The Cadenza Bud-Count Pruning System

 

Every year we prune our grapevines during the dormant season.  Every year. And by dormant, I mean winter.  It's part of the rhythm of a vineyard, and it's the most important task that we do. It sets us up for the growing season by delineating the exact amount of growth that we expect the vine to have.

Vineyards are rarely uniform.  When we plant a vineyard, for the first few years everything looks perfect.  The rows are all perfectly straight, and the vines consistent from end to end.  What's hidden at this time is the variability of the soils in which the vines are growing.  Each little bit of earth around each vine is slightly different from its neighbor's plot.  Perhaps a little more clay, or less iron, or more rocks.  Or even a little higher or lower, thereby affecting the amount of water that flows past it during the year.  And even a little different bit of sunlight throughout the day depending on any aspect change.

After a few years for those of us growing vines on the East coast, we'll perhaps notice some holes in the vine rows.  Vine death is the most important impediment to the long term health of a vineyard.  Vines die due to freeze events, trunk diseases, and a host of other reasons (including tractor blight.)  It may not happen to all vineyards, but it happens to most.  By year ten or twenty, a vineyard isn't looking nearly as uniform and perfect as it did when first planted.

When growing fruit in this environment, it's important to understand the healthiest vines are the ones that are in balance.  The variety (clone and rootstock) matches the soil and climate, and the trellis design strikes the right balance between the vine and its environment.  This is the permanent structure that will remain mostly unchanged throughout the life of the vineyard.  On an annual basis, though, the grapegrower has the opportunity to help the vine achieve its ideal balance through the winter pruning process.

We use a training system called VSP which stands for "Vertical Shoot Positioning."  It's kind of self-explanatory, but we're basically putting a new cane from the vine on a fruiting wire every year.  During the growing season, that cane produces shoots (canes) from its buds which we then position vertically in the trellis creating a canopy that resembles a solar panel. The real question that determines the health of the vine and the quality of the fruit in the upcoming year is: how many buds to leave for the vine?

Years ago, there was lots of research done whereby one could weigh the prunings of a vine and determine how many buds to leave.  This meant that the person pruning would have to tie up all the pruned canes and weigh them on a scale and then do some calculations to come up with how many buds to leave.  After doing this for about three vines, most give up and guess on an average number and prune the rest of the vineyard to that uniform bud count.

The problem becomes a practical one.  How does one efficiently address the variability in each vine across an entire vineyard while at the same time making it so that the work is as efficient as possible?  

I once spent a day with Lucie Morton, and she in passing made a comment about vine vigor.  She said that you can pretty accurately estimate how many canes a given vine is going to push in the following growing season by counting how many pushed in the past one.  This sounds like such a basic idea, but it is as close to a golden rule as I've ever found in a vineyard.  (Of course, there is vintage variable as well as health and pest influences that can't be accounted for in this idea, but the kernel is pretty accurate.)  I took this idea and tried to form a system out of it.

The Cadenza Bud-Count Pruning System is pretty straight-forward.  I'll outline it in a few steps.

• When you go to prune a vine, count how many good canes are on the vine.  That's number signifies how many buds to leave on the vine.
  
• A good cane is one that reaches the optimal length for your trellis system.  For VSP, I consider that a vine that hits the top wire and was hedged once.
• If there's a bull cane (larger than the diameter of a marker), it counts as two canes.
• A cane that only reaches halfway counts as a half cane.

There are some other key factors to think about, and here's what I've found as we prune our double-trunked double Guyot VSP vinifera vineyard (planted 1 meter between vines and a 34" high fruiting wire).

• I try to leave double the bud count on the entire vine, as we treat early season shoot-thinning as the final "pruning" of the season.   We cut the canes to length and staple them to the fruiting wire.  This is basically like leaving a sticky note on the vine that explains how vigorous the vine was in the previous season.
• When we go to shoot thin, all you have to do is count one cane to find how many buds the vine was supposed to have, and then thin the vine accordingly.  This practice also allows for insurance buds that might have been damaged due to freeze events or frost.  
• I do not count one-bud spurs left for renewals for the next pruning season as part of the bud count of the vine.  If your vines are very well-balanced, you may need to count those buds
• We do this method across each block.  If I find that the vines are a little vigorous on the whole, I might add a base number (such as two extra buds) to each vine.  I try to do this block by block as it makes determining the number of shoots to thin to easy to determine. 
• If you end up *not* doubling the bud count (for vines that have long internodal distances and where the canes would otherwise overlap), just be aware that you don't have any insurance buds.  This is where I usually add a base number (say two extra) to the bud count.

It's easy to tell when a vine is in balance by the size of the canes and the distance between the nodes.  A vine that has lots of shorter canes or has shorter internodal distances is most likely suffering from having too may buds left on at pruning.  A vine with lots of bull canes and larger internodal distances has had too few buds left.)  

If this system doesn't work for you, it's probably because something is mis-matched in your vineyard.  In other words, the three components of your vineyard are somehow out of balance (site/trellis/vine), and you may need to consider some sort of remediation.