Are You Happy with Your Vineyard Training System?
When I mention canopy management in public, people often ask me when I will update my book “Sunlight into Wine”. Recently I have given this idea some more thought. Maybe the presentation could be improved, and some contributors’ comments updated, but the basic principles are unaltered and are still valid. There is not much new in the design nor management of the trellis systems. So, to date, I have not bothered.
In this column, I would like to offer some thought about the application of grapevine training system to Midwest viticulture. Much of what I say here will be a direct follow on from my first three columns in this magazine, which dealt with vine balance and trunk diseases. I should acknowledge here that Mike White, extension specialist at Iowa State has been particularly helpful in providing me with information about current developments in the local industry especially in relation to grapevine training systems.
What is the Preferred
Training System in the Midwest?
Mike White has produced a so-called “cheat sheet” in 2014 for pruning and canopy management. Many of the metrics and the guidelines are borrowed from Sunlight into Wine. For the 47 cultivars reviewed the preferred training system was a single high wire (SHW) at 62%, the second at 33% was Geneva double curtain (GDC) and the third vertical shoot positioning (VSP) at 24%. Mike’s estimate for training system use in the Upper Midwest is approximately 60% SHW, 30% VSP, 7% GDC and 3% other.
I have been impressed with the output of the Northern Grapes Project which is freely available on the web. Mike states that this project has encouraged the single high wire training system for reasons of lower labor input and ease of hand harvest. Vertical shoot positioning gives lower yield and higher hand labor costs, especially for canopy management.
I am aware that the varieties of the upper Midwest are different from most places in the world, involving hybrids with Native American species and or some French vinifera. These hybrids are classified in Mike’s cheat sheet as vigorous or moderate to vigorous (62%) and of trailing or semi-trailing growth habit (70%). As to pruning, I gather this is mostly to spurs sometimes longer than the normal.
In preparing this article I have reviewed the book “Growing Grapes in Minnesota” and also the research work presented on training for the Northern Grapes Project. I saw that the book chapter requires some revision as some of the systems mentioned no longer have relevance.
What do you look for in a training system?
I understand that around 70% of vineyards in the upper Midwest are small, around 2 to 4 acres, and are run on a part-time basis. This necessitates limited machinery investment and emphasis on laboursaving. For most of the rest of the world, the emphasis is on vineyard yield and associated economics, also wine quality. No doubt this will change for the Midwest as the industry evolves, with some growers becoming larger, and others deciding that grape growing on small acreage has limited financial and personal rewards. I sympathise with growers having to prune in the snow; I had my fill of that during PhD studies at Cornell.
I will now make comments on various training systems from my experience.
Single High Wire (SHW)
This system was popularised by the Italian scientist Dr Cesare Intrieri in the 1980s. He had been impressed by the Geneva Double Curtain developed by Shaulis of NY, using the concept of downward training of shoots from an upper cordon which gave benefits for both mechanical harvesting and mechanical pruning. Downward shoot positioning was an essential part of the process, as was maintaining a relatively open canopy. Training to a high cordon is now becoming very popular in California, encouraged by the need to mechanise pruning due to labor shortage.
This system is suited to cultivars with a trailing growth habit but not vines of high vigor, otherwise there are difficulties in combing the canopy and it easily becomes too dense and shaded, despite the fruit being at the top of the canopy. Such vines are better suited to the GDC.
There is little you can do to improve the situation of the unsatisfactory canopy on the SHW. Making cordons much longer will help to reduce vigour, but will encourage susceptibility to winter kill and trunk disease. My suggestion also would be to use two trunks rather than one.
Geneva Double Curtain (GDC)
This system should become the most widely used in the upper Midwest. It is simple and cheap to construct, and easy to manage for hand harvest. Please note that the diagram on page 67 of the Minnesota handbook is incorrect. This mistake can be traced back to Shaulis. He liked individual vines trained to one side of the GDC or the other to make the measurement of pruning weights easier. However, this diagram has caused confusion to growers ever since. Please refer to the GDC description in Sunlight into Wine. It is preferable to train the one vine to both sides of the GDC, and to keep the arms connecting to the cordon horizontal, to facilitate mechanical pruning.
