The Cost of Frost

It seems that the risk of frost has increased in recent years due to global warming, which does not just warm but makes the climate more erratic and temperatures more extreme (as we saw with temperatures the week before last at 28°C in Bordeaux and everyone at the beach followed by temperatures of down to minus 6°C).

Good news for the moderately temperate climate of Bordeaux where hotter drier summers have produced a string of good recent vintages (2015, 2016, 2018, 2020). But the negative side of this is that frosts have become more common right up until the end of the usual cycle – last year on 6th May.

In the past frost in Bordeaux hit so rarely that we never saw any candles or burning straw bales. Bordeaux vignerons just crossed their fingers and bore the brunt when it happened – in the past every 20 years or so. Past Bad Frosts in Bordeaux – 1956 is legendary with a very cold winter frost some minus 20 °C following a warm period when the sap rose from the roots into the vine foot and branches. It killed the vines. 2017 caused disastrous loss for many on lower land.

The last disastrous late spring frost before 2017 was 1991. Due to global warming frost seems to be striking significantly every two years now and a every year to a degree. Who would have expected the devastation again this year, 2021. Growers are organising protection foe every year now according to their means;

This year April 7th and 8th brought despair to vignerons (and other crops) right across France from Champagne to Cognac, Burgundy (including Chablis 95% loss and minus 7°C), Rhone (particularly Côte Rotie) to Bordeaux as thousands of vineyards’ new growth was obliterated by frost (resulting in zero yield for harvest 2021). It has been called an national ‘agricultural disaster’ and there will be aid. My partner makes wine in St Emilion and when he lost all of this crop in 2017 he was awarded 100€ per hectare – which he never reclaimed.

There may be some new growth and some secondary budding but this is a repeat of 2017 (if not worse) and few were able to harvest any grapes worth speaking of. Perhaps the wealthy vineyards expensive techniques were able to save their best vineyards but most who could afford creating smoke blankets from burning hay bales – they were no match for the frost with temperatures down falling to minus 6 in the worse areas.

Hopefully insurance had been taken out, which involves a substantial expenditure upfront each year (though the payments will not be paid until the wine is usually commercialised some 2 and a half years down the line – in 2023. Many vineyards in lesser known areas (Castillon, Bourg, Blaye, Côtes de Franc, Graves, Satellites of St Emilion) who could not afford these payments and who played ‘russian roulette’, this year lost for perhaps for the last time.

Pessac leognan, Domaine de chevalier

With frost the later it strikes, the more damage it does as the vine has had a chance to bud, grow its first leaves and even buds that will become the flowers and fruit as in 2017. On 27 and 28 April when very warm conditions meant vegetation was 2 weeks ahead of ‘normal’ frost obliterated all vegetation and all possible yield so early in the cycle.

So how does one protect the vines from frost?

  1. Aeolian wind turbines and fans – expensive – some are permanent others you can wheel around to move air around and stop it settling
  2. Air heaters – some are permanent others you can wheel around
  3. Helicopters 1600€ per hour can only fly from 6am but this the coldest time when the sun comes up. Can do 10 hectares. They push the cold air around so that it does not sink down to the ground causing its damage
  4. Candles – usually they last 12 hours so normally can be used for two nights. Cost is 10€ each and you need around 300 per hectare. They do need to be lit and extinguished though.
  5. One can spray with water if you are set up for this via a sprinkler system like irrigation. The vine leaves are protected in their own frozen bubble. Bernard Defaix Chablis see photos below
  6. The most common is burning hay bales. The smoke causes a blanket which heats up the atmosphere. (better than burning rubber tyres like they used to!) You have to be aware of the wind direction and make sure the bales are in the right place. It helps if your neighbours do the same.
  7. Biodynamic producers spray the vines with valerian to give the vines some added fortification to survive themselves
  8. Another product that is sprayed is based on pectins from apples which is supposed to lower the temperature around the vines
  9. Electrical heating cables in Cognac and Southern England – costly alternative
These photos are vines that have been purposefully sprayed with water to protect them with an ice shield at Bernard Defaix Chablis Premier Cru Fourchaume

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