How Vineyards Can Protect Their Grapes from Devastating Frosts  

windmills in grape farm

By: Alyssa L. Ochs

Various weather hazards put delicate wine grapes at risk, including hail, high winds, wildfires and droughts. Frost is another major issue in vineyards across the country, especially spring frosts that attack emerging shoots and buds when they are just beginning to form. The riskiest time, which requires strategic planning and advance preparation, is when bud break has occurred, but the frost risk has not yet passed.

  To address these cold-weather concerns and help vineyards protect their grapes from frost damage, industry experts weigh in to share their knowledge and provide guidance for a successful yield.

Types of Frost and the Risks

  Different kinds of frost can harm delicate grapevines depending on where a vineyard is located. Advection frosts occur when temperatures are below 32 degrees Fahrenheit, and the wind is greater than 10 miles per hour. This type of frost happens with a weather front moves into an area, and cold, dry air replaces warmer air. Radiation frosts are associated with temperatures above 32 degrees Fahrenheit and calm winds. These frosts occur during clear skies and due to lost heat as radiant energy.

  Both weather patterns are problematic for vineyard operators and influence whether active frost protection methods are effective. Frost is a significant issue for vineyards because of the dangers of uneven ripening, decreased fruit quality and damage to an entire vintage in severe cases. Frosts can happen unexpectedly during the growing season and when grapes are dormant. Meanwhile, some types of grapes are more susceptible to frost damage than others.

Overview of Frost Protection Methods

  Frost protection methods are typically divided into two categories: active and passive. Active methods involve intentionally modifying the energy and climate of grapevines through wind machines, heaters, sprinklers and other measures. Overhead impact sprinklers, water micro-sprayers and cold air drains are other active methods to prevent frost damage.

  In contrast, passive frost protection methods do not require energy input or adjust the climate, instead focusing on strategies like cultivar and site selection, which must be considered before establishing a vineyard. Other passive approaches include looking at soil water content, cover crops and barrier management. A combined strategy with active and passive measures is often most effective in the vineyard, especially alongside good vineyard design, vineyard floor management, sprayable products and late pruning if necessary.

Professional Help with Frost Protection

  Fortunately, equipment manufacturers and specialty companies are available to help vineyards address their frost protection concerns. Since 1967, Orchard-Rite, a family-owned business, has engineered and built wind machines with precision technology. With its headquarters surrounded by vineyards, orchards and farms in Yakima, Washington, Orchard-Rite operates one main manufacturing and assembly plant and has supplied an estimated majority of wind machines and frost fans in operation worldwide.

  Shawn Miller, who leads sales and dealer support for Orchard-Rite, told The Grapevine how wind machines are an effective tool for protecting various crops from the damaging effects of frost and critical temperatures worldwide.

  “During radiation cooling nights, wind machines pull down warmer air and ventilate the growing area to prevent the pooling of cold air,” Miller said. “Most importantly, they provide air movement across the plant surfaces, which prevents them from supercooling. Even with a weak inversion layer or on clear, cold nights, Orchard-Rite machines substantially reduce the chance of supercooling.”

  Orchard-Rite serves customers with wind machines that protect against frost throughout North America, South America, Africa, Europe, Australia and New Zealand. Miller said these regions have special seasons that benefit from Orchard-Rite’s wind machines. For example, these machines help protect blooms from critical temperatures and frost in the spring, and they aid in drying the clusters and canopy of excess moisture in the summer. He said they also protect critical autumn temperatures when more time is needed before harvesting and during winter months when temperatures have fallen to the point of damaging or killing the vine.     

  “What makes us unique, is that we manufacture many of our wind machine parts, verses buying off-the-shelf-parts,” Miller said. “This gives growers the confidence in the quality of our equipment. As for the market share, warranty, product support, research and development and dealer support, we are by far the leader in the world market. With over 39,000 Orchard-Rite wind machines sold throughout the world, we have the longest proven track record, providing the best value, highest performing, quality wind machines with a worldwide dealer network to support parts, service and sales.” 

In addition to the products that Orchard-Rite provides, Miller told The Grapevine that other sources for frost protection can be used for supplementary heat, such as irrigation micro-sprinklers and fuel-burning devices.

  “Additionally, when supplementary heating is used with the wind machines, this can improve results of your protection,” he said.

  Another company that helps vineyards get a handle on their frost prevention tactics is Vigneron Toy Store, a Sutherland, Virginia-based business with products and services to assist vineyards with harvesting, spraying, canopy management, floor management, pre-pruning, leaf removal and frost mitigation. Kirk Thibault from Vigneron Toy Store told The Grapevine Magazine about how his company’s AgroFrost frost protection equipment is based on sublimation. He explained that this phase change of the water vapor releases energy into the bud and protects the crop from frost damage. He said these machines could protect with or without a thermal inversion down to 23 degrees Fahrenheit. 

