Pruning and Training Grapes in the Home Vineyard [fact sheet]

grapes

Introduction

Home-grown grapes make excellent fresh eating, juices, jellies, raisins, and wine. A small home vineyard with even just a vine or two can be a beautiful and productive addition to the landscape, yard or patio.

For more complete information about choosing varieties and establishing a small home vineyard, see our publication Growing Grapes in New Hampshire. In this publication, we discuss the importance of pruning and training grapes, and describe some of the training systems that can be used successfully in home vineyards.

Why prune and train grapevines?

Grapevines produce fruit on new growth each year. Because healthy vines grow several feet per year and would naturally set far more fruit than they can ripen, they must be pruned each year when they are dormant to keep the vines producing fruit and to keep them from taking over an ever increasing space. During the growing season, vines are trained to maintain a particular shape and to ensure that fruit are exposed to sunlight and airflow.

Vocabulary

        Shoot –the current season’s growth (has leaves, tendrils, and fruit clusters)

        Cane –a one-year old shoot(each bud on a cane produces a shoot)

        Spur –a cane pruned to 1-3 budsTrunk –a permanent main stem that supports the fruit-bearing                     wood

        Cordon –semi-permanent branches off of the trunkTrellis –the physical structure used as support                          for grapevines

There are countless named pruning and training systems for grapes used throughout the world. Some training systems are better suited to certain cultivars, certain climates, and certain uses, than others.

Some of the basic differences between training systems relate to:

1) whether fruiting shoots are borne on long canes that are replaced each year or whether they are produced from spurs on cordons that live for many years, 2) the height of the permanent trunks, which determines whether the fruiting zone is high (6-7 feet off the ground), low (3’ off the ground) or something in between, and 3) how the fruiting shoots are maintained throughout the growing season. The training system chosen determines the type of trellis that you will need.

In colder climates, cane-pruned systems are often better than cordon-pruned systems because they are less susceptible to winter injury. Similarly, shorter trunks are less likely to experience winterkill. We’ll discuss four systems that can work well and that are easy to implement in home vineyards in cold climates.

The table below suggests training systems that are suitable for several cold-hardy grape varieties. Note that it is possible to grow vines using training systems other than those recommended, depending on your preference.

 

                                                                     

 Varieties

 

Grapes trained to a VSP (vertical shoot positioning) system.

The grape trellis

Grapevines require support, which is most often provided by a trellis. The trellis must be strong and substantial enough to carry the weight of the vines plus a heavy crop during strong winds.

It is important to choose your training system before you build the trellis. A typical trellis consists of firmly-set, well-braced posts at intervals of 10 to 15 feet along the row. Set end posts at least 3 feet deep leaving 6 feet above ground. End posts should be well-braced or angled outward to prevent pulling by the taut wire coupled with the weight of the grapevines. (See Trellis End Post Assembly Designs for Vineyards for more details about trellis design).  

Both the VSP/Guyot and Kniffin systems require posts with wires set at varying heights (see below). In addition to the posts, the Munson system requires arms at each support post so that it can support four wires along the lenth of each row.  The arms can be moveable (this system is then called the “modified” Munson system) or permanent.

There are many designs for grape arbors, including several designs for relatively simple construction from readily available materials. It is important to remember that grapevines are heavy, and an arbor for grapevines should be of solid construction.

Pruning and training

Prune only in late winter or early spring, since early winter or fall pruning can promote winter damage. Vines pruned in late spring just prior to bud break will “bleed,” but this does not harm the vine. Fruiting canes should be tied to wires before buds begin to swell because buds are easily rubbed off once growth begins.

For all of these systems, the first two years are similar. During the planting year: Prune the newly-set plant back to two strong buds. Allow all shoots to grow and tie them loosely to a stake (Figure 1). One year after planting: Prune back to 1 or 2 strong upright stems, which will become the trunk(s). Having two trunks is insurance against winter injury.Tie one or both trunks to a training stake that is firmly attached to the bottom wire (Figure 2).  

 

Figure 1: The planting year. A newly set plant (left), immediately after pruning (center), and several weeks after planting (right).

 

Figure 2: The year after planting, just before dormant pruning (left), and after dormant pruning, where two canes have been chosen to become trunks (right).

I. Vertical Shoot Positioning (VSP) and Guyot Systems.

The vertical shoot positioning (VSP) system (Figure 3) is best suited for varieties with an upright growth habit. It produces a vertical hedge of leaves with a fruiting zone below, about 3 feet above the ground. It uses a single support wire approximately 30 inches above the ground, with three pairs of catch wires set at 1-foot intervals above the support wire.

Two years after planting: Select 4 vigorous canes for the arms. Select 2 for the left side, and 2 for the right side, as shown below. Choose canes that form just below the point where the lowest wire and trunk meet. Prune each cane/arm to 10 buds in length and tie them loosely along the wires. For each of the 4 arms, a two-bud-long renewal spur should be left on the trunk to produce fruiting canes for the following season. Remove all other canes.

Each dormant season thereafter: Replace the arms with canes and leave new renewal spurs. This annual pruning will help ensure consistent production and high fruit quality and will keep the vines at a manageable size and shape.

Throughout the growing season: As the new shoots grow, tuck them between each set of catch wires to encourage them to grow straight up. After the fruit clusters have set, remove up to two bottom leaves from each new shoot to increase light exposure to the fruit clusters.

