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Pruning 101

January 27, 2016

Photos:

A Head Trained, Spur-Pruned “Old Vine”
Old Vine Vineyard
Bilateral Cordon Spur-Pruned Vine
Cane Pruned Vine
Unilateral Cordon (Spur Pruned) Before Cane Conversion
Unilateral Cordon After Cane Conversion

It’s that time of year again where we dust off the old pruning shears and head out into the vineyards to do a little cleaning up. Pruning is arguably one of the most important and costly tasks in the vineyard. It’s such a big deal that annual pruning competitions are held in order to praise the art of neat and skillful pruning, so it might help to first get familiar with some terms. Pruning itself is simply defined as the removal of the previous year’s shoots and canes. Winter buds (found at the nodes of grapevine shoots) are what you leave in order to produce this year’s crop. The buds will either be left on a cane or spur (known as the fruiting units) depending on the style of pruning you choose. Ultimately, the number of buds left on the vine (depending on fruitfulness) will determine potential crop. Now throw in different pruning systems and it gets a little more complicated especially when you factor in desired outcome in terms of yield, quality, and vine management.

The three different systems we use here at Rodney Strong are head trained, cordon spur pruned, and cane pruned. Cane pruning requires the annual replacement of the long fruiting units known as canes (usually 1-2 feet long with around 8-12 buds). So essentially you cut back last year’s canes (two years old by now) and replace them with newer, one-year old canes which will be this year’s fruit bearers. Cane pruned vines are usually head trained, meaning the fruiting units arise from the central part of the vine. Depending on the desired outcome in terms of vine capacity and yield, growers will usually leave 1 to 4 canes per vine. Leaving more canes increases the number of buds left on the vine which in turn increases the potential crop. But really it’s all about vine balance, as a balanced vine produces top quality fruit. Seems simple enough, right? Well not so fast… the thing about cane pruning is that it requires a certain amount of skill in choosing the correct canes to keep as the health and vigor of these chosen canes will, to some extent, determine the quality and quantity of your crop.

Cordon pruning (aka spur pruning) is different from cane pruning in the sense that the fruiting units—known as spurs for their short length—are located along the cordon (which is a permanent horizontal arm of the vine). The spurs are essentially one year old canes that are cut back (usually to about 1-2 buds per spur). Again the number of buds per spur and spurs per vine determines yield and canopy growth. For both cane pruning and spur pruning, the desired outcome is always vine balance and fruit quality. Leaving too little buds or too many can be detrimental in terms of excessive vigor and shading or insufficient canopy unable to ripen a heavy crop, respectively.

Last but not least are head trained, spur pruned vines. Head trained (or bush vines) are grown without the support of wires and stake so the result is a short, thick vine with permanent short-branched arms forming a goblet shape. The careful selection of spurs in the winter helps to maintain the shape. This system is one of the oldest in place and head trained vines are usually referred to as ‘old vines’ since most head trained vineyards are decades old and look pretty gnarly.

As with everything, there are pros and cons to each system. To name a few, cane pruning can be much more time consuming and costly than spur pruning as it requires a higher level of skill than spur pruning and therefore takes more time (i.e. money) to do. However, cane pruning has a distinct advantage over spur pruning in terms of controlling grapevine trunk diseases such as Eutypa. Trunk disease is caused by a fungi that infects the woody tissue of vines and causes abnormal shoot growth, severe reduction in yield, and eventual death of the vine. The fungi is easily spread via rainfall during winter pruning where pruning cuts serve as infection sights. With cane pruning there are fewer large cuts made and therefore less room for infection. Furthermore, most trunk disease infections are found in the upper portion of the permanent wood so the renewal of canes every year would theoretically remove any infected wood without hindering quality and crop yield. That being said, vine balance is still the most important consideration when choosing pruning levels and systems. A healthy, balanced vine is able to produce and ripen a quality crop within an optimal timeframe as well as retain a good balance between vegetative growth and fruit production. Due to the fact that cane pruning allows more buds to be retained on the vine, many people believe that cane pruning enhances vine capacity and is the best option for vigorous vineyard sights. It kind of seems counterintuitive to control vigor by leaving more buds, but the reasoning behind this is that a vigorous vine is able to support more growth especially during early shoot growth. Restricting vine capacity by leaving too little buds can result in excessive vegetative growth and a reduction in yield as the vine will focus all of its energy and nutrients on vegetative production.

Spur pruning, on the other hand, has many benefits as well. For one, spur pruning can allow for greater uniformity along the vine as well as limit fruit production to specific locations along the cordon. For smaller vines on less vigorous sights, limiting the amount of buds retained on the vine allows for a smaller crop that the vine can then ripen. It also makes canopy management a lot easier. However, spur pruning can severely limit yield on varietals that have more fruitful buds farther along the cane (this is known as apical dominance). Lastly, head trained vines that are spur pruned require little manipulation and are usually very well balanced, producing some beautiful fruit. However, because there is no real training and trellising system it is hard to manipulate production past retaining a certain amount of buds on the vine. Therefore productivity tends to be lower than their counterparts. Shoot crowding can also be a problem and if left alone can cause over shading and high disease pressure.

By now you may have gotten the gist that vine balance is key to producing high quality fruit and maintaining a healthy, long-lasting vineyard. Choosing the right pruning system is one way to help manage vine balance. Because no two vineyard sights are exactly alike, here at Rodney Strong we consider all factors that go into producing a high quality crop—from climate to soil fertility—when determining the best pruning method. We also use a strategy called the balanced pruning method in order to further inform our decisions. Balanced pruning uses specific metrics such as the weight of last year’s canes (collected during the dormancy period from a representative vine) to determine the vegetative vigor of a specific block. If a vineyard is out of balance, it may be necessary to convert from cordon to cane pruning. As mentioned above, the benefits include optimal vine balance, increased fruit quality, and preservation of vine health. By evaluating all factors that go into a big management decision such as pruning, we are able to achieve greater vine balance as well as farm more sustainably. A balanced vine is a happy vine requiring less inputs.