We are off to an early start with the 2015 Napa Valley Cabernet Sauvignon vintage—here on Diamond Mountain our vines budded out about 10 days ahead of normal. We did something a little different this year with our pruning, which you can see in this photo. Mid-winter when the vines were very dormant we pruned the long canes from last season, and pulled them out of the trellis wires, a very slow process. But instead of leaving two buds per spur on our cordon arms, we left four (as in the front row in the photo). Then last weekend in one day we went back through the vineyard, and quickly cut off the other two (as in the row in the background). This of course requires an extra pass through the vineyard—why would we go to this extra work (referred to as double pruning)?
There are two reasons. The first has to do with frost avoidance. Though we are in the mountains which are less susceptible to frost, which commonly forms on the valley floor where the cold air settles, our site is on a bench next to Diamond Mountain Creek, and once in a while frost does affect the lowest portion of the vineyard—in 2008 we got hammered with enough damage to the young buds that our crop was about half of normal. Because the uppermost buds on grapevines break first (this is called “apical dominance”) the lower two buds will be a little slower to push. This delay increases the odds the nights will be a little warmer when they finally do push. The other reason is the pruning cut can be infected by a grape disease called eutypa—it has the nickname “dead-arm” which is descriptive of what it does. A preventative measure is to paint every cut with as sealant, which is laborious. By making the final cut just as the vines are waking up, there will be fewer spores present under the drier conditions, and the sap will flow out of the cut, making its own seal as in dries up. This “bleeding” is not harmful to the vines.As double pruning goes very quickly, we can wait until the leaves are pushing on the upper buds that have yet to be removed. The canes from both the early and late pruning (long and short) are dropped between the rows, to be chopped and cultivated, adding organic matter to the soil.
Please check back to follow the twists and turns of the 2015 season.