What Happens to Vineyards in Bordeaux Over Winter?

Bordeaux has long and proud history that spans more than 2,000 years. It is considered the most famous wine region in the world. Home to over 8,000 châteaux that make wines along with 13,000 wine growers, over sixty different appellations, and sixty-one grand cru Classés. it is the largest fine wine producing region on earth and produces about six million hectolitres of wine annually. 

Wines were made by the Romans brough the first vines to the region in 43 A.D. Learn the entire history on one of Bordeaux Wine Pilgrims Bordeaux Wine Tasting Tours.

Climate and Overview of Bordeaux

The vineyards of Bordeaux grow on the 45^th parallel which means that they at the halfway point between the Equator and the North Pole. (the same as the vineyards of the Northern Rhône Valley). Bordeaux enjoys a temperate Mediterranean climate with an average temperature of 13°C. The climate is marginal at best, and metrological conditions change from one growing season to the next, creating a large variation in the growing conditions for each vintage as achieving fully ripened grapes is dependent on the temperature and weather conditions.

Bordeaux wine country is divided into two main parts – the Left Bank and the Right Bank and are separated by the Gironde Estuary and the Gironde and Dordogne Rivers.

Bordeaux’s Left Bank is bordered by the Atlantic Ocean to the west and the Gironde River to the east, and many of the finest Châteaux in Bordeaux are found here and Cabernet Sauvignon reigns supreme.  The terroir is primarily composed of alluvial gravel with limestone underneath, though some areas feature large deposits of clay. The well-drained soils combat the maritime climate which provides warm temperatures that promote the ripening of the grapes during the summer months. The wines are known for having big tannins and a structure that requires more aging than their Right Bank neighbours.

The Right Bank is bordered by the Dordogne River to the west with a terroir that is dominated by clay that retains water, perfect for growing the grapes for its famous Merlot-based blends.  The  young wines are smooth and supple with tannins that are mellow and accompanied by soft fruit and can be enjoyed young though many of the upper tier wines will improve with extended ageing.

More than 90% of the wine produced in Bordeaux is dry red wine. Notable dry white wines are made predominantly in Entre-deux-Mers, Graves, and Pessac-Léognan, and the legendary sweet wines of Bordeaux are made in the Left Bank in Barsac, Sauternes, and Cadillac in the Entre-deux-Mers area. There is also a limited production of sparkling wines made using the traditional method, and some rosé wines.

The Secret to Making Great Wine Is a Strong Vine

In Bordeaux, there is an average of 10,000 vines planted per hectare. The soils are extremely poor and there is a limited supply of water (an average of 900mm of rainfall annually) which means that vines must compete with each other for the much-needed nutrients and water that is essential for them to survive and grow strong.  Viticulturists create “vine stress “which means that the vines must push their roots deep into the soil and produce a smaller vine canopy in the summer.  As a result grapes will still ripen sufficiently even if the weather conditions are not ideal.  Since the vines struggle to survive, this also limits their grape production resulting in more concentrated but smaller quantities of grapes – the secret to producing wines that are not only good but exceptional. Another benefit of the long deep roots that can grow as long as six metres is that it helps to protect the plants during the cold winter season as they are far below the freezing temperatures on the soil surface which lowers their rate of mortality.

The Winter Cycle in A Bordeaux Vineyard

Winter in the Bordeaux begins in November and extends to the end of March. This is a very important time for viticulturists, as this period is spent preparing the vines and vineyards for the next growing season and vintage.  It is essential that the vines are carefully monitored and cared for to ensure that they will be in optimal condition when the new growing season starts. Contrary to popular belief, the winter is a very busy period in the vineyards as the vines must be prepared for following season and the subsequent vintage that will be produced.

What Happens When Vines Go Dormant?

Once the harvest is complete, usually around the end of September though sometimes extending into October, the vineyards begin their transformation as the days become shorter and the temperatures begin to grow cooler.

The period of dormancy is a crucial part of the vines yearly life cycle and provides a much-needed rest period so that the vine can recover from the long growing season. The vine regenerates which will ensure its continued good health and sufficient energy levels to continue producing excellent grapes the following season to create another great vintage.

The vines no longer require their leaves for photosynthesis and as the autumn chill arrives in the vineyards, the leaves will change colour and eventually fall off.

The vine reduces its metabolism by stopping the growth of new shoots and branch growth to further conserve its energy.

The vines then accumulate their energy reserves such as carbohydrates and other essential nutrients needed for their growth in the next year. These resources are sent to parts of the vine such as the roots and lower trunk that are protected during the cold winter months. Though the top of the vine is asleep, the roots are busy taking in all energy that they can from the soil and are growing strong and robust in preparation for the next growing season.

