Viticulture 101: Bud break in the vineyard
Like wine? Want to better understand the winemaking process? Most winemakers will tell you that great wines start in the vineyard. So here’s your opportunity to learn more about how wine grapes are cultivated. In our Viticulture 101 series, we will explain the basics of the different growth stages, just as many of Oregon’s vineyards are experiencing them. Follow along as we walk you through the 2016 growing season.
Following our last article on pruning grape vines, next comes bud break. Bud break is actually that– when a new bud bursts out of an existing plant. It’s the first visual cue that dormant grape vines are waking up for the new growing season.
Prior to bud break, the dormant vines begin circulating sap. Farmers can determine if the sap has started flowing by nicking the vine with a knife to see if it bleeds or just by trying to bend the plant. If sap has started to run, it will have a slight give when bent.
Bud break is tied to a number of factors including daytime and soil temperatures. In order for the vines to awaken, the thermometer must hit around 50˚ Fahrenheit (10˚ Celsius) on a regular basis. As the days grow longer, the soil warms, forming a perfect environment for the plants to wake from their winter slumber. But not all soils are created equal either– rocky soils warm faster than clay since the rocks absorb sunshine and radiate that heat out as the evening cools.
Clone type is another determining factor as to when bud break will begin. While there are many varieties of winemaking grapes including Pinot noir, Chardonnay, Riesling and Cabernet sauvignon, over the years, each has mutated out in the vineyard. These mutations are spontaneous, natural occurrences. For example, a farmer might find that one particular plant grows slightly larger clusters than the other plants in the vineyard. So the next year he grafts a cutting from that plant and begins to propagate this new trait. Over time, this vine may be considered a new clone. Now we have clones such as 777, Wadenswil and Pommard, each with slightly different attributes, yet all still Pinot noir grapes from the same parent plant. And bud break varies, depending on the clone. All grapes follow a similar growing cycle but some clones start growing earlier than others. It’s similar to apple varietals– there are Fuji, Granny smith and Pink lady, etc., but they’re all still apples.
If wine growers choose a clone that experiences bud break later in the spring, their grapes might not have time to fully ripen before the growing season begins to cool again. Conversely, grape clones with an early bud break run the risk of being damaged by a late spring frost.
Bud break is happening all over the Willamette Valley. If you’re not able to make a drive out to wine country, search for winery and vineyard photos celebrating bud break on various social media channels like Facebook, Twitter and Instagram. And now that you understand bud break, stay tuned as we continue our Viticulture 101 series through the rest of the grape-growing season.