During the first few days of May (particularly on the 4th overnight), the Moselle suffered a cold snap. Temperatures fell below zero early in the morning causing extensive damage, and to vineyards not usually hit by late frosts, such as the Hommelsberg in Wintrange. The organic winemaker Yves Sunnen (Domaine Sunnen-Hoffmann in Remerschen) explains what happened.
What was the damage done to your Hommelsberg vines, in Wintrange, an area that was particularly hit by the frost?
Yves Sunnen: In Wintrange, I’ve lost around 60% of the crop and on the Hommelsberg, it’s far worse. Up above below the forest, 70% of the vines suffered frost damage and below, in the valley, at least 90 to 95% of the vines are useless. It may even be 100%. Overall, of my 9.5 hectares, five have suffered severe frost damage. The Hiischeberg, in Remerschen, was also particularly affected.
Over recent years, the Moselle has often been hit by frost, but three times in four years, that’s a lot!
Yes, we had frosts in 2016, 2017 and 2019. This year has been by far the worst. Fortunately, 2018 was a generous year, a gift of nature. Now, it’s clear that we’re no longer accustomed to getting these late frosts. The last one to cause significant damage was in 1991.
So are we right to name again those early days in May the Saints de Glace (Ice Saints)?
It’s not for nothing that they are famed for frost! The problem lies with global warming. Before, vine growth took place in May, but now it’s in April and it was very hot over Easter. Since the vines are growing quicker and earlier, frost can appear at critical times such as when the buds are bursting. That’s what happened this year. And if there are no buds, well there won’t be any fruit…
At the end of the night, the moisture froze on the leaves and when the sun rose, the ice acted like a magnifying glass burning the leaves.
Yet, it wasn’t terribly cold in May…
No, but the temperature needs only to drop to -2°C or -3°C. On the Hommelsberg, the cold air was trapped down in the valley [which ends in a cul-de-sac] and it was very damp. At the end of the night, the moisture froze on the leaves and when the sun rose, the ice acted like a magnifying glass burning the leaves. When the sunlight is concentrated this way, the impact can be extremely powerful: a magnifying glass is a great way to light a fire. So it’s not necessarily a question of temperature. When all the factors are combined, it doesn’t have to be very cold.
Are there ways of protecting the vines that work? In Burgundy, they light fires to heat the air…
In Luxembourg, we’re not allowed to light fires in vineyards as it’s forbidden by the Ministry of the Environment. Having said this, if we were to ask, perhaps we could be exempted. However, the problem is that we never know in advance which vines are actually going to suffer from the frost. Those which were damaged this year were up until now the ones generally considered to be protected! If I had had to put equipment in place to fight the frost, I most certainly would not have chosen the Hommelsberg, for example; instead I’d have gone close to the football pitch in Remerschen, in the bottom of the valley, a place where there’s often frost. However, this year, the fog remained for longer in the bottom of the valley, protecting the vines from the morning sunlight. We’d need a huge number of volunteers to light fires and help us protect everything and we just don’t have them. Anyway, these extreme weather phenomena which have become increasingly common over recent years are totally unpredictable.
In certain regions, particularly in Germany, fans or even helicopters are used to create air movement and prevent pockets of cold air collecting near the ground – can you imagine this happening here?
I doubt that the helicopters used for spraying would be effective enough for that… Perhaps you’d need larger ones… As for using fans, once again, I would never have put them up on the Hommelsberg, as this terroir isn’t usually susceptible to frost. I think you have to be quite fatalistic – we’re dealing with nature here. Fortunately, we are well insured against frost and hail [the State provides 65% subsidies, the maximum permitted by Europe]. However, this money doesn’t fill our cellars…
The vines have to gather their strength. They are plants, a living organism and not just wood and fruit.
In the vineyards, a very clear division is visible between those vines that suffered frost damage and those that didn’t. How will the vinestocks react, now?
There are several possible scenarios. If the flowers are black, there’s no hope. We’ll then have to see whether the wood will grow back enough to support next year’s growth. If the tip guiding the shoot is burnt, you can be certain of nothing… The greater the number of young shoots burnt, the more serious the repercussions. Under these circumstances, since you can already more or less draw a line under this year’s harvest, you’ve got to start thinking ahead already to the following harvests. Your work revolves now entirely around getting the vines back into shape. If the top of the vinestock [the place from where the previous year’s shoots appear, those which will bear the grapes] is too damaged, we can cut it back and start further down.
So this year’s frost could also have an impact on the 2020 harvest?
Yes! It takes two years for a grape to grow. When the vines were hit by the frost, they were also busy making a start on the 2020 crop. So there’s a real risk that next year’s harvest will be small because of this episode. To have a frost as extensive as this injures the plant, it’s in shock. A few weeks later, the vines are still in a sort of coma: they aren’t growing at all. They are convalescing, just as you would after a car accident. The vines have to gather their strength. They are plants, a living organism and not just wood and fruit. To help them recuperate, I sprayed them with valerian.
The result is that you’re even going to have to put a lot of work into those vines that have been completely damaged by frost…
They’ll take even more work! For example, the dead leaves provide the perfect environment for diseases to develop. So we’ll have to carry out phytosanitary protection. Vines that have suffered frost damage are fragile because they’ve been weakened as has their capacity to resist disease. Once the leaves start growing again, the stocks are very vulnerable so we’ll have to take great care of them…