Bud Burst versus Frost (March – April)

Spring in the vineyards can be a stressful time here in France. From March into May is the time when, like many trees, the vines start to bud. Called bud burst in vineyard speak. But these sensitive buds are also very prone to frost. And some years are definitely worse than others.

Spring?

In the past, I personally wouldn’t have cared that spring had been tentative in coming. It might not have even registered in all honesty other than to complain it was a bit chilly. Since having managed a vineyard and gone on to grow my own food in my homestead garden, my goodness, I am noticing.

In general terms, spring starts where I live in France at end of January. It’s still chilly, there’s lots of rain, but there is progressive warmth in the air. Some years the progression to warmth is fairly smooth. Other years we are like a yo yo, first warm then suddenly cold. A warm sunny week or two here or there, only to be dashed when a particularly cold or rainy spell followed. Typically spring does not make up its mind until after April. And because of this, March and April are our most stressful months in a vineyard.

Frost?

Some years we suffer freezing night temperatures and frosts. Truly severe ones. Now again, why should most people care? I wouldn’t have in the past, but managing a vineyard certainly taught me to. Why, because these frosts mean the difference between having something to make wine from, or not.

In 2016, in the Chablis area, we lost probably a half or more of our potential grape crop to it. In 2017 we lost all of it. In the past France has had to declare an agricultural state of emergency due to the frosts. Many have lost entire crops, and not just grapes but other fruit crops as well. This goes on to affect quantity and prices. And this is something we all notice.

Bud Burst

You see, when we have those odd days of sun and warmth the dormant vines go into action.  They begin to sprout. The bud burst is really just that. The buds are not there and suddenly they are. True of much of the plant world really. I don’t know if the bud burst phrase is used as a general term or only amongst the wine makers. But it captures the concept extremely well.

These buds are going to go on to make leaves and fruit. When temperatures start to warm up the plants come out of their dormancy, sap rises and then little bits of green suddenly start showing up. These are the buds. And then phwaump! (That’s not a technical term.) The frost can suddenly hit and the buds, which have quite a bit of moisture in them, freeze. And die. So if they die, no fruit.

Protection

It is possible to protect plants, including vineyards, up to a point. Smaller fruit trees and other delicate plants may be covered by materials until the danger of frost passes. The trick is to not let the frost touch the newly forming buds. For the vineyards and other agricultural crops, the scale of size means covering with some form of plastic or fleece is really just not possible.

There are other methods, mostly very expensive. For the best vines, eg those that make the more expensive wines – think Grand Cru – some have in place water systems. Hoses run along the top of the vine wires. They spray mists of water and encase the plants in a thin layer of ice. Sort of surprisingly it really does protect plants from frost.

Most use a method to move the air. In flatter lands there is a sort of windmill thing. It has a burner below that you light with oil or wood. This heats the air around it and then as that warm air rises, the fan blows that warmed air outward about the vineyard. This is probably the best method, but again at quite a high cost. However, it is not a good resource on strongly sloped vineyards as warm air prefers to rise rather than slide down the hillside.

Hateful Smudge Pots

When we had our own vineyard in the Chablis area, a hilly area, what was was more typical was setting out smudge pots. Think 5 litre paint can with a substance that burns in it. They look like very large candles. They are placed at regular intervals up and down the rows of the vineyard (or orchards). The idea is to create warm air near the plants and keep the colder air above, and away from the delicate buds.

This is maybe the cheapest method in the short term. But they have a burn time, so eventually they are of no use. And have to be replaced year on year. Working with these is also labour intensive. You have to stay up all night to make certain the smudge pots stay lit, replacing when they are about to run out. Lose the warm air even a little and the cold air will descend on plants and your bud burst is busted.

What next?

How badly a frost affects the entire vine and its subsequent grapes is not always clear and won’t necessarily be known for quite a while. You do know there will be less grape production that year, just how much is lost remains at the mercy of additional frosts as well as the rest of this spring and summers weather.

If you wish to read more about The Frost and how it affected Burgundy, France in 2016 Wine Spectator wrote an insightful article and have a good picture to show the smudge pots. It’s a similar picture provided by Wine-Searcher for 2022. And this year? We never know. We just have to wait and watch. And when we enter the frost season, we check weather watches religiously, waking up in the early hours of the night regularly to check on our crops.

More about seasonal work in the vineyard:

If you would like to read more about what goes into making wine, check out the ‘What goes into Making Wine‘ section. This covers what is done in each season, and some more of the unexpected elements of this agricultural crop.

Winter is a very busy time : Winter in the Vineyard (November – February)

Dealing with budding vines : Spring in the Vineyard (April)

Shop Wine Lover Gifts

As wine makers, we are always on the search for interesting and unique and particularly French wine items for our vintage and antiques shop. Here’s a taste of some of the things we have found. Simply click on an image to see more: