GROWING SEASON BULLETIN 3: AUGUST 2010
SEASONALITY AND FARMING: Fearsome Weather for Cabernet Sauvignon
2010 GROWING SEASON WEATHER is being affected by an El Niño-Southern Oscillation (ENSO) , which produces low quality when it rains by Fall Equinox in regions I, II and III. The risk is to the late maturing grape group (LMGG): Cabernet Sauvignon, Sangiovese, Grenache, Carignane, Zinfandel, and Nebbiolo. Critics’ vintage charts show low 100-point scores for ENSO vintages such as 1998.
ENSO produces fearsome, cold wet, winegrowing weather in California and Oregon. El Niño is the warm phase, which ended in June. La Niña is the cold phase, which began in July and is predicted to strengthen in August. Quality crashes when a winegrowing season is bookended by both.
This is the coldest growing season in over a decade. Your farming practices should include managing water availability by irrigating as a function of Leaf Water Potential (LWP), and dropping crop in vineyards when the yield is over 3 tons per acre, to maximize color development.
Following is the information you will find in each bulletin for the 2010 growing season:
June, Bulletin 1: Days-Bloom-To-Harvest Model.
Grape Growing Maturity Groups are groupings of varietals distinguished by differences in time required from bloom to full ripeness at a standard temperature. Grape Growing Maturity Groups are groupings of varietals distinguished by differences in time required from bloom to full ripeness at a standard temperature. This length of time is calculated as Days Bloom to Harvest. Pinot Noir, classified here in the Burgundy Maturity Group, bloomed on May 24 in Carneros. The calculated harvest week is therefore September 10.
July, Bulletin 2: Growing-Degree-Days Model (Part A) and Viticulture Tips for July (Part B).
The first part of this bulletin explained Growing-Degree-Days. Each Grape-Growing-Maturity-Group has a specified requirement for heat accumulation to achieve ripeness, which is measured in Growing-Degree-Days. The Days-Bloom-to-Harvest model, explained in Bulletin 1, is decreased or increased based on variations in heat accumulation vs. the 10-year average.
August, Bulletin 3: Seasonality and Farming.
Environmental factors and farming techniques change harvest dates and taste quality for all Grape Growing Maturity Groups. Seasonal water availability requires winegrowers to change August farming plans to improve harvest date and taste quality. Winegrowers will adjust irrigation to accommodate for the large canopy and delayed verasion by irrigating more. Winegrowers will adjust crop levels to further change the outcome.
September, Bulletin 4: Measuring Vineyard Performance.
The GrapeFAX Index™ will help you determine the optimum day of harvest. We will provide an in-depth analysis of the Enologix GrapeFAX data to determine color and flavor accumulation.
BULLETIN 3, PART A: HARVEST PREDICTION BASED ON DAYS BLOOM TO HARVEST AND GROWING-DEGREE-DAYS
Seasonal heat summations to date predict that the harvest is as much as 2 to 3 weeks behind as predicted by the Days-Bloom-To-Harvest Model adjusted for Growing-Degree-Days (GDD) in Northern California. Seasonal GDD measurements show we are behind schedule by 15-25%.
Field Report: The El Nino warming cycle in the winter of 2009-2010 gave us our first growing season with water availability in four years. This has caused significant vegetative growth that is still growing in Napa Valley. Low GDD in June and July has both increased water availability and delayed veraison. The first berries began to turn red for Cabernet Sauvignon, Syrah and Zinfandel on August 1 in Napa and Sonoma Counties. Pinot Noir veraison has been underway for less than a week in the Sonoma Coast and Russian River Valleys, and is just beginning in the Central Coast. Early reports indicate that Veraison is progressing normally. The weather outlook for the next two to three weeks indicate that heat spikes are not in the forecast, which means that veraison should proceed normally.
Large canopy size means the vines have more demand for water than normal. Even though the wet winter has replenished groundwater, the extra demand will deplete groundwater stores. We are recommending winegrowers increase water availability with irrigation and keep water stress to a minimum. This situation makes it vitally important to irrigate more aggressively than normal.
