How winemakers fight the cold ?

With cold waves and spring frost, vines are subject to very low temperatures. Spring frosts can go down to -9 ° C. Vines may lose their buds and winemakers may lose production. Crops can be lost due to frost. Here are some tips to fight against freezing of vines, and hope to limit the damage.

Thanks to these beautiful photos, we'll be able to see how the winemakers fight against the cold and the inclement weather.

Between buds and cold

Early arrival of buds

From March, we could see the first buds — so-called eyes — from the vine to appear. These eyes appear during the winter and are protected by thin woody film. The weather being mild at the end of winter, they came out earlier than usual.

With good temperature and humidity conditions, the sap starts circulating, causing the bud to swell. This is when the protective film spreads to reveal a down : we call it "la bourre". It's time for "disbursement".

The bud continues to swell and lengthen to make the first leaves appear between late April and early May : this is called "leafing". With 10 to 15 days ahead of normal, the first leaves formed and the weather was much less lenient…

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Extreme cold : a historic black frost

Severe frosts have plagued many vineyards including Burgundy and Indre-et-Loire and the cold has persisted for several days. Jean-Michel Aubinel, President of the Confederation of Burgundy Wine Appellations was very concerned about the situation : "It's quite clearly a historic frost, close to the one of 1994, and maybe of 1991 ".

The first bad weather occurred on 13 April afternoon in the south of Mâconnais. A historic hailstorm for many reasons :

The time of year,
The duration of about 20 minutes,
Intensity with hailstones up to two centimetres in diameter
The area with more than 2,500 hectares affected

In the first villages affected, the first estimates show 80 to 100 % buds and small leaves torn or slashed.

A few days later, second blow for the region's winemakers. The frost settled in the area with a peak in the night of the 26 to 27 April. Almost the entire Burgundy wine region has been affected, only Beaujolais and Mâconnais were spared.

On average, temperatures have not dropped below – 3 degrees which is not an exceptional thing. Only here it is, all the conditions were right to make this frost disastrous…

Ambient humidity caused by rain, even the snow of previous days,
A fragile vine with the appearance of the first leaves,
Almost no wind,
And a strong radiation at sunrise.

Fortunately, in the coming weeks, secondary buds will certainly grow, which will certainly compensate for some of the losses currently observed. Flowering is also a very important stage, but without hesitation I can tell you that the cellars will not be full for the vintage 2016.

Winemakers' solutions against bad weather

The fight against hail

The anti-hail cannon

No studies have confirmed the effectiveness of the anti-hail gun, I would not dwell on the issue. If you want to learn more about this method, a link is available at the bottom of the page.

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The hail protection net

Since 2014, hailnets are experienced in burgundy. These nets installed year-round are raised when the winemaker wishes to intervene on the vine. Once the net is positioned, fine mesh prevents hailstones from impacting leaves, buds or fruit. It is estimated that, this system is reliable at 90 %. Unfortunately, although this solution shows important results, it also has significant drawbacks for the winegrower.

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Its installation cost varies between 10’000 and 16’000 € / ha for a lifespan of 10 to 15 years and operating costs of the order of 300 € / ha / an. This system can also make it more difficult to work mechanically on the vine.

Cold insurance

The last solution against hail is insurance. Unfortunately, in 2009, "Only 100.000 hectares of vines on 800.000 are insured against hail in France", according to the president of the specialized wine council of FranceAgriMer. according to the chairman of FranceAgriMer's specialist wine board : The cost of multi-risk insurance, is estimated at 2.600 € / ha / year is not profitable compared to the cost associated with a possible loss of 100 % of the harvest.

The fight against black frost

There are many techniques. I'm going to introduce you here to the two main and most impressive. You have to realize that the work of winemaker has no hours and many of them have been watching all night to monitor the vines, because at the slightest misstep, it's the whole vineyard that can be wiped out.

Candles to warm the vines

— But why are they setting fire to the vines ? — One obvious way to fight the cold is to warm the vines. If a period of black frost is expected in the coming nights, the winemaker then decides to install candles in his rows of vines. Wax compounds 100 % of natural origin, they have a lifespan of approximately 8 hours, and aim to warm the air and soil to prevent the buds from freezing.

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Water to fight black frost

This method may surprise, but remains very effective in cold weather. Winemakers water the vines to limit the drop in temperature to 0 degree. This may seem paradoxical, but is very effective at protecting the vines. When water sprayed on vines turns to ice, calorie release occurs. The ice cocoon that forms around the bud then maintains the internal temperature at 0 degree while the outside temperature may drop to less than 4 degrees.

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During this period of extreme cold, the winemaker must water until the ice melts. It's only once the ice has melted, that the winemaker can stop watering his vines, because the transformation of water into ice and this release of calories has to be done all the time.