For many winegrowers the question of whether or not to install a frost protection system is an economic one. Here in Napa, spring frosts occur often enough and winegrapes are valuable enough (even despite depressed prices in 2009) that the need for frost protection is almost a must. Whilst certain cultural practices like cultivar choice, vineyard location, late pruning and vineyard floor management can lessen the likelihood of frost damage, more often than not winegrowers will rely upon mechanical means to avoid spring frost injury. An overhead sprinkler system in the vineyard is one mechanical option for winegrowers.
With budbreak truly underway in our neighbourhood vineyards, last night (it was actually around 3.30 am this morning) was the first time this season that the vineyard fans have been employed. One fan will circulate enough radiant heat, hanging about in an inversion layer 20 - 30 feet above the ground, for approximately 8 acres of vines. When the threat of a severe frost is coupled with the lack of an inversion layer some winegrowers will fire up vineyard heaters which, in conjunction with vineyard fans, are extremely effective in protecting the nascent grape crop. Setting ablaze diesel oil will do that.
Smudge pots, or vineyard heaters as they have been renamed lest one offend the PC crowd, will burn up to one gallon of diesel oil per hour, emitting a thick, warm, smoky smog that the vineyard fans will then circulate to prevent frost injury. Common practice calls for about 25 smudge pots per acre, usually dotted around the border of the vineyard.
The fact that some vineyards choose to use this particular method of frost protection doesn't bother me one iota, as it usually only happens a handful of times each spring, if at all. In fact, I must confess to rather enjoying the smell of burning diesel in the morning as it wafts towards Vinoland: It reminds me of dodging double-decker buses and hackney cabs in Liverpool city centre on a busy Saturday afternoon.