Should frost nets be used more widely in vineyards?

This week, for the second year in a row, Bordeaux has been battling Spring frosts.

Temperatures dropped to -7C in the worst affected areas to the north of Castillon on the night of Sunday April 3, down to -5.7C in Lalande-de-Pomerol and -5C in Sauternes, with April 4 recording the coldest temperatures at this time of year since 1947. Winemakers have been out in force for three nights in a row spraying water, burning candles, oil drums and bales of hay, or trying to move the cool air by pumps, wind machines or even helicopters.

The full extent of the impact won’t be known for another few days or even weeks, as plots are assessed for damage to the young buds (there is even a national database that winemakers and others can use to upload observations and photos). The vines were less far along than with the devastating frosts of 2021 – not least because across Bordeaux estates have pushed their pruning schedule back as late as possible to try to miss the frost window, meaning that most of the buds were still ‘en coton’, the stage just before leaves appear, which gives some extra protection. This, together with the huge efforts across the region, means we can hope the final count will be less destructive than last year, even if remaining extremely significant for some.

But I wanted to share one winemaker’s story, because he was using a method to combat the frost that doesn’t get talked about much in Bordeaux, and yet seems to be an option that should be more widely considered.

This is Loic Pascquet, owner of Liber Pater in the Graves region of the Left Bank. Graves was one of the worst-impacted sectors in 2021, with final yields down by 38% compared to 2020, leaving many estates severely struggling to have any cash flow at all, particularly tough in a region that is dominated by small family-run properties without huge reserves of cash behind them. This year, Pasquet chose to employ frost nets that he used to cover 5ha of vines. He reported that the nets (which cost around €3,000 per hectare, compared to €6,000-€10,000/ha for frost candles, and are re-usable) raised the temperature from -5.2C outside, to -1C, with no damage to the young vines.

This is possible for Pasquet because he is no longer bottling under AOC Graves and has been using only Vin de France for his wines since 2014. It is in theory possible to use frost nets in Bordeaux within the AOC rules, if you ask for a dérogation under the terms of trial usage, with the resulting permission lasting for five years – but it takes time to get this, and is not assured. Frost nets are already being trialled in Chablis, with success – and I know of at least one well known winemaker in Pessac-Léognan who was using them this year on a trial basis.

‘In 18 years I have tried everything against frost,’ Pasquet said, ‘and this is the first time that I have had a 100% success. Nets work, without a doubt’.

The eternal question in the AOC regions of France is how to avoid using techniques that will have an impact on terroir expression – so no irrigation except in extreme circumstances, no using plastic sheeting to cover the soils in rain, no widespread use of hail nets and so on. But the climate is becoming so chaotic that winemakers need to be given more tools at their disposal, and nets clearly have far less environmental impact – the radio in Bordeaux this morning was full of complaints from people who were fed up with the smoke that lingered over the city this morning due to the number of anti-frost candles being burnt in the surrounding countryside. Light and rain can still penetrate the nets, they simply raise the temperature underneath (by up to 4C depending on external conditions) – surely using them for one or two nights a year is better than burning hundreds of litres of fuel for hours at a time?