Home Industry News Releases Unusual Cool Growing Season Extends Bloom Period for Napa Valley Wine Grapes

Unusual Cool Growing Season Extends Bloom Period for Napa Valley Wine Grapes

Photo courtesy of Robb McDonough and NVG.

Napa, CA (June 11, 2015)Napa Valley’s unusually cool start to the wine grape growing season has extended the stages of flowering and fruit-set for the 2015 vintage by up to three to four weeks, according to the Napa Valley Grapegrowers (NVG). This is later than anticipated despite this year’s early bud break that started the growing season.

Heat spikes in Napa this week may “speed up” the development of this year’s wine grape clusters, but as of now, growers report that this vintage is one with the slowest blooms on record.

The flowering and fruit-set stage is an important time in which fertilized flowers begin to develop seeds and grape berries. This phase is critical for wine production since it ultimately determines the potential crop yield.

A lengthened bloom period is unique for Napa and has created wide variability in wine grape clusters. NVG members are closely watching the clusters and will manage them at the time of veraison, the onset of ripening, if a lack of uniformity continues.

“Because of the variability in this year’s fruit set, crop thinning at the time of veraison will be even more important to even out the maturity of the clusters,” said Allison Cellini, NVG member and viticulturist at Cliff Lede Vineyards. This is accomplished by removing later ripening clusters, to adequately ripen the remaining fruit in a more uniform manner.

“The recent cool-down in temperatures that we’ve seen across the board has elongated the bloom period in some vineyards to as long as four weeks. The effect this will have on harvest remains to be seen, but the incredibly early season that we were looking at a month ago has definitely been pushed back,” said PJ Alviso, NVG member and Director of Estate Viticulture at Duckhorn Wine Company.

NVG reports that wine grape growers have also faced heat spikes and rain in the past two weeks. Both in-the-field technology and hands-on farmworkers are managing these issues to assure high quality grapes. With veraison expected to begin in the next three to four weeks, Napa wine grape growers will continue to proactively address these variability factors now, in order to achieve the highest quality fruit for which the Napa Valley is renowned.

About Napa Valley Grapegrowers

The Napa Valley Grapegrowers is a non-profit trade organization that has played a vital role in strengthening Napa Valley’s reputation as a world-class viticultural region for over 40 years. Its mission is to preserve and promote Napa Valley’s world-class vineyards. NVG represents over 690 Napa County grapegrowers and associated businesses. For more information, visit www.napagrowers.org.

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