Rain Dance: Navigating the 2021 Harvest
Vintage 2021 may have been our first climate change test. Every weather event we witnessed was what meteorologists predicted a decade ago. Extremes and fluctuations demanded patience, meteorological fluency, and vineyard intimacy.
Rain defines our vintages. Its impact on vines, grapes and wines is complex. This vintage supported past observations that factors beyond precipitation amounts such as soils and slopes, temperature, post rain weather and vine age all contribute significantly to grape health and ripening. Water influences three separate but inter-related aspects of winegrowing.
I. Soils
Everything from vegetative growth to juice concentration is regulated by a soil’s Plant Available Water (PAW) and resulting vine hydric stress. There are four stages where soil moisture plays a role in wine quality.
Post bloom period. During berry enlargement PAW influences berry size. Some hydric stress makes for smaller berry size which reduces rot potential and increases flavors.
Veraison. Hydric stress in mid-summer results in quick and uniform color change and ripening which is especially important for high quality red wines.
Post veraison. Low PAW prevents stimulation of competitive shoot growth which allows the vine to focus solely on ripening grapes.
Ripening. High PAW (wet soils) at ripening will result in:
a. Juice dilution
b. Berry swelling, rot potential, and compromised, weakened skins
c. Berry cracking.
II. Weather During Ripening
Temperature
The temperature during and after rain has a bearing on rot development. Warm, wet conditions trigger sour rot which has a highly detrimental quality impact on resulting wines. Rainfall when temperatures are over 70 F (21 C) can result in fast developing sour rot. Rainfall in the 60F (15 to 21 C) range slows the development of sour rot. Under 60F (15 C) sour rot is rarely a problem, but botrytis and ripe rots can still slowly develop.
Drying
Weather conditions post rain are perhaps the most important aspect of the vine’s ability to recover from rain. Low dew points (humidity), wind and sun all greatly reduce rot development and assist in berry water loss.
III. Vines
Vine age
Old vines are more resilient to rain at harvest than young vines. Their more established and deeper root systems moderate water uptake. At around eight years old I’ve noticed that vines handle extremes better, then at around twenty years their ability to handle rains is significantly superior to younger vines.
Cluster architecture and skin thickness
Petit Manseng has thick skins and loose clusters. It is resistant to rot. Riesling has thin skins and tight clusters. It has rot in most years. But there is a middle ground that depends on not just variety, but also clone, soil fertility (nitrogen), and PAW during berry development post bloom.
When to pick: Hold them or fold them?
Picking decisions in 2021 were stressful and difficult. The harvest was defined by cycles of rain and then the promise of fine weather.
In August 2021, the first rain events were welcome as some vineyard blocks were going into extreme hydric stress. We experienced a couple of rains of around 0.5 to 0.7 inches (12 to 18 mm). These rains refreshed the vines and were welcome. Then came a cycle of much heavier 1.5 to 2.5” (38 to 60mm), but short duration rains that eventually saturated the soils. This stimulated shoot tip growth. Grape ripening and new vegetative growth were in competition. Fortunately this occurred after a fast and uniform veraison which contributed to the success of red wines. In fact, the July/early August drought probably saved the vintage as the resulting small berries and loose clusters were more resistant to rot and uniform veraison gave a boost to red wine quality.
Soils remained moist through harvest. But additional rains did not have their usual significant impact as far as berry swelling and dilution. The vines seemed to have acclimated to having continual access to water. Nevertheless ripening slowed and flavors were uninspiring.
Harvest started late (Sept 10) as we waited for flavors and skin phenols to develop and acids calm. Berry sampling and lab analysis were eventually abandoned as it became apparent that cluster integrity and flavor development would trigger picking. I spent a good part of most days walking the vines and tasting grapes.
Know your rots
I spent most of harvest tasting compromised berries in the vineyard. I needed to understand what kind of rot was developing and how it would impact wine quality. Grape integrity determined when to pick. Fortunately, sour rot was a factor in only certain sections of high vigorous Riesling and Sauvignon Blanc vines. Sour rot is a nightmare and can ruin wine potential even in small amounts.
As September temperatures cooled we saw very little sour rot, but ripe rot became more of a player. I can live with low to even moderate levels of ripe rot (and botrytis) in white grapes. In fact I do believe that the 2021 white wines benefited from a degree of concentration coming from infected berries.
By late September our red grapes were just starting to turn a corner. Clusters from young vines were becoming fragile to the point where they would start to fall apart with more rain. While they were not ripe enough to make noteworthy red wines, they were in a good window for rosé. Old vine fruit held up well. The test came on after a big rain on September 22. There was some berry cracking and some ripe rot, but we held off picking as weather conditions turned perfect with cool temperatures, low dew points, wind and sun.
The compromised berries dried up. Rot stopped in its tracks. Ripening proceeded. The berries lost water and gained some intensity. The red vintage was salvaged. We held off picking as long as possible in order to take advantage of every hour of sunshine. Wine style was shaped by rain: elegant and feminine. As winemakers we respected the vintage by employing gentle extractions and very little new oak.
Rain during harvest is rarely celebrated. But this is a reality of our climate. Intuition and experience will play an ever greater role in making great wines as climate change takes charge. Vintage variation will become more pronounced and winegrowers will need to be flexible and change course mid-stream. We are extremely pleased with the quality and style of the 2021 vintage. But getting there wasn’t easy.
Grape Press, December 2021
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