Having worked with growers for half a century, we understand that spring frosts are one of the worst threats vineyard owners face.

While you can argue that the best way to prevent damage is to ensure the right varieties of vines are planted on frost-free sites, frost is something the majority of growers in the UK have to deal with at some point. Especially as we are seeing more advection, or wind frost, events occurring on a global scale during flowering.

Both radiation and advection types of frost may occur during a frost event, and growers should also be aware that the temperature, humidity, topography and soil moisture all significantly impact how much damage is caused to buds.

The amount of weeds and length of grass also have a big impact on the efficacy of whatever frost protection you have in place.

One of the oldest methods of protecting vines is heating the vineyard’s air. Many UK growers have adopted the traditional French practice of placing and lighting bougies.

This “tried and tested” method has been used for years, but as effective as they are, they do require a significant amount of labour to set them out, light them (often during the small hours of the night) and bring them back in.

Those looking for a more efficient approach have long chosen to use the Frostbuster and Frostguards from Agrofrost.

Unlike other frost protection systems, the working principle is not based on raising the temperature above the critical values but on phase transition and controlling the formation of hoarfrost, which is the biggest enemy of flowers and buds.

The phase transformation of vapour into hoarfrost is called desublimation or deposition and liberates a lot of energy. This energy is transferred to the surrounding air and soft tissue of the vine.

Without protection, the layer of hoarfrost will increase and finally cause damage to the plant by dehydration as the ice crystals extract energy and humidity from the buds and flowers.

The Frostbuster and Frostguards we supply allow growers to protect crops at sites where no water is available and can be used not only during radiation frost but also during wind frost.

Both machines form a hot air stream every seven to 10 minutes, so part of the ice evaporates while the remaining ice gets energy from the passing air. The higher the humidity, the more energy is transferred. This allows growers to protect crops with only a fraction of the energy input that other systems need.

The Frostbuster works by burning gas to provide a heated air supply, which is then blown by a tractor-driven fan. Driving around the vineyard following a pre-determined route makes it possible to protect an area of up to eight hectares.

Alternatively, the Frostguard is a smaller, stationary version of the Frostbuster, featuring a petrol engine-powered fan that can rotate 360° continuously to protect up to one hectare of vines.

Both machines have been scientifically proven to offer protection in radiation frosts down to -5.5°C and down to -3.5°C with a wind frost. Lower protection temperatures are possible, but for every degree below -5.5, the protected surface is reduced by about 10%.

Growers will often opt to have several Frostguards located in known vineyard frost pockets rather than having to drive a Frostbuster around in the night. The area protected will also depend on the direction of the wind and will need to be evaluated each night to ensure the right area is being protected.

In a previous edition of Vineyard Magazine, Romain Henrion, from Hattingley Valley Vineyard, commented: “I wanted to tell you about the excellent results regarding the Frostguards. This year and last year, we had several cold spells in the spring, and the Frostguards have shown great efficiency on our sites. We were able to reduce the damage to <1% on the total plots, which represents a minimal economic loss for us.”

WineGB members looking for an in-depth review of a range of frost protection methods, along with temperature monitoring systems, can visit the knowledge section in the members-only area of the website.

If you would like more details about the Frostguards and Frostbusters from Agrofrost, as well as the other frost protection equipment we have in stock for the 2024 season, please phone us on 01580 712200 or email sales@npseymour.co.uk