This winter has very much been one of phases. November was chilly but almost entirely dry, which got us into dormancy early but put us a bit behind in cover crop growth. December was very wet, with 6.66 inches of rain and 13 days with measurable precipitation. January and February stayed chilly (18 below-freezing nights) but saw very little precipitation. The sun and the saturated soil from our wet December produced a vineyard that grew greener by the day, but since wet soils hold temperature better than dry ones, raised the specter of very early bud break if we didn't get more rain soon. But then March turned wet and remained cold, dropping soil temperatures and keeping the vineyard in stasis for longer than I thought possible. The rainfall-by-month graph for the winter so far shows the whipsaw nature of what we've seen:
The vineyard's long period of dormancy is ending. The proliferation of California poppies are an indicator that the lengthening days and the warm sun will begin to wake up the vines:
Budbreak, as you probably guessed from the name, is the period when the grapevine buds swell and burst into leaf. It is the first marker in the growing cycle, a point when we can compare the current season to past years. Upcoming markers will include flowering, veraison, first harvest, and last harvest. And like harvest, budbreak doesn't happen for every grape simultaneously. Early grapes like Viognier, Grenache Blanc, Grenache, and Vermentino tend to go first, followed by Syrah, Marsanne, Tannat, and Picpoul, and finally, often three weeks or more after the earliest grapes sprouted, Roussanne, Counoise, and Mourvedre. And it really is just starting. We only have budbreak in Viognier, the two Grenaches, and (bizarrely) the very top of one Mourvedre block. The below photo is Grenache:
This year is later than many years last decade, and a month later than our record-early 2016, but it's only about average for what we'd have expected historically. When we saw first budbreak the last dozen years gives a good overview:
2019: Late March
2018: Late March
2016: Very end of February
2015: Second week of March
2013: First week of April
2011: First week of April
2010: Last week of March
2009: Second week of April
2008: Last week of March
It's important to note that the vast majority of the vineyard is still dormant. I was only able to find leaves in our earliest-sprouting grapes and only at the tops of the hills, which are warmer than the valleys, where cold air settles. And even where it's begun, with the exception of the earliest Grenache blocks, all there is to see is swollen buds like the one below, from the Haas Vineyard Pinot Noir:
It will be at least another few weeks before we see sprouting in late-emerging grapes like Counoise or Roussanne, or in low-lying areas. This Mourvedre block is one of many that show no signs of sprouting yet:
Why does budbreak happen when it does? It's mostly a question of soil temperatures. Grapevines (and all deciduous plants) are spurred by rising soil temperatures to come out of dormancy and begin their growing season. Evolutionarily, plants are trying to balance competing goals: to sprout early enough to achieve maximum carbohydrate generation from photosynthesis (i.e. ripen their fruit so animals eat it and distribute the seeds) while staying dormant long enough to avoid suffering damage to their reproductive prospects through frost.
Frost is on our minds. Before budbreak, the vines are safely dormant, and a freeze doesn't harm them. But once they sprout, the new growth is susceptible to frost damage. April frosts cost us roughly 40% of our production in both 2009 and 2011, and we don't feel truly safe until mid-May. So, we've still got more than a month to go before we can relax, and I'm thankful that it will be a few weeks before our later-sprouting varieties and our lower-lying (read: more frost-prone) areas are out enough to be at risk.
You might think that earlier budbreaks increase your risks of frost. And yes, all other things being equal, having fewer nights where you have to worry about temperatures dropping below freezing is better than having more. But if you look at the two most recent frost years (2009 and 2011) both of those saw budbreak in April. Is it possible that the same conditions that keep a vineyard dormant longer in the spring raise the risks of frost damage once they finally do sprout? I think so. California weather patterns tend to be long-wave patterns, where conditions are more likely to be similar to what they are now in two weeks than to have changed entirely. That's unlike, say, Vermont, where I grew up, where it always seemed to me that each week's weather could just as easily have been generated by a random weather generator.
That said, looking at the long-term forecast offers some hope. We're supposed to get one more chilly late-winter storm next weekend, but it doesn't seem likely to be cold enough to damage the tops of our hills, and it doesn't seem like we will have progressed far enough for anything else to have sprouted. After that, we're expecting drier weather as the storm track shifts north. But there's a long way to go.
Meanwhile, we'll enjoy the rapid changes in the vineyard, and the hope that always comes with the emergence of new buds. Please join me in welcoming the 2020 vintage.