The vine adapts to the winter cold through physiological and biological adaptation of its cell structure such as the reduction of water in the plant and the concentration of solutes in the vine cells.
At the end of the winter the vines will come out of dormancy. This is determined by the temperature. Warmer weather makes the vine commence with its preparations for budburst. This is a very vital stage in the life of the grapevine as it will determine how uniform the budburst will be for the new growing season and the quality of the following harvest.

The Great Freeze Of 1956

Some grape varietals are more resistant to frost than others, and viticulturists and winemakers do everything that they can to protect their vineyards during the cold months. However climate change is beginning create more irregular weather patterns which can either mean that the weather will be warmer than usual which can bring the vines out of dormancy sooner than they should, or also very cold weather and late frosts that can be devasting and destroy entire vineyards and the future harvest. This makes the springtime a much more risky in the vineyard. There have been several serious frosts over the past several decades, however none of them were as bad as the calamity that stuck Bordeaux on 21 February 1956. The weather had started to become warmer and the vines thinking it was spring started to come out of dormancy. Suddenly the temperature made a radical shift with heavy snowfall and temperatures that plummeted to -25°C. The sap that has risen in the vines froze, killing them, destroying massive portions of the vineyards on both the Right and Left Banks.
The grape varietal that was worst hit was Malbec, and 75% of the vineyards were completely decimated. There was a positive outcome despite the almost complete loss of the 1956 harvest – the vineyards were replanted with varietals that were more resistant to frost such as Cabernet Franc and Cabernet Sauvignon. Though Merlot is not so resistant to frost, it still does make up the majority of red vines in Bordeaux’s Right Bank vineyards due to the rich exceptional wines that it produces. Before 1956, 60% of Bordeaux’s vineyards were planted in white grape varietals, this number has now dropped to 8%.

Primary Grape Varietals in Bordeaux

Bordeaux is famous for its blended wines and currently thirteen different grape varietals may be cultivated made into the wines of the 65 appellations that produced in Bordeaux.

Red Varieties:

Merlot is the most planted red grape varietal accounting for 66% of all red vines that are planted. Cabernet Sauvignon is the second most planted red grape varietal and account for 22.5% of red vines that are planted. With Cabernet Franc accounting for 9.5%. There is three secondary varietals (2%) Petit Verdot, Carménère, and Malbec and are often used in small quantities in different red wine blends.

White Varieties:

Sémillon accounts for 45% of all white vine plantings, followed by Sauvignon Blanc at 43% and in third place Muscadelle at 5%. The remaining 7% of white vines is made up of four secondary varietals that are Merlot Blanc, Colombard, Sauvignon Gris, and Ugni Blanc.

In 2021, four other red grape varietals, Arinarnoa, Castets, Marselan, and Touriga Nacional as well as two white grapes Liliorila and Alvarinho have been approved for cultivation to ensure that Bordeaux can continue to adapt to climate change.

Winter Vineyard Tasks

Once the final has finally gone into dormancy, the vineyards become a hive of activity. While the past vintage is ageing in the cellars, the winery teams are out in the cold vineyards busy conducting the many activities that need to be conducted in the vineyard to prepare for the new growing season.

Vine Pruning

Pruning the vines over the winter months is one of the most important tasks and must be completed whilst the vines are dormant. The is one of the only times during the yearly lifecycle of a vine that the winemaker and viticulturist can have an influence on outcome of the next seasons harvest. Vine pruning is a long and arduous task that is carried out in often freezing and wet conditions.  Each plant is individually inspected and carefully pruned by hand which means that it can be very time consuming and costly depending on how many workers are needed to prune the vineyards of a château.  This is a very precise and time-consuming process, and every single vine must be pruned to exacting standards. A well-trained pruner can prune up to seven hundred vines per day with manual secateurs and up to 1500 if an electric version is used.  Each cut must be made in the correct spot, and pruners must be careful not to break the shoots that they have pruned. 

In Bordeaux, depending on the number of hectares that a château owns, the pruning may start as soon at the vines go into dormancy November and it must be completed before the vines begin to wake up towards the end of March. With an average of 10,000 vines per hectare the larger estates need to get out into the vineyards as soon as they can as the process will take several months to complete. Smaller estates have the flexibility as to when they can begin pruning their vines. Up to 90% of the old shoots are removed, however each plant must be evaluated and then the pruner will decide which shoots should be kept for the new growing season and even the growing season after that, if you join one of our bordeaux wine tasting tours you will have the opptunity to meet the winemakers first hand and learn mire in depth on this topic.

 Repairs in the Bordeaux Vineyard

• Workers will check the integrity of the trellises, stakes, and wires in vine rows and make any repairs that are required. Drainage systems will also be checked to ensure that they are functioning properly. Winter rain is common in Bordeaux, and it is important to ensure that the water drains away properly to ensure that the vine roots do not become waterlogged.
• The soil may be tilled, and viticulturists may then opt to plant a cover crop that can help to prevent erosion and improve the health of the soil as well as help control unwanted weeds.  Vines will also be inspected to see if they have any diseases and pest control may also be conducted by organic or physical methods.

