What Happens When Vines Meet 115 Degrees?

Posted by Tom Wark on Aug 2, 2006

The spectacular heat wave that smashed into Northern California about a week and a half ago is well over We are back to normal here. In fact, looking out my office window I see the tell tale signs of a normal summer weather pattern: the final wisps of fog are blowing off an we are heading toward an 85 degree day.

The affects of the heat wave, however, are likely to have an effect on the grapes.

Will Bucklin, of Bucklin Winery and Old Hill Ranch vineyard (a client of Wark Communications) is getting ready to send a communique out to his distributors and distributor sales people in which he gives a description of the upshot of the massive heat we had (it was upwards of 115-120 degrees in Sonoma Valley and elsewhere). He puts it like this:

The vines do not like it.  They shut down vascular activity, close their stoma and turn their leaves away from the sun.  In the best case they lose a couple of days of photosynthesis but nature is not that forgiving.  At Old Hill, much to my surprise, it what the ancient, unirrigated vines that got through the heat with out significant damage but it was the younger irrigated vines that did not fare as well, especially ones that were already stressed out from what ever else was going on. Some lost lots of leaves and their grape clusters dried up into sour raisin bunches. Petite Sirah, of which there is plenty in our field blend, appears to be the most sensitive to heat.  I am guessing we lost about 10% to heat shrivel. 

In terms of the long term impact, the scuttlebutt among vineyard managers is that the shock of the heat may slow the size development of the grapes in essence reducing berry size.  Not necessarily a bad thing as smaller berries lead to more intense color and flavor. But when coupled with extensive sun-burn we may be looking at an interesting harvest in terms of tannin management.   In other words, look for the possibility of big, blocky wines in 2006.

The harvest in this neck of the woods probably begins in about three weeks or so with sparkling wine grapes being brought in. We’ll start to really swing into things around six weeks from now. It has been a very strange growing season with excessive rain in the spring and the most unusual heat I’ve ever experienced in this part of California in my life.