How to train young grape vines
Grapevines comprise an intensive crop system. Investing time and labor up front is necessary to establish and maintain a vineyard.
Critical interventions during the first three seasons of growing grapevines will help to ensure long-term success. Establishing a strong root system and good plant architecture will support fruit for years to come. The fundamentals of training young vines can be applied to any of the trellis systems. Here we discuss some of the specific needs of growing cold-hardy hybrid grapevines.
After planting, the grapevine requires adequate moisture for growth. The root system in grapes is maintained for years to decades, whereas the above ground shoots (80-90%) are removed annually during pruning. The roots (and trunk) are the permanent vine structure and serve to anchor the vine, obtain and transport water, and source nutrients from the soil.
To ensure success, the young vine should not have to compete with weeds for water, nutrients, or sunlight. Weeds also can harbor insect pests and create micro-environments around the vines that favor disease.
Weed control should be done through mechanical cultivation (hoeing and tilling) and herbicides (a pre-emergent that stops weed seeds from germinating). When vines are dormant, glyphosate (Round-up) could be used to manage weeds, but should be avoided when vines are actively growing as they are very sensitive to sprays, especially 2,4-d and Dicamba broadleaf herbicides.
Irrigation should be provided to young vines at a rate of 1 inch per week, and at intervals to encourage deep roots to penetrate the soil. Frequent watering of low volumes can encourage shallow surface roots that put the vines at risk for drought stress.
Some growers may choose to use grow tubes which protect the young vine from predation and provide a warm and humid microclimate. If used, make sure that the tube is placed into the ground around the vine to get the most benefits and prevent any chimney effect that would cause herbicide damage. Find more information about how to use grow tubes in vineyards.
Figure 1A. A young vine several weeks after planting showing multiple shoots and flower clusters. Notice the bare soil, free of weeds within the row.
Figure 1B. The same vine after pruning to select 2 shoots to train as the trunks in season one. Notice how much growth can be removed. A bamboo stake is placed next to the vine for support and training.
A young vine may produce several shoots in its first season. The goal for the vineyard manager is to select and train one or two of these to become the trunk. This requires staking (bamboo works well) and tying the shoots vertically (Figures 1A, 1B). If training to a high-cordon system, this means training to the top wire; for vertical shoot position trained vines (VSP) or other mid-wire trellis systems, the shoots should be trained vertically to the wire, and then trained to grow along the wire in either direction. Growing two trunks gives the vineyard manager flexibility in selecting the best one to become the main trunk in year two or three. Alternatively, a double trunk can be maintained, which gives more options for rejuvenation in cases of severe winter injury. Some shoot thinning is required in year one to direct the growth, reduce competition due to shading, and create the correct plant architecture.
Vines in their first year may grow as much as 6 to 8 feet, reaching the top trellis wire (Figures 2A, 2B). However, this wood may not harden-off completely before winter and may suffer some winter injury. Some vines may even die to the ground or snow line. However, the critical work was done in the first season through the establishment of a strong root system, and this will lead to considerable (and fast!) growth in season two. Figure 6 shows examples of winter injury where new trunks are being retrained.
Figure 2A. The young vine needs to be fastened to the bamboo stake. Here a Tapener is used. The vine will need to be tied throughout the season as this vine will likely grow to the top wire within the first year.
Figure 2B. Growth after one season, ideally one or two shoots are trained to become the trunk(s).
The goal of season two is to establish the permanent structures of the vine including the roots and trunk.
Establishing the trunk
Pruning should be conducted on the young vines to head back the first season’s growth to remove winter-damaged shoots, increase the vine diameter, and to select the best growing cane(s) to become the trunk. Avoid using “bull canes” to establish a trunk. Pruning cuts should be above the wider portion of the cane just past the bud, which is referred to as the node. The cane should be pruned to a point of the vine where the diameter is about 3/8 inch.
Before growth resumes, herbicides should be used to restrict weed growth within the row under the trellis. New growth should be trained to the stake and brought up to the appropriate wire depending on the trellis system. If a vine has suffered severe winter injury and died back to the ground or snow line, the pruning cut should be made several nodes above the soil level and the vine similarly treated as in season one.