The guyot system is a variation of VSP that only has one fruiting arm each year; each arm extends in the same direction. In this system, vines can be spaced closer together (40” apart) in the row. The guyot pruning system is an easy one for home vineyards, and is thoroughly described in our publication ‘An Easy Training and Pruning System for Home Grape Vines’.

 

   Figure 3: The VSP (vertical shoot positioning) (left), and the Guyot (center) systems, after dormant pruning. On the right, the VSP after new shoots have been tucked betweenpairs of catch wires during the growing season.

II. Munson System.

The Munson System (Figure 4)  is well-adapted to vigorous trailing varieties that benefit from sun exposure to the fruit. The trellis for this system requires supported cross-arms at each post to support four high wires (5-6 feet above the ground), in addition to a single support wire 3 feet above the ground. If the cross-arms are moveable, this system is called “Modified Munson”.

One year after planting: Tie trunk(s) to the top wire. If they are not long enough to tie to the top wire, tie to the bottom wire and extend a new shoot to the top wire the following spring.

Two years after planting: Select 4 vigorous canes for the arms. Select 2 to grow towards the left, and two to grow towards the right – each along one of the support wires. Choose canes that form just below the point where the wire and trunk meet. Prune each cane/arm to 10 buds in length and tie them loosely along the wires. For each of the 4 arms, a two-bud-long renewal spur should be left on the trunk to produce fruiting canes for the following season. Remove all other canes.

Each dormant season thereafter: Replace the arms with canes and leave new renewal spurs. This annual pruning will help ensure consistent production and high fruit quality and will keep the vines at a manageable size and shape.

Throughout the growing season: As the new shoots grow, train them outwards and tie them loosely to the outer catch wires. This will create a trailing curtain of shoots. After the fruit clusters have set, remove up to two bottom leaves from each new shoot to increase light exposure to the fruit clusters.

 

Figure 4: The Munson system after dormant pruning (left), and after new shoots have grown and been combed over the catch wires during the growing season (right).

 

III. Umbrella and Four-arm Kniffin Systems.

The four-arm Kniffin System (Figure 5)  is well-adapted to vigorous and trailing varieties. It uses a two-wire trellis: attach two strands of No. 9 or No. 10 wire to the posts – one at 3 feet and one at 5-6 feet above the ground.

One year after planting: Tie trunk(s) to the top wire. If they are not long enough to tie to the top wire, tie to the bottom wire and extend a new shoot to the top wire the following spring.

Two years after planting: Select 4 vigorous canes for the arms. Select 2 for the top wire, and 2 for the bottom wire, as shown below. Choose canes that form just below the point where the wire and trunk meet. Prune each cane/arm to 10 buds in length and tie them loosely along the wires. For each of the 4 arms, a two-bud-long renewal spur should be left on the trunk to produce fruiting canes for the following season. Remove all other canes.

Each dormant season thereafter: Replace the arms with canes and leave new renewal spurs. This annual pruning will help ensure consistent production and high fruit quality and will keep the vines at a manageable size and shape.

The umbrella Kniffin system is a variation that features four long canes, all starting at the top wire. This distributes growth more evenly than the four-arm Kniffin system, and maximizes sun exposure to the fruit. It also provides a bit more of a solid curtain of foliage than the four-arm kniffen system. This system differs only slightly from the four-arm system, as described below:

Two years after planting: Select 4 vigorous canes for the arms. All four canes should form just below the point where the wire and trunk meet. Prune each cane/arm to 10-12 buds in length and loop them up and over the top wires, and then tie each one securely to the middle wire so that each forms a gentle arc shape.

Figure 5: The Four-arm Kniffin (left) and Umbrella Kniffin (right), after dormant pruning.

IV. Arbors.

Grapes can be allowed to cover arbors naturally without regular pruning. This requires little effort, and the vines will likely produce good shade, but relatively few fruit. In certain situations, fruit can be a nuisance in that they encourage birds and fall to the floor, making a mess. If your priority is shade rather than fruit, it is possible to choose sterile (or all-male) grapevines for an arbor to minimize pruning maintenance and to prevent fruit production.

If your goal is to produce fruit as well as shade, pruning will increase your chances of success. Unlike the other systems described in this publication, we describe a cordon-pruned system to cover an arbor. The benefits of this system are that the permanent arms (or cordons) are supported by the trellis structure, and the weight supported by the middle of the structure is minimized.

If pruned regularly, assume that a single vine will reach out at least 4’ in all directions from the main trunk. For an arbor that is 8’ long and anywhere from 6-8’ wide, consider planting four vines, as shown in Figure 6.

One year after planting: Prune back to 1 or 2 strong upright stems, which will become the trunk(s). Tie trunk(s) to a support stake to train them straight up a corner post of the trellis. If they are not long enough to reach the top, extend a new shoot to the top the following spring.

Two years after planting: Establish the arms, or permanent cordons, along the sides of the arbor. You may select as many as 2-3 canes to become arms, depending on the construction of your arbor. Each cane should be supported by the arbor. Shoots will grow out perpendicular to the cane during the growing season.

Each dormant season thereafter: On each arm, aim to choose one fruiting cane (4-6 buds long) and one renewal spur (with 2 buds) per linear foot along the arm. Remove all other canes. This annual pruning will help ensure consistent production and high fruit quality and will keep the vines at a manageable size and shape. Figure 6 shows what the mature vines would look like, immediately after spring pruning.

 

                  Figure 6: Four grapevines on an arbor system, after dormant pruning.