I suggest pruning using finger and thumb with downward pointing spurs only. Do early bud rub of any upward pointing shoots. You will also find that the swinging shoot positioning arm as shown in Sunlight into Wine facilitates downward shoot positioning. The timing of shoot positioning is critical as for most things in grape growing. Do the shoot positioning at the beginning of flowering, before tendrils begin to bind the canopy. The downward orientation of shoot growth reduces vigor, as does the better yield of the GDC. Remember that a canopy with 5 shoots per foot is normally about optimal density.
Do not give up on the GDC, nor let anyone tell you it is difficult to manage. Persevere with it and learn all the management tricks and it will reward you well. It is not difficult to shoot position the GDC when properly pruned and if operations are done at the right time. It is the system best suited to the majority of upper Midwest vineyards.
Vertical Shoot Positioning (VSP)
This system is widely used around the world for vinifera vines, but is poorly suited to high vigor vines with trailing growth habit. Various experiments in the Upper Midwest have shown this opinion to be valid, with low yields associated with shading, and high costs of shoot positioning (canopy management). The VSP system is best suited to combinations of more erect shoot growth and lower vigour.
Scott Henry/ Smart Dyson
Both of these systems will be a marked improvement over VSP in terms of yield, reduced disease pressure and improved wine quality. They have vertical canopy division, with a canopy of upward trained shoots above a canopy of shoots trained downwards. The Scott Henry is cane pruned and the Smart Dyson spur pruned, which may make the latter more amenable to the Midwest. There are upwards and downwards facing spurs on the same cordon. This is easy to develop, just do not cut off the downwards facing spurs as is normally done.
Canopy density is less than for VSP, as it is spread over two curtains and not one. Fruit exposure is better, and hand and mechanical harvest are facilitated. However, I hear reports about the complexity of the Scott Henry. It is new, but not complex nor intellectually challenging. As for GDC, timing of shoot positioning is everything. Early in bloom begin tucking upwards shoots between the first set of foliage wires; and sweep the shoots downwards pointing behind the training wire. This is moved downwards around the end of flowering, moving the shoots to now face downwards. Complete any necessary herbicide spraying before turning shoots down.
Shoot positioning for the Smart Dyson is similar, and again timing is critical. So is trimming of upwards pointing shoots, the first trim should be well before veraison, and if vigor is controlled there may be need for only one more trim. Ditto for the Scott Henry.
Studies in Iowa and Wisconsin have shown the yield benefits of Scott Henry training system, but much higher shoot positioning labor. I believe this could be reduced by better management following the guidelines given here and in “Sunlight into Wine”.
Human Nature and Change
I want to make a final point about human nature, and change. Most of us are reluctant to make changes in our lives, be they personal or professional or even how we train grapevines. Change means stepping outside our comfort zone. I know from personal experience that I might introduce growers to new systems, that will make their vineyards more efficient and profitable, yet the questions they ask are always doubting the benefits I quote. Why, because they are thinking of ways to rationalise to themselves why they don’t have to change from their present method.
Let me give an example of how I and others were able to overcome this psychological block. Around 2010 I was consulting with a client in New Zealand, Delegats Wine Company, a large and progressive company; I was trying to convice the vineyard managers that VSP training was unsuitable for many of their vigorous Sauvignon Blanc vineyards (and other varieties), because of loss of yield and quality, and more disease susceptibility etc. So the managers started to tell me all the reasons why Scott Henry would not work, mostly fabrications and imagined scenarios, to justify them not having to change.
The National Vineyard Manager was with us, and said to the managers “Don’t tell Richard he is wrong. Show him he is wrong.” So, they did trials of decent size, and presto, demonstrated I was right. The winemakers were thrilled with the results, and also the managers, and the boss was particularly happy! Now, around 8 years later, there are 5, 800 acres of Scott Henry, and no VSP remaining on the company’s vineyards in New Zealand and Australia; several hundred new acres of Scott Henry are added each year.
There is no reason why the same benefits might not be achieved for some varieties in the Upper Midwest! Remember, most obstacles to adoption are psychological!
My experience suggests that Geneva Double Curtain training will be best suited to the majority of vineyard sites in the Upper Midwest, considering vigor and growth habit. There seems to me to be no reason to persevere with Vertical shoot positioning, it will be unsuited to most situations. Vertically divided canopies like Scott Henry and Smart Dyson seem better suited than VSP.
For all trellis systems there are probably tips to be learned from elsewhere to reduce labor requirements. Shoot positioning times for Scott Henry and Smart Dyson can be done for about 15 hours per acre, involving 3 or so passes. Let this be the standard to aim for in the Upper Midwest.