When frost throws its two cents in

 

The beginning of spring is a crucial time for the vines. The completion of pruning and the arrival of buds determine the quality of the year's harvest. This week, winter temperatures made a strong return after a mild start to March. While the vines had approximately 15 days in advanceThis cold snap caused widespread damage, particularly in Provence, the Rhône Valley, and the Gard region. What are the risks to vineyards when spring frost intervenes?

Spring: the awakening of the vine

In March, winter pruning prepares the vine for the next harvest. It determines the plant's good fruit production in the following months. 

This is about select the most promising buds And separate from the weakestThese choices determine the quality of the next harvest. The pruning team has a significant responsibility and must therefore be carefully trained. 

The most promising buds are those that appear on one-year-old wood. First and foremost, dead wood and shoots growing at the base of old wood must be removed. The aim of pruning is to make room for new growth. The winegrower prunes the vines after periods of hard frost.

The frost in spring 

In spring, the vine awakens and budbreak occurs. In other words, the buds open and reveal leaves. Pruning must be completed by the time of budbreak so that the vine can develop properly.

These buds can withstand temperatures down to -3°CHowever, the nights of March 24-25 and 25-26 saw... temperatures around -5°C In the Var region, for example, unprecedented temperatures are having a lasting impact on the vines. The cool temperatures this week risk freezing the vines and "burning" the plant. Parts of the vine may die, and grape production could be significantly reduced this year. It is still impossible to know the full extent of the damage because we don't know if the inside of the bud is affected.

Frost protection techniques 

Of course, some techniques exist to limit frost damage at this time of year. These involve warming the air around the vines to limit the increased cooling of the vineyard. 

• Candles or hand warmers These are blocks of paraffin in metal boxes that are placed in the middle of the vines to warm the ambient air. 
• Fans, wind turbines, or helicopters Systems are put in place to circulate the air and thus distribute it more widely in the vineyard in order to warm it up.
• The spraying This technique involves spraying the vines with water until temperatures rise above freezing. The pipes and sprinklers are expensive and are only installed on plots most exposed to the risk of frost. 
• Propane burners : You need 150 burners per hectare, to be placed within the vineyard in order to heat the air.

Some of these solutions are very expensive or require a large workforce. However, with the COVID-19 pandemic, vineyards are unable to mobilize teams to work in the vineyards. Added to this is the environmental problem. Indeed, the use of candles, burners, and sprinklers can impact air pollution and significantly increase water consumption.

The impact of frost on the vine

As we understand it, it is still difficult to know the true consequences of this spring frost on the 2020 production. Three main scenarios are possible:

• Less than half of the buds are affected and the climatic conditions are favorable, so the vine will compensate for the losses on its own by favoring the remaining buds. 
• Half the buds and less than ideal weather conditions mean that production is likely to be low. However, a small number of grape bunches on the vine can concentrate aromas and thus produce high-quality wines.
• Beyond 60% damage on the buds, the harvest may be zeroWe need to produce branches to ensure the harvest the following year. 

To mitigate the significant risks to the vineyards, temperatures need to rise. In any case, winegrowers are embarking on a real marathon. It's not about providing temporary care to the vines, but rather about protecting them sustainably against winter temperatures. For now, the weather forecast doesn't suggest a rapid improvement. These unprecedented conditions and the lockdown make the winegrowers' mission even more perilous; this is a developing story…

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