Cold Tender Cultivars
Training Systems for New York Vineyards
© Copyright 2000 Robert Pool
The goal of this article is to discuss factors you should consider when choosing a training system and briefly discuss them in relation to varieties and growing conditions found in New York. But first we need to make clear the distinction between pruning and training.
Dormant pruning has the following basic objectives:
Training involves the placement of the retained canes and growing shoots so as to shape the vine. The vine shape in turn will influence the extent to which:
Although, by tradition, we in New York refer to training systems by name, they can also be more logically classified into four major groups.
Additional, informal classifications for training systems include the nature of the renewal zone (that area where the buds which will produce next year's crop are formed), the extent of permanent wood (trunks and cordons), the type of bearing unit, the height, and the extent of canopy division.
The renewal zone may be diffuse (6-Arm Kniffen) or discrete (Mid-wire cordon). It may be at the top of the canopy (High Wire Cordon), or at the bottom (Pendlebogen).The location of the renewal zone in a given training system affects the extent to which shading influences development of retained buds. Buds that develop in shaded renewal zones are reduced in fruitfulness, and because fruit is usually located at the same place, fruit is also often shaded as well.
The amount and nature of the permanent wood (trunks and cordons) affects both cost and fruiting potential. Cordons are horizontal trunks (High Wire Cordon). They cost more to establish, but are more permanent (except with cold tender varieties), and can make the job of pruning more simple to visualize. They also offer more space to distribute bearing units, and so can reduce canopy crowding. With cordons, the vine canopy in the row becomes continuous, helping to reduce canopy gaps and increase light interception. When cordons are not used, the bearing units arise from one or more discrete heads (Umbrella Kniffin, 6-Arm Kniffin, Guyot). Usually head training requires very close vine spacing or the use of long canes to ensure reasonable canopy leaf fill.
The bearing units are either spurs or canes. A spur is a short (less than 4 node) cane. Canes (>4 nodes) and head training are often used in cooler climates, because they allow the space between vines to be filled with shoots. With most training systems cane pruning is more expensive, because the canes must be tied into place. However, with varieties with a procumbent (drooping) growth habit and a high renewal zone, hanging canes that do not require tying can be used. With large vines, it is often difficult for light to penetrate to the basal nodes of the shoots that will be used for canes or spurs the next year. In many cases this results in wood which is not suitable for spur pruning. However, because the nodes farther out on the same shoots get more light, they will form productive canes. Thus cane pruning has been used as a way to combat shade effects.
Renewal zone and trellis height are both important (Figure 3). Wide row spacing requires tall canopies to ensure reasonable light interception. Practical considerations restrict canopies to about 6-7 feet high. Trellis height cannot be any greater than row width, or shading of the canopy occurs. Row width can be greater than trellis height, however in that case light interception is not optimized. The minimum row width needs to be based on equipment size. When vine growth is very vigorous, or when rows are widely spaced, canopy shading can be a problem. One way to reduce canopy density and to increase light interception is to use a divided canopy (GDC, Lyre, Scott Henry). Horizontally-divided canopies (GDC, Lyre) mimic the canopy distribution obtained with narrow rows, but allow machine access provided by wide trunk spacing. It is generally difficult to convert a vineyard from a single canopy system to a hortizontally-divided system (GDC, Lyre) due to the resulting reduced row width that interferes with equipment. In that case, a vertically-divided system (Scott Henry) can be used. Divided canopies are more expensive to install, but the increased yield or fruit quality (from improved light interception by buds and clusters) can compensate for the increased cost. Divided canopies require vigorous vines to fill the trellis, but they also provide a solution when standard training results in excessive vigor and canopy density.
Choosing a Training System
Some site factors to consider when choosing a training system include soil, temperature and status of vines. Soil depth, texture and drainage will all influence vine size. The summer temperature as well as potential cold injury in the winter also needs to be considered when selecting a training system. And finally the replant status of the vines needs to be considered. Were there vines in the proposed vineyard last year or was there a fallow period? This will also affect vine size.
Cultivar is the most important factor to consider when thinking about a training system. Essentially we grow three kinds of wine grapes in New York: Native American, hybrids and vinifera. Each class has very important characteristics which influence training system choice. Native American varieties have procumbent (drooping) growth habits which dictate a high renewal zone. Their bud development is very sensitive to shade, so there is a need for an extensive, diffuse canopy system such as obtained with High Wire Cordon. With conventional pruning, special treatment such as shoot positioning may be required to obtain sufficient illumination of the renewal zone.
Many hybrid cultivars have very fruitful buds and a tendency to produce fruit from base buds (which arise at the base of a cane). Their growth habit is variable, but shoot growth is usually more erect than with the Native American varieties.
