its energy into reproduction (creating fruit) rather than simply expanding (growing larger).

The Guyot system, named after Dr Jules Guyot, a 19th century French scientist, is one of the most commonly used trellis systems in many of the world’s fine wine regions, and is frequently used in Oregon, Washington, and British Columbia because it is well suited for low yield farming.

Though there are many subtle variations, the basic Guyot design is relatively simple and easy to manage. It also has the flexibility to allow easy modification based on local conditions, and has the important advantage of producing small yields of high quality fruit.

From the vine’s trunk, usually two fruiting canes are trained to grow in opposite directions along guide wires that run just above the trunk. Shoots that emerge from the canes are trained to grow upwards by clinging to catch wires located above the canes.

In this system shoots can be manually placed for optimum spacing and exposure to sunlight, and the fruit clusters can hang below the leaves, receiving the benefits of good air circulation and controlled exposure to direct sunlight.

Vertical Shoot Positioned Trellis

Similar to the Guyot system, the Vertical Shoot Positioned trellis (often abbreviated as VSP) is designed to arrange shoots to grow upwards across guide wires. Usually four fruiting canes are trained to grow in opposite directions along two levels of wire. As in the simpler Guyot, fruit hangs 3-4 ft. off the ground, and below the raft of vertically growing leaves (see photo).

Scott Henry Trellis

The Scott Henry Trellis system can be considered a “native” Northwest trellis design! Grower and winemaker Scott Henry (owner of Henry Estates, in Umpqua, Oregon) developed this dramatic variation of the vertical shoot positioned trellis as a way to deal with the fertile soils in his vineyard.

Because the Henry Estate vineyards are located on productive soils in the Umpqua River watershed, Henry had to find a way to encourage his plants to better ripen more fruit, when all they really wanted to do was grow more shoots and leaves.

Henry’s approach was to modify a VSP trellis by dividing the canopy into two sections. Two of the four fruiting canes have shoots that are trained to grow vertically upward (as in a normal VSP system). The remaining pair of canes have shoots trained to grow downward, thereby splitting the canopy into two sections (see drawing).

The Scott Henry Trellis creates additional leaf surface area with which to feed the fruit, because the upward and downward trained shoots mean each cane’s leaves are more clearly open to the sun. This also means the density of the canopy is lessened, thereby reducing disease pressure and exposing more of the fruit.

Reproduced with permission from Henry Estate - Thanks guys!

Cordon Training

This system is one of the most popular ways of training grape vines, and is more used in the warmer growing regions of Washington (and in California) than it usually is in Oregon. This training approach produces an arm of the vine permanently growing along a bottom guide wire, with shoots emerging from the arm and trained vertically along additional wires. Often, the shoots are trained to droop over the top wire, with the grape clusters hanging roughly in the middle of the canopy.

GDC Trellis at Academy of Wine

Geneva Double Curtain

This rather more complex trellis design is rarely seen in new vineyards, though a number of older Northwest vineyards (particularly in the warmer growing regions) sport it. In this design each plant is made to grow two trunks, whose cordons are trained across twin guide wires at a relatively high level from the ground. Shoots are then allowed to grow hanging downward, curtain-like (see photo).

Like the Scott Henry system, the Geneva Double Curtain (GDC) divides the canopy, thereby increasing overall exposure yet minimizing canopy density. Also like the Scott Henry, the shoots are trained downward.

Lyre Trellis

Lyre, or U Shaped Trellis

This approach to trellising is also uncommon in the Northwest, but even so, some very fine wines have been produced using it. In this design the vine is divided into two fruiting canes, each growing in opposite directions, with shoots arranged to grow vertically upwards across wires threaded through a U-shaped support system.

Like some of the other systems described here, this approach results in a divided canopy—which means (as we have seen) less density because the leaves and fruit are spread across two curtains, increased sun exposure, and fruit that is open to air movement, yet protected from sunburn (see photo).

Though an understanding of trellis styles is hardly necessary to the enjoyment of Northwest wine drinking, a knowledge of how the grapes grow can help deepen your appreciation of the experience. And, the next time you visit a winery or vineyard, take a moment to study the vineyard. Can you identify which trellis system is being used? Why not ask the winery people what they know about the trellis—and how they think it influences the character of the wine they make?