Anticipating Winter's Dormancy

As the temperatures in Santa Barbara County get closer and closer to freezing, the vines prepare to go dormant
Nov 23, 2009

It's getting noticeably colder with each passing day. I am excited to hear reports from my friends that there is already snow in the Sierras and in the Rocky Mountains. Some have already been strapping on skis and snowboards. Winter and the anticipation of what goes with it are arriving, both the fun and the work.

Here, the vines, tired and spent, have begun shutting down but haven't gone fully dormant yet. Further inland it has been colder at night and vines are further into dormancy. Soon we will get much deeper and colder weather across all of Santa Barbara County and the vines will all go dormant. This is very important because a deep, uniform dormancy is necessary for the vines to emerge simultaneously into an even budbreak in the spring.

When we created the boundaries of the Sta. Rita Hills American Viticultural Area (AVA), the location of the western boundary (nearest the coast) was delineated based on the consideration of vine dormancy. It is well known that, in summer, the cold sea air from the Pacific keeps this AVA very cool. The chill of this maritime influence distinguishes our region and is why you will see people wearing sweaters here during the summer.

However it is less well known that, in winter, the ocean has the opposite effect—its proximity buffers the cold winter air, keeping the region warmer than further inland.

Westward from the Sta. Rita Hills, closer to the ocean, the roses and deciduous trees do not go dormant every winter. It is not uncommon during some years in the city of Lompoc to see roses in full bloom in February. Subsequently the western Sta. Rita Hills AVA boundary was drawn taking into account the proximity of the ocean and the effects of topography on air movement in order to only include those lands assured of sufficient winter chilling hours.

At this point in time, I have not yet seen frost in the vineyards I farm, but have noticed a few low-lying vineyards in the nearby area singed by frost where the cold air has pooled and left its mark.

The area where the cold air settled is dramatically visible because as the slope rises above a visible elevation contour there is no damage. But below that elevation, the vine leaves are scorched from air temperatures that have reached 32° F or below. It is surreal to look across these vineyards and see or imagine by way of the color of the vineyard's leaves where the cold, heavy air collected like a lake.

I wanted to share these observations after writing an earlier blog (of Halloween and Harvest) where I briefly discussed a few elements of terroir. Elevation is an important element of terroir because location on a slope can determine relative soil depth and what is available for the vine roots to explore and find nutrients and water. But elevation also is important because it influences air movement and rainfall patterns, temperature gradients and thermal effects, with resulting positive and negative influences on vine and fruit development throughout the year.

Harvest United States California Santa Barbara County 2009

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