Tuesday, April 24, 2012

Protecting Our New Buds from Frost

Spring is such a wonderful time of year; a time when we all feel a sense of renewal, at least until Daylight Savings comes and then we all just feel tired. As wonderful as it is to feel the warm breeze after some long, cold, (and usually wet) winter months, spring can be a very stressful time around here thanks to the looming threat of frost.
Frost… a word that strikes fear in the heart of every farmer. Without getting too technical (because I went to culinary school therefore I can’t be too technical) the temperature drops causing ice to form in the plant’s cells which causes them to burst, killing the bud. These new born buds are very susceptible to frost damage because they are made up of very young tissue. In fact new vines can also be damaged by heavy frost because they have yet to build their own natural insulation.

There are, however, a few methods farmers (or if you want to use the fancy term, viticulturists) have found useful for protecting our future bottles of wine.

Wind Machines
A very common method in Napa Valley is air mixing with wind machines (they look like airplane propellers mounted on top of sticks, actually some look like old plane engines). One huge drawback is they are very loud, imagine a helicopter landing on your house, but they do a good job. Once the temps drop to just above freezing the fans are turned on (by some very unlucky individual as it happens in the wee hours of the morning) and the cold air is mixed with warmer air raising the temperature and inhibiting the formation of frost. If you have a property that isn’t affected by frost very often you can hire a helicopter to buzz your vineyard all night, it will have the same effect, although I am not totally sure that is kosher in Napa County.
Another method used is overhead sprinkler systems. I know that seems a bit strange, if is cold enough to freeze how is water going to help? Amazingly it does! Think about a glass of ice water. Even though there is ice in there the water never gets colder than 32 degrees. As long as there is a constant flow of water the buds will be okay, but it does take a lot of water, about 50 gallons a minute per acre. A winery needs large water reserves for this method.
Smudge Pots

Although their use was restricted in the 1970s smudge pots were once a very popular method of frost protection. The large iron pots were placed in the vineyard and filled with fuel oil and ignited once the temperature dropped. The heat from the fire would keep frost from forming. They were restricted (not banned) because of air pollution concerns and also fell out of favor as fuel prices increased, but are still used by a few wineries in Napa.
Those are the main active methods of frost prevention, there are also passive methods such as soil management, trellis height, delayed pruning, protective covering, or most importantly picking the correct site for a vineyard. Using a combination of active and passive methods will help those little buds, but no matter what we do frost season will always be a stressful time around here.

Rebecca Martin, Chase Cellars

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