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September 2017

Harvest at the Three-Quarter Pole: A Return to a More Normal Time Frame, with Solid Yields

Late last week, we welcomed our first major picks of Roussanne and Mourvedre into the cellar.

Roussanne in tank

Mourvedre in tankAnd with that, the home stretch of harvest officially began. There will be a lot of harvest chalkboards that look essentially like this one over the next couple of weeks:

Harvest chalkboard Roussanne and Mourvedre

Where we are, one week into October, is remarkably similar to where we'd expect to be, if we were predicting at the beginning of the year.  We're done with early grapes like Viognier, Vermentino, Syrah, Marsanne, and Grenache Blanc.  We're mostly done with what we consider mid-harvest grapes like Grenache and Tannat.  And we're just getting into our late grapes, Mourvedre, Roussanne, and Counoise.  Given that we're comparatively heavily planted in these late grapes, we still have more fruit out than many of our neighbors.  Still, we expect to be harvesting pretty steadily for the next two weeks, and to be done before the end of the month.  If this seems late, it's likely a matter of perspective, because most of our recent years have been early.  While 2013, 2014, and 2016 were all done by mid-October, our average finish date of harvest this millennium has been October 29th.

With the first complete blocks harvested, we've been able to get the animals back into the vineyard.  Right now, they're in the head-trained vines on our Scruffy Hill block, visible from Vineyard Drive if you're coming in from the south:

Animals back on Scruffy

Although we're where we'd expect to be in the harvest sequence, it hasn't always been smooth getting here.  Harvest began with a significant heat wave that sent temperatures soaring over 102°F nine days in a row.  We then got nearly three weeks of temperatures more than 5°F cooler than normal. In the last two weeks, temperatures have been more or less normal for the season, without any noteworthy heat waves, and with only one day significantly cooler than normal, a bizarrely chilly October 3rd where the sun didn't break through the fog until noon and the day topped out at 64°F:

Avg Temps 2017 vs Normal Sept Oct

For the month of September, we had 11 days warmer than seasonal averages, and 19 days cooler than average.  Even with the heat wave that began the month, our average high was 86.3°F, two degrees cooler than average. These cooler days allowed the vines to recover from the stress of their early-season heat wave, and allowed the cellar to free up tanks and get ready for the next push.  A graph of the harvest by week shows the ebb and flow. Normally, you'd expect a sort of bell curve, with thin tails at the beginning and end and the busiest weeks in the middle.  Not this year:

Harvest by Week

In terms of yields, with a significant number of grapes done, things are coming into focus.  It looks like yields are up from 2016, and a bit above average for the first time since 2012.  The varieties we've finished harvesting are up an average of 32.9%, with the most noteworthy recovery from Marsanne, whose yields had been so depressed by the five years of drought that we were getting less than one ton per acre last year:

Grape 2017 Yields (tons) 2016 Yields (tons) % Change vs. 2016
Viognier 18.9 14.2 +33.1%
Marsanne 13.8 4.5  +206.7%
Grenache Blanc 46.4 30.6 +51.6%
Picpoul Blanc ? 7.7 ?
Vermentino 22.2 19.0  +16.8%
Roussanne ? 47.0  ?
Grenache 73.1 58.8  +24.3%
Syrah 41.5 36.8  +12.8%
Mourvedre ? 62.7  ?
Tannat 18.3 12.3  +48.8%
Counoise ? 18.0 ?
Total so Far 234.2 176.2 +32.9%

Even with the higher yields, sugars are up a bit this year, which is a sign of the health of the vines.  Thank you, rainy winter!  The growing season, the yields, and the character and numbers of the grapes at harvest remind us most, so far at least, of 2005: also the first wet year after a string of dry years, with a long growing season and a relatively cool harvest period.  We aren't likely to go as late as we did that year -- November 7th -- but if we get a similarly robust vintage, we'll be happy. 

Meanwhile, we'll enjoy the last couple of weeks of grapes on the vines. By the end of the month, we'll have to wait another year for views like this:

Counoise on the vine early October


Why Paso Robles is So Well Suited to Late-Ripening Grapes

This morning, when I got back to the winery after a week on the road, my first order of business was to check in on how harvest was going. I was happy to learn that things picked up a bit last week. After more than two weeks of chilly fall weather, it had warmed back up, with eight days of perfect ripening weather: daytime highs between 83°F and 93°F, and lows between 41°F and 51°F.

