Training systems for cold-climate grapes

The final shape of a grapevine is determined by how its arms are trained. Some are trained into more permanent structures (cordons); others are rotated annually through pruning.

The trellis system is the hardware that supports the training of a grapevine into a particular shape. One type of trellis, or slight variations on its design, can be used to support multiple training systems.

For practical purposes such as ease of harvest and labor, it is uncommon to see multiple training systems on a single trellis.

Most wine grapes grown in Minnesota are trained as bilateral cordon grapevines on two-dimensional trellises using either a High Cordon or Vertical Shoot Positioning (VSP) training system. This means that the grapevine will go through three years of training to establish one to two permanent trunks, two arms (i.e., cordons), and fruiting spurs.

Variations in training systems

Training systems are important for grape quality. There are several variations in training systems; all come with advantages and disadvantages.

There is no wrong way to train a grapevine, but growers should consider their overall production goals and their workers’ needs when it comes to comfortably working on and harvesting grapes.

Training systems vary based on:

• The direction in which shoots are trained (most commonly upward or downward).
• The height of the fruiting canopy.
• Whether they are two- or three-dimensional.
• The number of canopies (single or double).

Shoot direction

Training systems can support canopies with shoots trained either upright or downwards. Because cold-climate grapes vary in their growth habit from upright to semi-upright to trailing (procumbent), choosing a training system that works with a specific grape variety means you won’t have to fight against its natural growth preferences.

For example, varieties that tend to trail may be very difficult to establish upright spurs, and their shoots may be more prone to slipping out of trellis catchwires. However, after spurs are established, this problem may lessen over time.

In addition to affecting the growth habit, the shoot directly affects how the clusters are positioned and exposed to light.

Downward training systems can make hand-harvesting grapes more difficult, as the shoots are more likely to hang over the clusters. Diseases that overwinter on older wood may wash down onto developing shoots because the shoots are positioned below the cordon. This is less of a problem for cane-pruned grapevines.

Canopy height and size

The actual trellis height partly determines canopy height; however, the training system used can limit how tall the canopy can grow.

For example, systems with upward-trained shoots tend to have shorter canopies with less leaf area because the trunk takes up space, and the canopy height is limited to the point where the fruiting wire is positioned up to the top trellis wire.

In contrast, downward-trained systems that hang below the cordon can take up more space because they can grow to the length of the trunk, which starts at the top wire and ends just above the ground.

Grapevines with taller cordons and fruiting zones have an advantage in spring frost conditions, when taller canopies are more likely to be a few degrees warmer than fruiting zones that are closer to the ground. Tall canopies can be an advantage in this sense, but very tall canopies can be challenging to prune and manage without a trailer or other equipment. 

Grapevine dimensions (two- or three-dimensional)

The dimensions of a grapevine impact how the fruit hangs within the canopy. Grape clusters growing in two-dimensional systems are more likely to be crowded by shoots and lie on the trellis wire.

Three-dimensional systems allow fruit to hang freely, which can increase the overall cluster quality.

Number of canopies (single or double)

Training systems can support either single canopies (most common) or double canopies to maximize production, which can help vineyards planted on highly fertile soils that lead to excessive shoot and canopy growth.

Double canopy systems can be split horizontally, as is the case for systems like Munson types and Geneva Double Curtain, or vertically, like the Scott Henry system.

The key to working with a vertical split system is to ensure that canopies do not overlap each other, meaning the top canopy has shoots trained upward, while the lower canopy has shoots trained downward.

Training system classifications

Grapevines can adapt to different training systems, which can be noted worldwide as regions adopt systems specific to their climate and the resources available.

Some systems, like fan training or pergola training, may be more appropriate and doable for small vineyards, community gardens, and backyard settings.

The systems listed below are the most common and practical for commercial production.

Two-dimensional training systems

High Wire Cordon (HWC)

The HWC system is trained upward with a permanent trunk that supports a bilateral canopy (two arms that each support a canopy on the left and right side). When it is cane pruned — the arms are renewed each season — this system is commonly referred to as Umbrella Kniffen.

HWC can have very large canopies depending on how tall the trunk is, and simply requires a single top wire that runs across the top of the trellis.

As shoots reach the ground, they benefit from a practice called skirting, where shoots are trimmed just above the ground to prevent them from getting in the way of equipment and getting dirt splash from vineyards with bare ground.

It is common for the fruiting wire and cordons to be positioned from 5.5 to 6 feet. While these can be positioned at a taller height, it is not recommended for ease of working.

Vertical Shoot Positioning (VSP)

An upright system, VSP tends to have a shorter trunk than the HWC system and an altogether shorter canopy. The upright shoots require a number of wires to guide them up to the top wire. This can be done by attaching shoots to single wires or placing shoots in between catchwires, which is easily done by tucking the shoots in at the right time.

VSP vines will usually need to be summer pruned or hedged to prevent the canopy from falling over and overlapping itself, which can lead to shading. Careful attention should be given to timing, as early hedging can lead to excess growth and the need for multiple passes of hedging.

The VSP system places the fruiting zone at a lower point (around 3.5-4 feet), which is often conducive to hand harvesting, as clusters hang more openly than with the HWC and GDC systems.

For growers concerned about spring frosts, the canopy height can be brought up higher, although this will shorten the total canopy area unless a very tall trellis is installed, which is less common.

Scott Henry

Scott Henry is a vertically split double-canopy system that can decrease overall vine vigor. It should only be used for sites planted on highly fertile soil, such as a site that rotated off an alfalfa field.

As mentioned above, the key with Scott Henry is to train the upper canopy upwards and the lower canopy downwards. This often leads to a double canopy system that has less leaf area than either an HWC or VSP system, but can be adapted to a taller trellis height to extend both canopy heights. 

Three-dimensional training systems

Munson

Munson is a three-dimensional system with a cordon that grows along the top wire. Shoots are given an extra training wire that extends outside the canopy, allowing them to extend out and clusters to hang down freely without compression from their shoots.

The Munson system is supported by a three-dimensional trellis constructed with two cross arms attached to the end and in-line trellis posts that extend at an angle, supporting a single wire that runs down the trellis row.

Similar to HWC, Munson shoots can be trimmed just above the ground to keep shoots from contacting the ground and getting in the way of equipment. 

Geneva Double Curtain (GDC)

An example of a horizontally split canopy system, GDC uses the three-dimensional trellis as a means to train a bilateral cordon on each side of the trellis center. This helps with reducing vine vigor and increasing yields, but does not offer the same support to cluster quality as the Munson system does.

Trellises used to support GDC can be similar in design to Munson trellises; however, the side wires tend to be a thicker gauge to support the weight of each cordon, and when cross arms are used, they need to be reinforced to handle the weight.

Similar to HWC, GDC shoots can be trimmed just above the ground to keep shoots from contacting the ground and getting in the way of equipment.