  “AgroFrost machines are now in use throughout the world,” said Thibault. “They started in European orchards and have been protecting grapes, blueberries, apples and pears for many years. The tow-behind Frostbusters and stationary Frostguards are mobile and can adjust to changing conditions or changes to the vineyard. We have several differently sized units that can concentrate on individual blocks or entire fields depending on a growers needs.”

  Thibault told The Grapevine Magazine that something that makes this frost prevention solution unique is the fact that AgroFrost machines will recover your cost in one year’s potential fruit loss. 

  “No matter the weather conditions, our system works,” Thibault said. “Labor and start-up costs are far less than other systems, as one machine and operator can cover 15 to 20 acres and no further infrastructure is needed to operate the machine. At Vigneron Toy Store, we train you on every aspect of the machine and all operating procedures.”

Beyond the offerings at Vigneron Toy Store, Thibault said that promoting the vineyards’ natural environment to prevent frost is a helpful start.

  “Keeping grass short with bare ground under the vines helps return more ground heat to the vines,” he said. “It also allows better flow of warmer air across the vineyard. Wind machines and sprinkler systems also provide frost protection but require much higher infrastructure costs and can damage crops as well.”

  H.F. Hauff Company, Inc., based in Yakima, Washington manufactures the Chinook wind machine, which is popular among vineyards because one machine will cover up to 18 acres in a vineyard – 150 feet more than other competitive units. Dean Hauff from H.F. Hauff Company told The Grapevine Magazine that this product’s exclusive trailing edge wedge increases sector angle coverage to 80 degrees – a full 60 seconds of direction protection in the horizontal plane. He said warmer temperatures pull from higher up in the atmosphere in the vertical plane, raising temperatures more quickly on the vineyard floor. Another benefit he shared about the Chinook wind machine is its one-piece fan blade design, as air movement from the air foil starts 14 inches from the fan hub center with increased air movement directly under the fan. It’s also easy on fuel consumption (13.5 gallons of propane per hour or six gallons of diesel per hour), is competitively priced and comes standard with auto-start capabilities and a stainless-steel engine hood.

  “We are a conservative, family-owned business and have been in the agricultural manufacturing business for 58 years – 54 years directly involved in wind machines for frost protection,” Hauff said. “We were trained by the originators of the first wind machines and have grown up with the evolution of the wind machine from the ground up. Our quality manufacturing process is based on sound engineering principles and aerodynamics dedicated to our customer needs.”

  In addition to the Chinook wind machine, Hauff said that horticultural practices are an important tool in any overall frost protection strategy.

  “Besides wind machines, low emitter sprinklers work well,” Hauff said. “From grass to dry dirt, you can pick up one to two degrees, from dry dirt to wet dirt another one to two degrees. If possible, planting your vineyard rows with the natural drift will help by giving extended time before the cold air drain begins to back up. Also, planting on the higher ground will aid in delaying the frost. Frost is a lot like water because it flows to the low ground first and then begins to back up to the higher ground, freezing out the crop as it goes.”

Frost Strategy Management and Tips

  Many vineyard owners and managers are turning to high-tech solutions like weather stations, data monitoring and flow meters to manage frost protection in the vineyard. Yet some instances of frost damage are inevitable despite all the latest innovations. Therefore, it is vital to know the steps to manage the damage, including assessing injury to grapes after a frost and deciding whether to remove damaged parts of the plants or allow them to remain intact.

  Miller from Orchard-Rite offered some advice for vineyards looking to improve their frost prevention strategies this year.

  “It is very important not to wait until you are at a critical temperature to start your wind machine,” Miller said. “We recommend that if the forecast conditions are going to reach critical temperatures, farmers should start their wind machines three to four degrees Fahrenheit above the critical temperature for the crop being protected. Additionally, make sure that you have opened areas up that can trap or dam the cold air, such as fence lines full of debris.”

  Thibault from Vigneron Toy Store recommends determining the vineyard’s coldest area or most frost-sensitive variety and placing a Frost Alarm at the fruit level.

  “Our Frost Alarms provide cell phone warnings based on wet temperatures for the temperature you set,” Thibault said. “Frost doesn’t always happen at 32 degrees but can occur at 34 or 35 degrees sometimes. You should start to protect your vineyard slightly before the damage temperature. The most common mistake we see people make with any frost protection system is starting after damage has already happened.”

  Finally, Hauff from H.F. Hauff Company advised that those with no frost protection in place should seriously consider putting in a wind machine.

  “It is less labor-intensive than other options, operating costs are low and unit coverage can be great,” Hauff said. “In addition, a wind machine will keep on protecting your crop year after year.”

  For those with wind machines in place already, he said they should look at improving the efficiency of the systems currently in place. 

  “Upgrading your current wind machine is not out of the ordinary,” Hauff said. “Not all fan props are created equal. Many improvements have been made with regard to technological breakthroughs, aerodynamics, increased horsepower and increased performance. In the 1940’s, six to eight acres was the standard fan coverage. Today, the advanced aerodynamic features of the Chinook fan prop protect a full 15 to 18 acres. Matching your current fan and engine horsepower and replacing it with a properly sized Chinook fan will improve your fan coverage by roughly more two acres.”

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