Another Wine Word: Frost Protection!


Springtime visitors to Napa Valley have been known to call the cops in the middle of the night to complain about low-flying aircraft near their hotel. I wonder how many calls the county gets per season… 

I’ll bet it happened several times over this past weekend because both Friday and Saturday nights I heard the unmistakable hum (unmistakable once you know what it is) of wind machines.  

What this means is that some poor vineyard manager had to get up in the wee hours (I heard the hum starting at around 2:00 both nights) and drive around the vineyard with his thermos of coffee checking temperatures and deciding if/when they should turn on the wind machine(s) to protect the new growth from frost damage. 

Here, in a valley situation, the frost settles down into the low spots. Damage begins when it drops below 32F. The wind machine has powerful propellers that mix the warm air, above, with the cold air that’s settling on the vineyard. If the frost is severe, this won’t be enough and those who have them will light their smudge pots (little heaters that burn oil or diesel). Those with enough water available turn on overhead sprinklers to keep the new growth insulated by the ice.

So, when temperatures dip into the 30s, the vineyard manager’s got to get up, whether he likes it or not. Some years it’s a big issue (2008 was the worst year for frost since the early 70s – seems like I heard wind machines every night, just about, from mid-March to late April). If we get away with just two frost nights this year, that will be considered quite a good piece of luck! we figure we’re out of danger by mid-May. We’ll see…

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