Vineyards in Paso Robles worry about frost every year. Springtime frosts can be devastating, killing the new growth and forcing the vine to dip into its reserves to re-sprout from secondary buds. We've lost around 40% of our crop from April frosts in years like 2001, 2009, and 2011. I've written (more times than I care to remember) about the nightly worry we face between bud break (typically in late March) and mid-May, when our nights have warmed enough that we're out of the danger zone.
We're worrying about frost now. But not because we might lose production if it freezes. Instead, we're worried that it hasn't frozen yet.
Three weeks ago, most of the vineyard looked dormant. Leaves were off varieties like Roussanne, Counoise, Grenache and Mourvedre, all of which worked late into the season to finish ripening their grapes, exhausting themselves in the process. The earlier grapes that had to expend less energy were brilliantly colored in typical autumn splendor. All that's normal enough for late October. But with the nice rain we received in mid- and late-October, many of these blocks have sprouted new growth. A Mourvedre vine behind the winery is a good example:
Ironically, a lack of frost in the fall can have the same negative impact as a late frost in the spring, as a grapevine spends its stored energy on growth that won't be usable to ripen the fruit. It will freeze, sooner or later, and this growth will die. We'll come through and prune during dormancy, and when the vine sprouts for the 2017 season in April, it will do so with less vigor than it otherwise would have because of these depleted reserves.
Typically, this fall growth isn't a problem in Paso Robles, because we usually get our first frost more or less in conjunction with our first rain. But this year, the rain we've received so far has been tropical in origin, instead of moving south from Alaska with Arctic air behind it.
That's not to say the rain we've received has been unwelcome; getting rain this time of year has meant that the cover crop is already well established and we're unlikely to see much erosion should we really get dumped on. And drought, right now, is a bigger worry for us than a little pointless end-of-season growth. It's going to freeze sooner or later; in a typical winter, we see 30 or 40 nights drop below freezing, and in December and January frost is a sure thing.
But the scene below, as pretty as it is with bright green grass and autumn colors on the vines, isn't ideal. Each week we continue to see warm nights will sap a little of next year's vigor. Winter can come any time it likes, please.