By Michelle Moyer, Viticulture Extension Specialist
By many accounts, 2011 has been a challenging year across the state. Patchy, yet severe, cold damage from the “Thanksgiving Freeze” in 2010 has many vineyards starting over, or at significantly reduced yields due to loss of the primary fruiting buds. This was followed by late-spring frost damage in some sites at the end of May. Finally, 2011 is lagging in growing degree day (GDD) accumulation (Table 1). Across the region, we are ranging 243 to 369 GDD units behind 2003, which was considered a warm year. We are ranging 35 to 128 GDD units behind 2010, which was considered a cool year.
|Table 1: Growing Degree Day accumulation (base 50°F) from April 1 to July 4, for 2011, 2003 (warm year) and 2010 (cool year). All data was accessed from AgWeatherNet (AWN) (www.weather.wsu.edu).|
||2003“Warm Year”||2010“Cool Year”|
|Puget Sound- Mt. Vernon||345||588||380|
|Rattlesnake Hills: Outlook||609||963||717|
|Yakima Valley: WSU-HQ||612||896||678|
|Lake Chelan: Chelan South||613||n/a||701|
|Walla Walla Valley: Walla Walla||628||918||689|
|Snipes Mountain: Port of Sunnyside||629||930||723|
|Columbia Gorge: Mary Hill||641||n/a||719|
|Wahluke Slope: Mattawa||708||1072||803|
|Red Mountain: Benton City||730||1099||822|
|Horse Heaven Hills: Paterson||768||1052||866|
Bloom is slowly coming to an end in Eastern Washington, for both juice and wine grapes. As a historical reference, the average first bloom for Concord is June 1, indicating we are about 3-4 weeks behind “schedule” in most areas.
However, this means very little when speculating on fruit quality and when it will ripen. If you look closely at GDD in Fig. 1, the warm 2003 and cool 2010 growing seasons started similarly, but had drastically different endings. A warm spell in May initially separated the accumulation curves, but the really difference came in mid-July. It truly is the temperatures in July, August and September that can determine a vintage. It is too early to predict how and when grapes will ripen, as we cannot predict with sufficient accuracy how the weather will progress in these critical months.
If we compare 2011 to 2003 and 2010, we can calculate a “best” and “worst”-case scenario. From July 4 to Sept 15, 2003 accumulated 1653 GDD, totaling 2549 GDD; 2010 accumulated 1359 GDD, totaling 2037 GDD. If the current season accumulated the same GDD as in 2003 or 2010, it would place us at 2265 GDD and 1971 GDD by Sept 15, respectfully. In an “average” year, we would accumulate 1395 GDD (based on data from 1924-2010), which would place us at 2007 GDD for 2011. With an average daily accumulation of 14 GDD in September, we could be (at Sept 15) approximately 16 days ahead of 2010 if we have the best-case scenario of warm temperatures, 5 days behind of 2010 if we have the worst-case scenario of cool temperatures, and 2 days behind 2010 if we have “average” temperatures. These forecasts were based on data from WSU-HQ only.
Conclusion thus far: Should temperatures stay cool, the vintage may be delayed compared to last year. Even with a delay, we will have enough time to ripen fruit, as climate conditions in Eastern Washington are conducive to reach sufficient sugar content without the presence of unripe flavors. However, with cool vintages, this ripeness may not correspond to traditional harvest parameters vintners in the area are accustom to, it therefore is important to harvest based on flavor development, not numbers. If cool temperatures persist, winemakers may have to adjust their practices as in 2010 to work with fruit that has more acidity (more malic acid) and lower pH. In 2010, these adjustments were often made by using malolactic fermentation (even in some wines were it was not typically used) and by doing small chemical deacidifications in the must and/or the wine. Information on chemical deacidification and malolactic fermentation is available at http://wine.wsu.edu/research-extension under “Articles”. More information on MLF workshops on July 12 and 14 is also available on the website.
Article was prepared with enological input from Dr. Thomas Henick-Kling, Director of Viticulture and Enology, WSU-TriCities.