Overall, 2010 GDD are lowest since the 1998 growing season, Table 1. Most regions are 15-25% behind. GDD for Oakville is equivalent to 1998. Every other region is colder than 1998. Paso Robles is 26% below the 10-year average. We have completed four full months of the official growing season (April through July) and have enough data to predict that Harvest should be 124 days from bloom for Cabernet, 120 days for Syrah and 116 days for Pinot Noir in Oakville. These predictions are behind for all varietals in all regions.
Table 1: 2010 Growing-Degree-Days
The lowest GDD for the first four months of the season was in Arroyo Seco, where the major varietal is Chardonnay and Pinot Noir. The highest GDD was in Oakville where the major varietal is Cabernet and Syrah. As of August 1, aggregate GDD for 2010 is 15% below the 10-year average in all California appellations except for Paso Robles, which is 26% cooler than normal. Based on GDD data, we have updated predictions for harvest for northern and central California, Table 2 and 3.
HARVEST PREDICTION FOR NORTHERN AND SOUTHERN CALIFORNIA
Predicted Harvest Dates—Northern California
We have used the updated GDD data to update our original Days-Bloom-To-Harvest Model and the 2009 bloom dates to fine tune our prediction for the week of harvest for Northern California in Table 2 below. Growing-degree-day data through July 31 has resulted in a second upward adjustment in the calculated Days Bloom to Harvest for each region by 2 to 3 days. This pushes the predicted harvest date to September 13 for Pinot Noir.(Please see Appendix A on page 7 for our calculations.)
Table 2: Northern California Harvest Dates (average 18° - 38° C)
Predicted Harvest Dates—Central California
GDD measurements have significantly affected the original harvest prediction in Central California. Cooler than normal temperatures in Paso Robles has extended the harvest date by 4 days. Cool temperatures in Santa Ynez have pushed back the harvest date by 3 days. The predicted harvest for Burgundy has been pushed back to September 23, as shown in Table 3 below.
Table 3: Central California Harvest Dates (average 17° - 36.6°C)
BULLETIN 2, PART B: FARMING PRACTICES FOR AUGUST
Farm as if it Will Rain
Late ripening varietals will be in danger if it rains by the Fall Equinox. Burgundy varietals look like they will ripen by the Equinox.
Winegrowers must have a plan over the next several weeks to maximize ripening in the event the ENSO yields rain by the Fall Equinox. This includes irrigation, crop thinning and tracking flavor development. The goal is to create a two-week window before the fall Equinox within which grape quality will rise more rapidly than normal. Two proven ways to accelerate color development is water availability and to drop crop before 100% veraison.
Irrigate Your Vineyards
Conventional wisdom tells us that the rainy winter weather conditions in 2010 means we can irrigate less than we did in 2009. This is the wrong strategy. It may seem counterintuitive, but the large canopy requires much more demand for water to keep the vines active. The vines will stress once the moisture is pulled from the ground and will arrest flavor development. Keep water stress low (-10 - -12 millibars in the morning) and irrigate aggressively to maximize flavor accumulation in the berries and to moderate the rate of sugar accumulation.
Crop Thinning
Now is the time to make a plan to drop crop to account for the Seasonality. The goal is to maximize ripening in the two weeks prior to Fall Equinox (September 7 – 21). For late ripening varietals, (120 DBH) thin your crop as a percentage of days from bloom to September 7 divided by 120. Caveat: Don’t thin your crop if yield is below 2 tons per acre.
For example, if a Cabernet Sauvignon vineyard bloomed on June 1:
Days Bloom to September 7 = 99 days / 120 days = 83%; Thin crop by 17%
Track Vineyard Performanc with Enologix
This difficult growing season makes it especially imperative to track quality accumulation in the vineyard to determine picking date. This year, we recommend tracking performance of each block at the same 22°, 24° Brix, and again at the predicted harvest date by DBH. Contact Enologix for minimum performance metrics for each varietal.
Questions?
Feel free to contact us at 707-938-9463.
APPENDIX A. HARVEST PREDICTION CALCULATIONS
As of August 1, 2010, Growing Degree Day data was used from our June 1 prediction of September 10 for Pinot Noir. The addition of 3 days is based on heat summations through July 31.
The equation for predicting dates of harvest of September 13 is as follows for Northern California Pinot Noir:
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