Frost Protection In The Vineyards
One of the greatest risks to the health and success of the wine grape crop is
frost. Now that budbreak is here, we have to cross our fingers and be very
vigilant to protect the newly emerging shoots from a devastating frost.
It seems that such a frost has manifested itself this year already in a
couple of areas south of Sonoma County. So what is it that makes frost such a
problem, and how do we protect against these cold temperatures? Frost events can
damage the new shoots and possibly destroy the entire crop. As I explained last
week, when water freezes it expands. This ruptures cell walls in the green
tissue of the plant and the damage is irreparable.
Most of the frost we see locally happens on clear, starry nights with very
little breeze. Under these conditions, a strong inversion layer can occur where
the cold air settles down to the ground and causes frost.
There are several means by which we protect a vineyard. Site selection is one
first concern. We don’t always have a choice in planting areas, but as the
coldest air settles to the lowest spots, these are typically poor sites for
vineyard success and will always be susceptible.
Beyond this, the choice of vine establishment is important. The lower the
vine’s buds and shoots are to the ground the more they are susceptible to frost.
Timing of pruning is also a factor. Delayed pruning will discourage the vine
from budbreak by a couple of weeks. This delay may be enough to move beyond the
most dangerous time for frosts.
Also, once budbreak occurs, you might find vineyard managers out mowing their
vine rows. This effectively lowers the ground height several inches below the
emerging shoots and can help protect them from the coldest air.
Finally there are active methods of frost protection. The anti freeze candles are widely used in the vineyard and orchard. Most winemakers think the
antifreeze candles can against spring frost effectively.