As we begin this wet, cool 2017 growing season, shoot growth appears to be in slow motion. With heat predicted next week we will no doubt see a rapid jump in shoot length. I am struck, nonetheless, by the challenges of inducing early water deficit in such a wet spring. The goals of depleting excess soil water and frost protection are going to be at odds, but all we can do as viticulturists is make conscious decisions to try to maximize both of these contradictory goals simultaneously.
The levers we have to pull to accomplish this are floor management and suckering and, to a lesser degree, irrigation and fertigation. It certainly seems like a year to hold off on cultivation in all but the driest, low vigor sites. High mowing would be ideal, but may not give the air flow necessary for frost protection. It also could be a year to leave the trunk suckers on late to help deplete soil moisture. I believe we will also need to be cautious about possible root pruning due to high water tables in low spots. Careful monitoring of shoot length elongation rates will help avoid surprises in that regard. They can also be useful in deciding when to turn under those cover crops. This simple tool can be extremely useful in this early part of the season where the lack of fully developed shoots makes other plant based measurements like sap flow, stem water potential and porometer readings impossible.
The trick this year is going to be to get the vines to shift from the vegetative to the reproductive cycles and to avoid high early pyrazine levels that we will then fight for the rest of the season.
The other risk with a cool, wet spring is that bloom will be heterogeneous due temperatures being less than ideal for set. The next few weeks will tell that tale.
It’s always something. That’s why it’s called fishing and not catching.
Daniel Baron is a viticulture and winemaking consultant based in Napa, California. He began his career in the early 1970’s as a field worker in the vineyards of Knight’s Valley, became one of Dr Harold Olmo’s last graduate students at UC Davis and one of only 6 people to intern at Chateau Petrus, his being the only one-year internship. He was General Manager of Dominus Estate for 12 years and Director of Winemaking at Silver Oak and Twomey Cellars for 22 years. He utilizes an integrated approach that combines precision farming, collaborative leadership, science-based winemaking and old-world artisanal techniques to produce vibrant, moderate alcohol wines.
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