The Beauty of Frost Protection

By Chelsea Franchi

The beginning of last week brought some low temperatures to the vineyard and Executive Winemaker/Vineyard Manager Neil Collins and Viticulturist Levi Glenn were forced to work through the night to ensure that the 2013 harvest didn't get fried by frost.  When freezing temperatures are forecast, that's a scary thing for everyone working at a winery, but especially those who man the frost protection devices.  On these nights, the person in charge of frost patrol (usually Neil, who lives on the property) calls our weather post every hour on the hour to track temperature patterns.  And if that temperature drops, it means suiting up in the middle of the night - when it is quite literally freezing outside - to fire up our frost fans, hang curtains (which help direct air flow from the fans) and turn on sprinklers.

By the time I get to work (at 7:00 am), the sun is coming up and the danger of frost damage is past.  However, frost protection is still in full force at that time.  Pulling into the winery, it sounds like we have helicopters trying to land in the vineyard (some of those frost fans are incredibly powerful and move a LOT of air) and the sprinklers are still on.

This is the view I am greeted with on those chilly mornings:

While this is far from a welcome sight from a vineyard or winemaking standpoint, it is truly breathtaking.  Those are low-flow overhead sprinklers at work, pulsing water onto the vines.  This process leaves icicles hanging from the trellis wires and encapsulates the freshly sprouted foliage in glassy sheaths of ice. 

While this may look like the opposite of frost protection, this is exactly what it should look like.  When water freezes, a chemical reaction occurs in which liquid water (which has a lower density) is changed to a phase with a higher density (ice).  As this happens, molecules slow and condense and in doing so, they release energy - and heat, called "latent heat".  While this process does not produce enough heat to warm the plant, it does provide enough heat to prevent the plant temperature from falling below the freezing point.  As long as water continues to be applied (this is imperative), the process of water changing to ice (and releasing latent heat) will continue to protect the plant until the outside temperature becomes warm enough to melt the ice.  Only then can the sprinklers be turned off.

We're going to keep our fingers crossed that our current (gorgeous) weather conditions are a trend, but if you cross your fingers, too, that probably wouldn't hurt.  We appreciate support in all forms.