With vines healthy and green and still in the rapid shoot growth phase, development of Tablas Creek Vineyard’s 2015 wine grape crop is exceeding Levi Glenn’s expectations. He’s the viticulturist for the 110-acre vineyard of mostly Rhône variety grapes in the Paso Robles appellation of California’s Central Coast region.
“The vines have jumped out of the gate and seem to have more vigor than in 2013 and 2014,” he says. “This should translate into producing a good amount of carbohydrate storage for next season. Both this year and last have been early. I think that benefits us the following season by giving the vines time after harvest to recuperate and continue to put stored energy away.
“Grenache seems particularly happy this year. “It pushes early, so I think it really benefited from the warm weather early this season.”
By the beginning of June shoot growth of most of his early-season varieties, like Grenache, Syrah and Vermentino was nearing the top wire. That compares to just 6- to 18-inches of shoot growth of such later-pushing varieties as Mourvedre and Counoise.
The tops of blocks have been growing at a faster pace than lower-lying areas. That probably reflects the differences in overnight minimum temperatures of as much as 10 degrees between the high spots and the cooler low areas. From the last week of April to the first of June overall growth, for the most part, has been slow and steady, Glenn notes. He expects that to accelerate with the recent return of warmer weather.
This year’s bloom has been more sporadic than usual. With some varieties it started in late April.
“That’s the earliest I’ve ever seen in coastal growing regions,” he says. “It was even ahead of last year, which was the earliest we had seen up to that point. Some blocks have taken more than three weeks to complete. I don’t expect bloom to be completed until the second week of June.”
Usually, the weather in this area is very favorable during bloom time, resulting in quick, even flowering. Given the unusually warm weather from January through April, May was surprisingly and unseasonably cool.
The bloom has been accompanied by a few light rain events and a fair amount of wind. In the last two weeks of May, every morning was overcast, a fairly rare occurrence in his vineyards, especially this time of year.
“The cooler weather has definitely drawn out the bloom-time period and really slowed growth on the later-pushing varieties,” Glenn says. “This may cause some uniformity issues down the line.”
For example, on one single vine he saw a cluster that was completely set, another that was in full flower, and one that hadn’t even started to bloom.
He doubts the small amount of shatter on Grenache and Syrah will harm yields this season.
“Crop size is looking to be average to slightly above average,” Glenn says. “We’ll assess crop-load before veraison and adjust accordingly. We’ve been real conservative with our crop levels during these drought years. The last thing we want to do is hang too much crop and put any undue stress on the vines.”
Water holding capacity of his soils, a mixture of limestone and clay, is quite high, he notes. Currently, soil moisture levels in the top to intermediate levels are good. He’ll continue monitoring them throughout the season.
Anticipating a warm summer, Glenn plans to keep most of the exterior canopy leaves to protect the fruit and thin the clusters to about 2 to 3 tons per acre to reduce overall stress on the vines.
Meanwhile, he’s minimized irrigation this season to discourage development of a large canopy that would need more water later in the growing season.
“Similar to the past two years, we’ll try to limit crop levels so the vines don’t go into a tailspin during the late summer when we get those extended heat spells,” Glenn says. “And we’ll continue our limited irrigation to encourage our vines to be more self-reliant.”
Although the Powdery Mildew Index was fairly high in late April, with few days over 70 degrees in May, the number has since fallen to around zero.
By the end of May he had sprayed the whole vineyard once and several early-pushing and mildew-susceptible blocks twice with a mix of sulfur and copper to control powdery mildew as well as phomopsis and stem botrytis. With warmer weather, he’ll switch to using mostly horticultural oils.
In the past, his vineyard has usually required treatment for leafhoppers in late summer. However, for the second straight year, this pest was quite active at budbreak, Glenn notes.
“We’ll wait until we get some high leaf counts of multiple stages of instars, probably around mid-June, and hit them with a combination of pyrethrin and insecticidal soap,” he says. “This has been our most effective organic treatment for leafhoppers. The horticultural oils have also shown some limited control.”
During the next weeks, his crews will be transitioning from shoot thinning to canopy management. Laterals and interior leaves will be removed from more vigorous blocks, while the exterior leaves will be left in place in the fruit zone. Based on fruit set, Glenn will start to do some preliminary cluster thinning on weaker vine and shoots.
This year, he’s planting another 10 acres of dry-farmed vines.
“About 25 percent of our vineyard is dry-farmed and during these drought years they’ve been quite successful, both in terms of quality and yield,” Glenn says.
He reports the wine grape market in his area seems to be quite strong across most varieties. However, the high number of non-bearing acres within the Paso Robles appellation could dramatically change supply and demand in the near future, he adds
Still, the big concern for him and other growers here is the availability and quality of water for their vines.
“In these dry years, the tendency is to irrigate more, even though there is less water available,” he says. “At some point if the drought continues this equation becomes unsustainable. With the lack of rainfall, salt accumulation and boron toxicity are becoming more widespread. For some farmers it becomes a real difficult decision. You need to get a decent crop to stay afloat. But, the more bad water you irrigate with, the more damage you are doing to your soil.”