A grower might be surprised as to how quickly this vine may grow because the roots have been established for one year. Remember to grow straight trunks, as the shape of the vine will be maintained for years and can have effects on infrastructure and equipment. A cylinder is a very strong and stable structure, whereas crooked vines can sag and bend.
Irrigation in season two may be required in some situations. The vineyard manager should monitor soil conditions and plant growth to determine if vines require additional moisture.
Weed management within the row is important to reduce competition in season two and over the lifetime of the vine. Pre- and post-emergent herbicides will be necessary to keep the soil bare within the row. This allows the soil to warm quickly in the spring (which grapes respond well to), and has the other cultural benefits already mentioned.
The growth in the second season will quickly grow to the wire and must be trained. If training a single trunk to the top wire, a pruning cut may be required to encourage growth bilaterally along the wire. The pruning cut should be made through the node that is ABOVE the nodes that will grow along the wire. This will prevent damaging the node with the wire, but will allow the shoot to be secured to the wire. The emerging lateral shoots should be tied and trained along the wire in each direction. In some cases, no pruning cuts are needed and lateral shoots have already developed the correct placement (Figures 3A, 3B).
Figure 3A. Examples of training cordons at the top wire in season two. Bilateral training attaching the cane to the bamboo 6 inches below the top wire, and 6 inches away from the bamboo onto the top wire.
Figure 3B. The shoot is tied along the top wire leaving enough room for internode expansion and continued growth. Lateral growth along the trunk is retained in season 2 but will be removed during the winter before season 3.
An alternative is to train unilaterally in season two and establish the opposite cordon in the following year (Figures 4A,4B). Double trunk vines could be trained to the wire and then in opposing directions. Lateral shoots will become the canes that produce the first fruit crop in year three. If clusters are observed in year two, they should be removed. Pruning cuts that remove the apical growing point disrupts the hormones in the plant and removes “apical dominance” allowing the other buds to swell and develop. These lateral shoots may also develop lower along the trunk and these should also be trained to a trellis wire or maintained through the season to collect the sun’s energy.
Figure 4A. Examples of training cordons at the top wire in season two. The established trunk before training the shoot .
Figure 4B. The established trunk after training the shoot unilaterally. In season three, two new laterals may be trained bilaterally along the top wire (see figure 3) or the tied shoot retained and a second shoot trained to balance the vines growth in opposite directions.
Bull canes, which are very thick, rapidly growing canes with long internodes (the space between nodes) are not desirable for the trunk, cordons, or heads. Some varieties are more likely to produce bull canes and management practices can be used to redirect growth to reduce the vines overall vigor. Bull canes are more susceptible to winter injury, have longer internodes, which means less fruit per unit area, and often produce less fruit.
Pruning the dormant vines before season three will establish the cordons or canes and select the nodes that will produce the fruit for the coming season.
Prune before season three to maximize fruit potential and to continue to establish the plant architecture of the desired trellis and training system.
If only one arm was established in year two, the opposite arm should be trained in season three (Figures 5A, 5B).
Figure 5A. Example of vertical shoot position trained vines (VSP) in year 3. Notice unilateral training (to the right) conducted in year two and one shoot remaining to be tied into place for the left cordon.
Figure 5B. Mature VSP vine exhibiting balanced growth with cordons trained in 2 separate years.
In year three (and possibly before) the grower may notice new shoots developing at the base of the trunk or from underground. These “suckers” should be removed, as well as any other lateral growth that is not desired along the trunk. These shoots are undesirable as they take important nutrients and water away from the portions of the vine intended for production.
Vines that are prone to bull canes should be managed so that excessive growth be redirected into the canes but not in the fruiting zone. Bull canes can also be removed midseason which allows for the vine to gain some of the benefits of being de-vigorated by having the bull cane during active growth to take some of the energy.
Grapes bear fruit on one-year-old wood. This means that in season three, all of the flower initials are being formed in the nodes that will be dormant in the winter and grow in year four. Pruning, which removes 80-90% of the growth between seasons three and four, must take into consideration the selection of canes or spurs that will produce the new crop.
Figure 6A. Winter injury has caused these vines to die to the ground. Notice the well trained cordons that had been established in season two.
Figure 6B.Multiple trunks are retained to help de-vigorate the vine in both examples.