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What’s Happening in the Vineyard – August

August 14, 2014

The hot topic right now is the drought, and to put it plainly, it sucks! However, we actually had a good Spring and Summer:


  • No frost early in the season, and it stayed warm through June, leading to fairly low mildew pressure.
  • Sets are nice, meaning that the amount of successfully fertilized flowers is high. Each flower is a grape, the cluster of flowers before they fertilize (set) is called an inflorescence.


  • Overall, cool and temperate.
  • Cluster sizes are good. The rachis is the stem that holds all the flowers or berries together and rachis sizes are pretty good.
  • Berry enlargement, for the most part, seems to be a bit stunted. This leads to smaller berries which usually indicate some great flavor and color concentrations.

Monsoon Season
Monsoon season, which began in Paso Robles on July 14, brings with it increased levels of atmospheric moisture also known as humidity. Its arrival coincided with the beginning of veraison in Paso Robles Vineyards. Until veraison begins, mildew (a type of mold) is a persistent problem for grape growers worldwide. Paso Robles is blessed with some of the lowest mildew pressures (dry weather) of any quality wine region in the world. These low average humidities contribute to our daily large diurnal temperature change, which spurs ripening with acidity and intensifies the color in red varietals.

The product of a subtropical low-pressure ridge that rises out of Mexico and settles over Four Corners (AZ, NM, CO, UT), Monsoon season creates a prevailing wind that spirals clockwise bringing northern Mexico moisture into California. It is also responsible for the two hurricanes that recently hit Hawaii. To learn more about the Monsoon season see: http://en.wikipedia.org/wiki/North_American_Monsoon

The onset of ripening and the berries beginning to turn color is called veraison. As Paso Robles grape growers, we pay close attention to when it starts because the Monsoon season usually presents the highest daily humidity of the entire growing season. Version starts earlier on the east side than on the west, making these vineyards somewhat less susceptible to mildew problems associated with the Monsoon season. It’s quite fortunate that the timing of veraison, which ends the season where grapes are susceptible to mildew, coincides with the traditional starting of Monsoon season. After veraison, however, bunch rot can take advantage of the softening skin within the tight clusters of the maturing grapes. The increased humidity can create devastatingly huge problems during harvest if it goes unmanaged by a viticulturist. Careful management and tending to these vines is of the utmost importance as these vineyards approach harvest.

On the west side, growers stay on top of their mildew management during the Monsoon season as the increased humidity can make for an ideal mildew growth environment. This includes managing the canopy specifically affecting the amount of shading on the fruit. If mildew starts, the resulting scarring on the maturing berries can lead to increased instances of bunch rots in the Fall.

All in all, a grape grower’s job is never done, and an entire investment can be lost at any time during the growing season! So we all stay vigilant and look forward to the oncoming harvest.


Kevin Riley