Five Fast Facts about Budbreak

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Despite the craziness of the world around us, the natural cycle of life continues. One of the most fascinating to witness—for students of wine—is the life cycle of the vineyard. For those of us in the Northern Hemisphere, we are witnessing the blooming of spring—and along with it—the breaking of buds in the vineyard.

In homage to this annual miracle, here are five fast (fascinating) facts about budbreak in the vineyard.

#1: In a typical year in the Northern Hemisphere, budbreak will begin in mid-March. In years of oddball weather, it may begin to occur as early as mid-February or as late as mid-April. In the Southern Hemisphere, the process typically begins in mid-September, but can be as early as August or as late as October.

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#2: Within a single vine, those buds that are furthest away from the trunk will break first; in some cases, this may occur several days before those located closer to the trunk. This is particularly apparent when canes are left upright; in such cases the buds furthest from the trunk (the more distal buds) will be observed to burst several days before those closer to the trunk (basal buds). This phenomenon, known as apical dominance, can be avoided by bending or cracking the cane.

#3: The most direct correlation between mother nature and budbreak is the cumulative effect of the warming air temperature once it hits an average of 10°C/50°F. This temperature is sometimes referred to as the “growth threshold” and will signal the nascent buds to shed their fuzzy exterior and break free. Soil temperature may also be a contributing factor, so a wet-and-cold late winter (resulting in wet soils that retain the cold temperatures) can slide bud break back a few days or weeks. (According to the website of Penn State Extension/Wine and Grapes there is conflicting information on whether or not soil temperature affects the timing of bud break. In some studies, Cabernet Sauvignon vines show a correlation between the date of bud break and rising soil temperatures. Alternatively, some studies show no correlation between soil temperatures and the timing of bud break in Syrah.) Other factors that influence the timing of budbreak include photoperiod (day length) and chemical (hormonal) plant growth regulators that help to maintain the plant’s period of dormancy even in the face of mid-winter warm spells.

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#4: While many factors contribute to the timing of budbreak in a given vineyard in a given year, some varieties are known for their tendency towards early budbreak. Likewise, some grapes tend to be late breakers. Here is a list of some of the better-known varieties, arranged by their tendencies regarding bud-break and ripening:

• Early bud break/early ripening: Chardonnay, Pinot Noir, Merlot
• Early bud break/mid-to-late ripening: Chenin Blanc, Grenache, Viognier
• Late bud break/early ripening: Sauvignon Blanc, Syrah
• Late bud break/mid-to-late ripening: Riesling, Cabernet Sauvignon

#5: Fun with fruit trivia: Grapevines need a slightly higher base (air) temperature than is required to induce bud break in many other fruits. Fruit trees such as apple, peach, cherry, and apricot tend to break bud when the average air temperature reaches 39° to 41 °F (3.8° to 5°C).

The most important aspect of bud break, at least in my opinion, is that is represents the hope for a successful year, to be followed by flowering, fruit set, veraison, ripening, harvest, and (several months or several years later) more wine for all of us lucky humans. Bring on the buds!

References/for more information:

• https://psuwineandgrapes.wordpress.com/2018/05/14/grapevine-bud-break-101/
• http://arrowheadwine.blogspot.com/2012/04/out-of-deep-sleep.html
• https://blog.jordanwinery.com/grape-bud-burst-pictures/
• https://tablascreek.typepad.com/tablas/2019/04/budbreak-2019-we-celebrate-a-late-beginning-after-a-wet-chilly-winter.html
• Robinson, Jancis and Julia Harding: The Oxford Companion to Wine, 4th Edition. Oxford, 2015: The Oxford University Press.
• Robinson, Jancis, Julia Harding and José Vouillamoz: Wine Grapes. New York, 2012: Harper Collins Publishers

The Bubbly Professor is “Miss Jane” Nickles of San Marcos, Texas… missjane@prodigy.net