The vine is a living element, often very sensitive to very low temperatures. As soon as the first buds appear on the vines, waves of frost and cold are a real scourge for winegrowers, who risk losing everything in the space of a few hours. Fortunately, there are solutions to help winegrowers fight against frost .
Warm the vines to counter frost
When the sunny days return, the buds and the first leaves appear in the vines. And even if they are rather resistant to cold (up to -3°C), negative temperatures can freeze the sap and burn the bud , which will no longer be able to develop. Winegrowers then use several techniques to warm the air surrounding the vines during a frosty night, and thus avoid the dreaded major damage.
Candles and braziers
When negative temperatures are forecast, winegrowers resort to the most common vine warming technique : the candle . This involves placing large candles throughout the vineyard, made of blocks of paraffin poured into metal boxes. The winegrower can also choose to install braziers in the middle of the vineyard. And to facilitate the circulation of hot air in the vineyards, it is possible to add heating fans .
The candle or brazier technique allows you to heat the ambient air and avoid a sudden and significant drop in temperature. The buds are thus preserved, and can produce beautiful grapes to produce wine.
The heater is a heating device to combat spring frost on vines and branches. It operated on fuel oil for a long time, but more and more models of heaters today operate on wood or pellets.
Although the installation of heaters offers a nice spectacle at night, this technique has the disadvantage of emitting CO2, and therefore of being polluting.
Good to know: heaters, candles and braziers are very effective during a frost episode, but require significant labor to install them.
The sprinkling technique
The anti-frost spraying method consists of spraying water on the vines before the frost period. The buds are then encircled in an ice pack in which the water is not frozen. This is called the supercooling phenomenon.
However, it must be recognized that this technique is very difficult to master, and the sprinkling must be continuous throughout the frost period, otherwise there is a risk of the ice cube thawing too quickly and damaging the vines.
Although it is very effective, sprinkling is therefore an expensive method of combating frost , because sprinklers and pipes must be installed upstream.
The propane burner is an antifreeze solution that is economical, low-polluting and automatable. This involves placing propane burners throughout the vineyard to prevent freezing (around 150 burners per hectare of vineyard).
The wind turbine has the advantage of mixing the air, and thus directing the warmer air from the ground towards the vines. The anti-freeze wind turbines are small (11 meters high), and are placed around the vineyard.
Another air mixing technique, the helicopter acts in the same way as the wind turbine. If the method is very effective, it remains expensive, but above all dangerous, because the helicopter flies at low altitude, only 20 meters above the ground, and with little visibility (at dawn, before sunrise ).
When should frost control measures be activated?
The choice of whether or not to activate the means to combat frost is a crucial decision, which determines the survival of the vine. You also need to know how to implement solutions at the right time, and adapt according to the stage of development of the vine .
The earlier the development stage, the more resistant the vine will be to low temperatures (up to -7°C before the flower buds appear). As soon as the flower buds appear, anti-freeze devices should be used as soon as the temperature drops below -2°C. Finally, from flowering and until the fruits appear, you will need to be vigilant as soon as the weather forecast calls for temperatures below -1°C.
Frost is a real danger for vines, and winegrowers are always on the lookout for severe cold weather, particularly spring frosts, which can be devastating. Fortunately, there are many anti-freeze solutions available , and wine growers can be alerted in real time of frost risks using connected frost sensors.