Baby, it’s cold outside: When your vineyard catches a cold

In this May 2019, vineyards covering thousands of aces across California found themselves at the mercy of mother nature once again, leaving the fate of the 2019 vintage in limbo. An extreme, nonseasonal weather pattern ripped through the West Coast just as many vines had begun to bloom, entering some of the most sensitive weeks of their annual growing cycle.  

Bloom timing and duration vary season to season 

There are several elements that impact bloom timing and duration regionally every season, including rainfall, temperature, radiation, and elevation. Different grape varieties stagger their bloom over the course of the late spring, some shooting out their anthers and stigmas in early May, and others in June. North Coast early cultivars in both 2011 and 2018, bloomed unusually late, well into the last week of June, as opposed to vintages 2013-15 that primarily bloomed in the first half of May.  

The timing of bloom is critical, especially in vintages with extreme weather events in late spring. A storm or cold front could cause shatter, resulting in reduced yields in some varieties, while leaving those with more gradual phonological development unaffected. Because of this annual variance, proper tracking of block-level phenological development is crucial in evaluating the impact of different weather events on yields.  

Two-week delay in budbreak 

The 2019 season kicked off with temperatures 3°F cooler than average for early spring which influenced a two-week delay in budbreak across California. This lag in development shifted the vulnerable window of bloom for many varieties to be later than usual as well.   

In an unfortunate combination of unseasonably cold temperatures for May along with rain, strong winds and even hail, some early blooming varieties that carpet Northern California, like Chardonnay and Pinot Noir, found themselves grasping on to their freshly opened flowers for dear life. 

20°F below may average  

In Sonoma County, daytime temperatures dropped 20°F below the historical average and 10°F lower than 2010, which previously held the title for the year with the coldest May temperatures since the turn of the millennium. Both high and low temperatures crept worryingly close to the historical lows set decades ago. These extended irregular temperatures were served with a garnish of 22 MPH winds and four inches of rain, at times morphing into hail. This unfortunate “perfect storm” of phenological development timing and a unique brew of weather elements has historically led to decreased yields of nearly 20% in previous vintages.  

Similar May conditions led to 20% yield decrease for early varieties   

With conditions forecasted to dry up and temperatures on the rise again, these vines will begin fruit set in the coming weeks, and cases of shatter will become visually apparent and quantifiable in the vineyard. Only then will growers, vineyard management companies, traders and wineries begin the enormous task of evaluating the damage. With harvest less than three months away, these estimates will ultimately dictate some of the most crucial business and farming decisions that will shape many companies’ profitability for the 2019 vintage.  Stakeholders that can quantify and act on these projections earlier with more confidence will operate with a significant advantage in the market. 

Weather in a soft market 

These recent events certainly did not take place in a vacuum. The 2019 season comes on the coattails of the epically large 2018 vintage, which in many cases exhibited yields 35% above the historical average. Unfortunately, this increase coincided with a sudden nationwide drop in wine consumption by over 1%, after many years of consistent annual growth. This collision has caused an unusually soft market, placing tremendous pressure on both growers who are facing low market prices and wineries which have overflowing inventories.  

In years like this one, when the grape and wine industry is flirting with disaster, seasoned industry professionals just shake their heads and say, “welcome to agriculture!” As always, in order for growers and wineries to navigate these stormy waters effectively, their decision-making must be leveraging the most accurate, real-time and high-resolution information.   

Uri Rosenzweig, Senior Product Manager Trellis.ai 

Trellis is harnessing the power of AI a to give the key players in the food supply chain - from growers to food producers – the information and forecasts they need to make better, more accurate decisions, resulting in lower production costs, improved quality, and reduced loss. 

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