In the last ten days we have been reading a lot about the dreadful frosts that have occurred throughout France and how this has affected vineyard regions.
At this time of year, frosts can be fatal to the vine as the young buds begin to emerge from their winter slumber. Research has shown that for a Pinot Noir vine, for example, half the buds can be damaged if subjected to -2.2 degrees centigrade during bud burst. If the leaves are exposed, then a temperature drop to just -1 degree centigrade can be enough to damage the buds.
What does this mean to the vine?
If the vines buds have burst open and leaves have begun to form, then the next stage will be flowering, which in the northern hemisphere tends to take place around 6-13 weeks after budbreak. If the buds have been frosted, then no flowering takes place, meaning no grapes will form. Other buds may appear elsewhere on the vine to replace the damaged ones, but on most vitis vinifera vines (or the noble vines we use for quality wine production), these secondary buds do not produce good enough quality grapes.
It can take a week or two to assess the exact extent of the damage. However, initial reports coming in from some vineyard areas suggest 40-80% of the vines potential crop has been affected. This is indeed catastrophic.
Factors which can influence the effect of frosting are the age of the vine, the type of soil and position of the vine. For example, vines placed mid-slope tend to be less susceptible than vines at the bottom of the slope (where the cold, heavy air tends to congregate).
What can be done to minimise the effects of frost?
In the northern hemisphere, continental climates tend to be more susceptible than maritime climates. So whilst Burgundy and Champagne are often badly affected at this time of year, Bordeaux and the Languedoc are rarely affected.
The Smudge Pot
In Chablis, northern Burgundy, they traditionally use two methods to combat frosting. Smudge pots or chaufferettes are little oil burners which can be placed besides the vines during impending frosts. These are inefficient and dirty, but they are able to warm the air above the vines just enough to prevent frosting. Although their use in Chablis is much rarer now, they were last used extensively throughout the vineyards in 1997. This is in part thanks to global warming.
This is another method commonly adopted in Chablis. It involves the use of sprinklers which spray fine jets of water into the air above the vines. These droplets fall onto the young buds and freeze. In so doing, the bud is kept at a constant 0 degrees centigrade – just enough to protect it from damage.
A large 15 hectare lake at Beines in Chablis was made in order to provide water for frost protection. However, again thanks to global warming, it is not often used.
Wind machines are a valuable tool for frost protection in areas where atmospheric temperature inversions occur. The warmer air inversion layer typically occurs at about 40-50ft above the vines. A wind machine standing at 30ft with 18-foot blades will mix the warmer air from the inversion with cooler air around the vines. One wind machine typically can provide 1-3°F of warming for about 10-12 acres of vineyard.
Wind machines are not often seen in the northern hemisphere, but are very much evident in places like Marlborough, New Zealand.
So how bad have the frosts of 2016 been?
Regions as widespread as Burgundy, Champagne, the Loire Valley and the Languedoc have been effected. On the 26/27 April, frosts in Burgundy have affected around 40% of the vineyard area from Chablis in the north to the Mâconnais in the south.
Christine Jacob of Domaine Lucien Jacob says it is too soon to estimate the full extent of the damage. However in some places like Beaune and Savigny-lès-Beaune up to 70% of the vines appear to have been badly damaged. The frosts have been described as the worst since the early 1980s.
The frosts have affected parts of Champagne up to 30% in places and the Loire Valley has been badly affected in the Touraine region.
Jean Luc Mary at Domaine de la Cune in the appellation of Saumur-Champigny said:
‘Yes it’s a reality in the Loire Valley, with lot of damage. But we observe some great differences inside the different appellations and regions. It’s worse in Saumur than Sancerre for example.
Each domaine can give its perception for himself. Here in the appellation of Saumur-Champigny, I think we lost 50 %. For Domaine de la Cune it is even worse – up to 80 % has been lost.
We wait 2-3 weeks more to see the development of the last buds after the first spring warmth, to see exactly inside each bud, if we have some bunches or not.’
Further to the west in the Anjou, they appear to have been luckier. Gilles Sorin at Domaine de la Motte stated:
‘For us we are lucky as the weather has been kinder. We have had no freeze, except in a small parcel where around 50% has been affected. Because we are on a slope, there hasn’t been a big problem. Elsewhere in Rochefort around 20% of the vines of my neighbours have been affected, it would seem’.
All in all, this appears to have been the worst spring weather in France for some decades, with many regions badly affected. By next week we will know exactly just how bad. However, Burgundy especially has been affected by summer hail in recent vintages and hence the yields have been much lower than average. Indeed between the 2012-2014 harvests, many producers have lost the equivalent of one year’s production due to hail. Another catastrophe such as this may well be the tipping point for many vineyards…