And still, when I asked Chelsea how she was feeling, she responded, "this is definitely the first October 1st I can remember where we haven't been stressing about tank space."  Although harvest picked up from the glacial pace it was in mid-September, we are still waiting on most of our Marsanne, Roussanne, Mourvedre and Counoise.  Why? Blame the cold nights. Here's Neil, this morning, next to our first pick of Mourvedre. It was 52°F at 8:30am:

Neil looking chilly

We're used to this here, but most of the Mediterranean world is finishing up harvest about now. Beaucastel's Facebook page (for example) shows that they brought in their last fruit on September 29th:

It's not like this year is an outlier for us, either.  Over the last 15 years, we've averaged a last pick off the estate on October 29th, and our earliest-ever finish was October 7th in 2013.  Six times in those 15 years we were still picking in November. 

To explain why grapes take so long to ripen in Paso Robles, I'll have to detour briefly into some basic plant physiology. Bear with me here, or just skip to the end of the bullet points if you'd like the conclusions without the chemistry. There are a number of different processes which limit a grapevine's ability to photosynthesize at low temperatures. These include:

  • The tendency of plants to close their stomata (pores in the leaves) in response to cold, limiting respiration and the uptake of CO2
  • Carboxylation (sorry for the long, technical term) is the first stage of photosynthesis, whereby CO2 molecules are turned into an acid known as 3-PGA. Carboxylation efficiency declines as temperature declines
  • The electron transport capacity of plants is reduced at low temperatures
  • An enzyme known as Rubisco, essential to the first step of carbon fixation in photosynthesis, is inefficient at low temperatures

So, in essence, at cold temperatures, plants take in less CO2 and are less efficient in turning the CO2 that they do take in into the starches that fuel both plant growth and fruit ripening.  Grapevine ripening proceeds most efficiently between 30°C and 35°C (86°F and 95°F).  It drops dramatically below 25°C (77°F), and reaches zero at 10°C (50°F).  A summary graph from a technical paper published in Plant, Cell, and the Environment shows the combined effects pretty clearly:

Figure-7-CO2-saturated-maximum-rates-of-photosynthesis-meanSE-of-Semillon-leaves-as

For context, take a look at the temperature curve for the most recent 24 hour period:

Temperature C by Hour early October

You can see that while it did get warm, topping out around 30°C (86°F) yesterday afternoon, it only lasted until sunset just after 6pm.  By 8pm it was already down to 20°C (68°F). It bottomed out at 6.4°C (43.6°F) at 6am and wouldn't rise back up above 20°C until noon today.  So, over the last 24 hours, our vineyard spent 5 daylight hours over the 25°C temperature at which photosynthesis happens efficiently (2pm-6pm yesterday). Five other daylight hours (9am-1pm today) saw temperatures at levels where some photosynthesis can happen. Two daylight hours (7am-8am today) saw no photosynthesis at all because it was too cold.  And for 12 hours the sun was below the horizon. 

We are far from the only, or even the most extreme, location in Paso Robles.  The temperature grid from the Paso Robles Wine Country Alliance shows other areas that dropped near freezing last night.  Most show diurnal temperature swings of 40°-50°F. 

Temperature Grid October 2nd 2017

So, what does all this mean? That once you get into the end of the growing season here in Paso Robles, it's hard for grapevines to do too much photosynthesizing. That's a benefit, because you can get the last little bits of ripening on your late-ripening varieties slowly, so they continue to build complexity without accumulating too much sugar.  In general, the longer your grapes can stay on the vine before they get to the ripeness levels you want, the more complexity your wine has.  That's why a generally accepted bit of wine wisdom says that the best examples of different grape varieties can be found at the northern limit of their ripening range. So, the best Sauvignon Blancs tend to come from the Loire, and not Bordeaux. The best Pinot Noir tends to come from Burgundy, and not the Languedoc.  And the best California Chardonnay tends to come from cool coastal pockets where the fog slips in from the Pacific, not from the Central Valley.

Of course, at some point, you do need to get things ripe.  Grapes that don't make it to good ripeness produce wines that are green and bitter: no one's idea of a pleasurable drink. But here too Paso Robles has an advantage: that we don't tend to get our first serious rain until mid-November.  If we need to wait, we wait.

Hopefully, this particular waiting game is over for a while. But if it's not, I'm still confident we'll be OK. Thanks, Paso Robles.