Vinifera varieties tend to have upright to very erect growth habits. As a class they are winter tender which makes it difficult to produce long-lived trunks. As a result cordon training is generally not suitable except where cold injury is rare (such as Long Island).
Cultivar considerations in choosing a training system:
Varieties with erect growth habits lend themselves to systems with lower renewal zones such as mid-wire cordon or pendlebogen. Varieties with procumbent habits should have a high renewal zone to improve the light environment in the renewal and fruiting zone.
Crop control is easier with cultivars that have fruitful base buds when there are fewer sites for base bud retention. Cordons have many sites where base buds are retained, and these greatly increase the number of clusters produced at a given pruning level. In one study, we found that 60% of the crop of DeChaunac originated from base buds. Head/cane training systems will reduce crop potential from base buds.
Another factor to consider is cluster weight. Traditional spur pruning generally retains fewer nodes per vine than cane pruning. Thus spur pruning is useful for varieties with high crop weight production per retained node, and cane pruning is used for varieties with small cluster weight.
Fruit and the buds in the renewal zone tend to be produced in the same place. Shaded renewal zones also affect the microclimate of the fruit zone. Dense canopies restrict air flow, increase drying time and interfere with spray penetration. For varieties that are sensitive to bunch rot, such conditions can spell disaster. This is the reason that Riesling does well when Pendlebogen trained. When Pendlebogen-trained vines are vertically shoot positioned, their fruiting zones can become very well ventilated, substantially reducing fruit infection. Cheaper alternatives such as Umbrella Kniffin are compromises where fruit crowding is avoided by distributing the clusters widely over the trellis, and are suitable for moderately valued fruit.
Vine and row spacing will affect vine size and thus affect training system choice. Closer row spacing can decrease individual vine size by reducing root volume per vine. Vine canopy density tends to be decreased as in-row vine spacing increases. However, very wide in-row spacing will dictate a cordon training system in order to ensure the space between canopies is filled with leaves.
Economic considerations with respect to labor inputs are important when choosing a training system. Divided canopies generally require more hardware than non-divided canopies and therefore increase the cost of installation at planting. Additionally, labor costs associated with training choice need to be considered. While some low-vigor hybrids may do well on a VSP system, labor costs for shoot positioning and leaf removal may not be feasible due to the lower value per ton of hybrid fruit.
The value of the crop will dictate how many inputs the grower can afford to put into their vineyard. Economic pressures are leading more and more people to adopt machine pruning. Machine pruning systems are best adapted to cordon training which tends to enhance canopy uniformity along the row. Mid-wire cordons work well with close hedging of fruitful varieties, and top wire cordons are more useful for Native American varieties.
Ultimately the training system must be matched to the vine vigor. Training system will have little impact on the open canopy found with low vigor vines. However, these vines will also be low yielding. Most often the goal is intermediate vigor, but as vigor increases training system will have a greater and greater impact on canopy density, yield and quality. Very high vigor vines may require canopy division to prevent excessive canopy density.
The primary strategy for growing cold tender grape cultivars in New York is the use of spare parts so that cold damage can be tolerated. Because both trunks and buds can be winter-injured, the attempt is to provide an excess of both, and adjust the final crop only after spring growth signals winter survival. Thus training systems that are costly to establish, such as high wire cordons and GDC, should be avoided for cold tender cultivars. It is easier to distribute and rapidly adjust the crop when many short trunks are utilized and when cane pruning is done. Thus the majority of cold tender grapes are produced on a low head, cane pruned system such as Flat cane VSP (i.e., Guyot) or Pendlebogen. These systems requires intense management, and the alternative, Umbrella Kniffin is often more suitable for lower value fruit.
The winter of 1993/94 was one of the coldest on record in the Finger Lakes. Temperatures in our experimental plantings reached -16°F on more than one occasion in January, 1994. Table 1 shows winter survival of young Chardonnay vines trained to 7 different systems. Lowest bud kill was associated with highly managed systems, but maximum return yield was from Lyre training. It appears the high yield was not only due to well matured, winter hardy canes, but also to the very large number of buds available to survive the winter. The low cost Mid-wire cordon system produced quite substantial yields, but we had to replace all of the cordons over the next few growing seasons.
There are a wide variety of training systems appropriate for the myriad of cultivars, sites, and production goals that exist within the NYS grape industry. Repeatedly, research has demonstrated that the appropriate choice in training system can result in high yields with good fruit quality, however this can only be achieved when all vine conditions and management goals are factored into the choice of training system.
Reynolds, A.G. and J.E. Vanden Heuvel. 2009. Influence of grapevine training systems on vine growth and fruit composition: A review. Amer. J. Enol. Vitic. 60(3): 251-268.
© Cornell University, Department of Horticulture.