A critical moment: the risk of frost

Budding and bud break on the vines is already a fact and we are entering one of the most dangerous stages for vineyard cultivation: spring frosts. These are usually early frosts that affect the buds once the activity has started and can devastate the future crop. A well-known example was the frost at the end of April 1999 in Rioja, which took a huge toll on expected grape production and sent grape prices soaring to 2.55 euros per kilo.
Each wine-growing area has its own moments of maximum risk, depending on climates and microclimates, and, for example, in Rioja, the date marked on the calendar is San Marcos, April 25, since usually by then, with the buds sprouting, the damage in the vineyards is usually very significant.. “Marcos, marquete, vendimiador sin corquete”, the saying goes.
In Ribera del Duero, an area much more exposed to frost due to its continental climate -both in spring, early, and in autumn, late-, alerts can be maintained until practically the month of June. ” The frost of Santa Rita (May 22) takes everything away”, says the local proverb. In fact, there are several wineries in Ribera del Duero that use air towers that take the air at altitude (at a higher temperature) and propel it towards the vines.
Even more spectacular are the images we saw last year in Chablis (France), where winegrowers set fireplaces and fires among the vines, sprinkled water on the vines and started large fans to fight a frost of -4 degrees on April 27.
Frost can be classified into three main categories: advection, irradiation and evaporation. The advection frosts are caused by cold waves of cold polar winds gusting from the north. They are more common in winter, when the plant has not yet sprouted. Radiation frosts are the most common in spring and therefore the most feared. They are typically associated with cold and dry anticyclones that are accompanied by cloudless and windless nights. Finally, we have evaporation frosts that are produced by the loss of heat from the plant when the dew deposited on it evaporates rapidly.
For winegrowers such as Familia Martínez Bujanda these are moments of great tension because the work of a whole year can go down the drain. There are techniques and field practices that help prevent frost, such as late pruning (delaying bud break), of course the selection of vinifera (later budding) and the choice of site for the vineyard, vineyard management (raising the height of the clusters), moistening dry soils in winter, avoiding soil tillage and we also have the ‘artificial’ methods mentioned above such as fans, stoves or sprinkler irrigation.
Year of snows… year of goods’, the saying goes. We haven’t had them this winter, but we certainly wouldn’t want to see a white field from now on.

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