Frost damage is a major source of anxiety for wine producers in European vineyards every spring. While grapevines can withstand cold temperatures down to -15 °C while they lie dormant in winter, early spring is the period when vines are at their most vulnerable. During this natural period of growth, tender, new buds, susceptible to frost damage are most likely to wither and brown. Discover the significance of land and environment on the production of Grande Charte Champagne.This article considers the different types of frost conditions, their effects and the measures wine producers can put in place to mitigate their impact on grapevines.
What are the different types of frost?
The two main types of weather conditions that are most damaging to grapes are Radiational frosts and Advective freeze. Their features are outlined below:
Radiational frost. This usually sets in on clear, still evenings and results in heat radiating away from the earth causing a dip in temperature in the air closest to the ground. Radiational frost typically happens when the night temperature is below 0 °C and the daytime temperature is above 0°C. Measures can be taken to mitigate the effects of radiational frost.
Advective freeze happens when a cold mass of air, often accompanied by wind and cloud blows into an area and takes the place of warmer air. Temperatures generally drop below 0 °C and stay there all day. Advective freeze is quite unpredictable and it’s more difficult to protect vines against its damaging effects.
Sometimes both conditions can occur in succession over a period of several days which can be devastating for vineyards. However, in general frost conditions are short lived and there are effective measures that you can take to reduce the damage.
How can you prevent frost damage in vineyards?
The most influential factor in frost damage is the vineyard location and the choice of grape variety. Later budding grapes fare better than earlier budding types. Follow the steps below to take preventative strategies:
- Choose the locations for the earlier budding grapes where the risks of frost are lowest.The cool air will always flow downhill, so positions in the middle of the vineyard slopes offer more protection against the cold.
- Ensure that there are no trees or bushes that prevent the air from flowing out of the vineyard either.
- Position vine rows in a way that enables air flow and hinders the cold air from settling in one area.
- Pruning. Strategic pruning is a simple and effective tactic for minimising frost damage. Well timed pruning can influence the grape budding date since unpruned vines will bud later. Double budding which involves early pruning followed by a final pruning once frost risks are lower or when buds are just beginning to break, can be effective.
- Soil moisture management. Wet soil retains heat and keeps low air warmer. Soil water content should be maximised a few days before a likely frost. Care should be taken to minimise erosion and loss of soil nutrients and organic matter too.
- Cover crop control.
Cover crops can stop soil from absorbing and retaining heat so they should be cut short before frosty periods.
What active measures can you take to prevent frost damage to vines?
The following section outlines the most common active methods to prevent frost damage in vineyards.
- Lighting candles or burning torches is a common method to protect the vines. When the candles are placed a few meters apart in the vineyard, they can increase the temperature by 2-3C which is enough to prevent frost from forming.
- Water. Spraying the vines with water can be an effective way of reducing frost damage. As the water freezes around the buds it actually forms a protective, icy cocoon which stops the moisture within the bud from freezing.
- Air turbines. Small turbines can be set up to promote air circulation and enable warmer air to prevent buds from freezing.
- Heated wires along the vines is becoming an increasingly effective and popular method of frost damage reduction on vines that are trellised. The wires can be programmed to come on when the temperature drops below a certain level.
- Helicopters are sometimes engaged in the frost reduction process. Low flying helicopters increase air circulation. This method is expensive and is usually only used in higher end vineyards.
Advancements in technology have meant weather forecasts are often more accurate which help winegrowers to take preventative measures. Overall wine growers are now better equipped to react quickly. However climate change has also brought about more severe weather conditions with which wine producers must contend.
Protecting grapes from frost damage is a delicate process which involves much dedication and several sleepless nights for vineyard workers. The journey of a grape from vineyard to glass involves dedication and countless decisions. So raise a glass to the winemakers next time you sip a delicious glass of wine!