Harvest is done, the wines are maturing and there is not much to do at the winery at the moment, WRONG.
But what is pruning and how do we go about it?
Pruning establishes how many buds remain on the vine, buds in turn create shoots on which clusters are carried. It therefore stands to reason that the greater the number of buds, the greater the potential yield. Sounds easy doesn’t it? There is more to this scenario than just meets the eye.
How many buds do you leave, what is the correct tonnage for your particular block of grapes? Well, that is dependent on the age of the vineyard, the soils on which they are planted, the density of the vines, the elevation of the vineyard as well as the direction in which the rows are planted. We can save this for further posts down the road, so let’s just stick to pruning for the time being.
Proper pruning creates a balance between the number of clusters and the vines leaf area. If not done correctly, your vineyard may be either over or under cropped, both of which negatively affect the quality of your fruit and thus the wine. Too much fruit, and the vine will not be able to properly ripen the fruit, too little fruit might lead to overly vegetative conditions, creating problems with shading.
At Keswick our vines are planted at a width of 9 feet with a spacing of 6 feet, meaning that we have 806 vines per acre planted. So how do we work out how many buds to leave?
By using the following formula
PY = (ANV x NC x CW) / 2000
PY = Predicted yield in tons per acre
ANV = Actual number of vines per acre
NC = Number of clusters
CW = Cluster weight
So if we pruned to 40 clusters per vine with a cluster weight of 0.23 lbs we would have 3.7 tons per acre using the formula above.
This is an ideal target, but at the moment we are pruning slightly higher than that to ensure we have enough buds on the vine in case we lose some due to spring frost and various other factors. During the course of the growing season, we will then move through the vineyard and get the tonnage per acre to exactly where we want it.
What we are trying to achieve is the correct balance between quality and volume, ensuring the vineyard is able to produce fruit that will enable us to craft the best wines possible.
Kind of cool to think that what we do today, has a direct impact on harvest due to start in 6 months time.