Cold comfort: finding the right frost protection mix

Wines & Vines, Sept, 2003 by Tina Caputo

In early April, five consecutive nights of frost wreaked deadly havoc on the vineyards of Champagne. The Comite Interprofessionel du Vin de Champagne (CIVC) estimated that 80% of the region's Chardonnay buds were lost, and Champagne houses like Clicquot and Taittinger reported significant losses.

Cooler wine regions like Champagne aren't the only ones susceptible to frost damage. Nearly all of the world's winegrowing regions can be affected by frost--including "sunny California." That's why it's crucial for wineries to take the right frost protection measures, whether that means planting vineyards in frost-resistant areas or installing wind machines.

There are two categories of frost protection: passive and active. Passive methods include things like site selection (i.e. planting on slopes so the denser cold air Can drain away from the crop), variety selection (planting frost-resistant varietals) and limiting cover crops so the soil can absorb more heat. Active protection methods employ the use of heaters, wind machines, helicopters, foggers or sprinklers.

Though active methods are said to be more effective than passive ones, they are also more costly. Rather than choosing one or the other, most U.S. wineries use a combination of passive and active frost protection methods.

Frost In California

California is home to multiple climates and types of terrain, which require individualized frost prevention programs.

For Ted Edwards, director of winemaking at Freemark Abbey in St. Helena, keeping frost away is a minor, but necessary, concern. "Freemark's source vineyards are located in the Rutherford appellation on the valley floor, next to the river," he said. "We do experience a few days of frost every year--we use a solid-state protection system, which is basically sprinklers. However, our vineyard-designated land, Bosche and Sycamore Vineyards, is not protected because it's on the Rutherford Bench, which provides a little elevation and slope for the natural wind currents to flow through."

Winemaker Daniel Baron, of Napa Valley's Twomey Cellars, combats frost with the help of sprinklers and wind machines. "Frost protection is only an issue where it was not installed on one vineyard that we purchased," Baron said. "This was because it had never had any frost damage since being planted in the mid-'90s. There really weren't any killing frosts during that period, so when we got one in April of 2001, we lost crop in the low spots. Consequently, that ranch now has wind machines and a small block of sprinkler protection. All our vineyards, except one mountain vineyard, are susceptible to frost."

Craig Raymond, vineyard manager for Raymond Vineyards in St. Helena, said that frost protection is sometimes necessary, though not as often as in previous years. "As a child I can remember seeing sprinkler ice hanging on the vines many cold mornings each spring," he said. "In the last 20 or so years, however, the incidence of cold temperatures has decreased to the point where I only run our system one or two times a year. Even then, temperatures have never been so cold as to absolutely require frost protection at our location. There has definitely been a warming trend over recent decades, to the point where even the need for a frost protection system is questionable. Whether this is due to global warming or just normal earth cycles I'll leave to others to debate. Depending on the location, many growers currently get away with no frost control at all."

Despite the warming trend, Raymond said, frost protection is sometimes necessary. "In Napa County, the only location at which we use frost control measures is at our winery south of St. Helena. Seventy-five acres at that location are protected with overhead sprinklers, the operation of which I am personally responsible for. Still, in a low or cold area, there is too much investment on the line to not be protected in some way. Most of the time this means a wind machine, and if you live here you can only hope that there is not one in a vineyard close to your house. They are quite noisy and it seems to me that growers love to run them if temperatures get anywhere near freezing. In fact, I'll go on record that I believe more than 50% of wind machine operation is completely unnecessary. Please, would all growers go buy mufflers for their damned wind machines?"

Bob Pecota of Robert Pecota Winery in Calistoga also said he has had fewer problems with frost lately. "Fortunately, we have not had any serious frost in recent years, but it is always a worry in Calistoga," he said.

Pecota uses a combination of active and passive methods to combat frost. "We use gas-powered wind machines, with each covering about eight acres. Other measures include late pruning, which delays bud-break in, the spring, and chopping of winter grasses to allow for air circulation. We likely average about $2,000 a year on direct costs for frost control on 40 acres."

Beyond Napa Valley

"In Monterey, frost has never been a problem," said winemaker Jeff Meier of J. Lohr Winery. "However, frost protection is necessary in the winery's lower-elevation vineyards. Only about 50 acres are frost protected there, Proximity to the bay helps keep frost away, and the vineyards are located on a plateau that is three to five degrees warmer than the surrounding areas. In Paso Robles, there is one vineyard that has a lower elevation--Pleasant Valley--where colder air can pool, so that vineyard is frost protected."