Why we're celebrating our frosty mornings
December 09, 2013
This morning I arrived at the vineyard to find a landscape encased in frost:
This was the fourth time in five nights we've gotten down into the teens. The one night we didn't freeze we received about six-tenths of an inch of rain. Between the cold and the rainfall, the vineyard has been transformed in a week from fall to winter. Vines are bare or mostly so, the fall colors are gone, and we're starting to see the first little sprouts of green winter growth.
It should be obvious why we're thrilled about the water (though we're still far behind a normal winter, let alone the wet one we need to help ameliorate the two dry winters we've seen recently) but it may be less obvious why we're happy to see the cold snap. I'll explain, but first want to share some more photos to give our many fans who've only seen the vineyard in spring, summer or fall how different it looks. First, a view through our Grenache block, with the vine leaves on the ground outlined by frost:
Next, a second-crop Grenache cluster still clinging to the vines, covered with ice crystals:
And a close-up of the base of one of these Grenache vines, dead leaves and dry grasses outlined by the frost:
Finally, one more shot, of the many oak leaves newly on the ground in the last week. We do have evergreen oaks (our live oaks) but there are plenty of deciduous oaks as well like black oaks and California valley oaks:
It may not be intuitive why frosty winters are a good thing for vineyards, particularly given our agonizing battle with frosts in the spring. But grapevines are deciduous plants, and benefit from being forced into full dormancy. In a non-frosty environment (or a mild winter) a vine may continue to expend energy growing new canopy or at least sustaining the canopy it grew during the summer, gradually sapping the vine's available resources for the next spring. A hard freeze kills off any leaves and stops this gradual leakage of sap, giving the vine more reserves for the growth in the spring.
Typically, we see our first hard freeze here sometime in November, with December and January our two coldest months. By February and March the longer days and higher sun angle start to warm things up again, and we typically see bud break (the point at which the vines start sprouting new growth) in late March or early April. Before bud break, we're happy to have as many frosty nights as we can get, and it's particularly beneficial to have cold nights in March, to delay the bud break that then makes us vulnerable to a frost. We're generally out of the danger zone by mid-May.
So, for the next four months or so, we'll be celebrating our cold nights. If you've got an in with the weather gods, please keep it up. Just ask them to throw in a little more rain while they're at it.