• Wildlife and Ecosystem Management: Many Bordelais viticulturists use sustainable, Haute Valeur-Environnmentale (HVE), organic, and biodynamic methods of viticulture. By creating and maintaining suitable habitats that will foster a balance between the local wildlife and the vineyard, the biodiversity is improved which can help to naturally control vineyards pests and diseases.
• Replanting Grape Vines viticulturists will make an evaluation at the end of the winter season usually at the end of February or in early March to determine whether any vines have died or been so severely damaged that they must be replaced. Once the soil has thawed and is cultivatable, the old vines will be uprooted and replaced with new vines.

Ways to Protect Vines From The Cold

Although severe winter frosts are rare in Bordeaux, preparations like mounding soil around vine bases (hilling-up) can protect vines from freezing temperatures.

Protecting the vines during the cold weather of winter begins in the summer and no fertilizer or nitrogen-rich products are added to the soil after June so that the vines will become deprived of nutrients and go into hibernation during the winter.

Many viticulturists will use cover crops to remove excess nitrogen. Cover crops also help to use up excess water and help to prevent erosion as well as creating biodiversity within the vineyards.

the vine stem above the graft and cover it with several centimetres of soil. The graft is one of the most delicate parts of the vine and is particularly susceptible to damage during cold winters. By covering the trunk of the vine above the graft with several centimetres of soil is a good way to insulate these fragile parts of the vine and offer protection from freezing.  Even if the rest of the plant is destroyed, the protected parts under the soil can survive and though they may not produce grapes for the coming harvest, it does mean that the vine does not have to be replanted which is time consuming and also costly because young vines must grow for three years before they begin producing grapes.

Welcome Spring - How Can Vines Be Protected from Frost?

During our Bordeaux Wine Tasting tours in early April you will see the entire Bordeaux vineyards covered with smudge pots.

Weather events like the devastating effects of the 1956 freeze can destroy an entire wine region and the weather is the viticulturists biggest enemy. What can be done to protect the developing vines and from damage once they have come out of dormancy?

At the end of February as temperature begin to rise, the vines slowly begin to awaken form their long sleep. The sap slowly rises from the roots of the vine and moves up to the furthest extremities of the canes that have been pruned. The sap creates droplets on the cuts and are called “vine tears” and heralds the beginning of a new growing season.

Now that the vines have come out of dormancy, this is a very critical and often stressful time for viticulturists as the temperature and weather conditions can be very unstable and the vines are at heightened risk of damage from late frosts. As the weather grows warmer the vineyard buds that are covered with a downy cotton like protective covering that will swell up and then burst (budbreak). This a very precarious stage of the growing cycle the temperatures can still drop below 0°C right up until the 10^th of May – Saints de Glaces – (day of the Ice Saints) and viticulturists have  carefully monitor the change in temperature so that they do not lose their harvest before it has even begun to develop.

There are different preventative measures that can be implemented to reduce the damage of frost:

• One of the most common ways of keeping the vines and developing buds warm is by burning bales of hay which create a protective blanket of smoke that is warm and heats of the air around the vines, it is essential place the bales correctly so that the warm blows onto the vines.
• Candles can be used and around three hundred are needed per hectare, but they last for up to twelve hours so can be used for two nights but they must all be lit every evening and blown out in the morning.
• Air heaters are another option and can either be installed permanently in one place or also come in a portable version that can be moved around.
• Water can be sprinkled on the vines using an irrigation system. The water freezes around the buds and vine leaves and protects them in a little frozen bubble until the weather warms again.
• Valerian is used by biodynamic grape growers as apparently is gives the vines more strength to survive the cold temperatures.
• Most costly options include Aeolian wind turbines and fans that are either permanently installed or can be moved around and keep the air circulating instead of settling. Electrical Cables are a very costly option and are sometimes used in Southern England and Cognac to keep the vines warm. For €1600.00 per hour, helicopters can push the frigid air up from the earth and can protect an area of around ten hectares and can fly from 6 am the coldest part of the day.

Conclusion

Though we may associate the growing season as being the time that the most activity takes place in the vineyard, that is far from the truth. The cold winter months in Bordeaux or any vineyard are vital to ensure that the next years harvest will be a success.  The increasing variations in the climate have created more chances of inclement weather such as late frosts, hailstorms, or other weather catastrophes that viticulturists and winemakers must try to combat. Through adaptation, the Bordeaux wine industry is continually working to improve how vines are protected throughout the winter ensuring that there will be another successful vintage in the new year. BordeauxWinePilgrim hopes to see you on one of our many vineyard and Bordeaux Wine Tasting tours soon.