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Understanding “Degree Days”, White Film on Wine, and Glass vs. Wood

Q Is there any wine grape that can be successfully grown in an area with a heat summation of 1,200? I am near the Pacific Coast and summers are not very warm, typical 70s °F (low 20s °C), sometimes in the 80s °F (high 20s °C), but always cool at night. Some people say that Gewürztraminer or Pinot Noir may be able to grow here. Do you think they can grow under those conditions? Tim Doherty Blue Lake, California A Interestingly, even though your heat summation units are low, you are close to the Pacific Coast and so therefore I am guessing your winters are mild. Vitis vinifera grapevines grow at a minimum of 50 °F (10 °C) and winter kill at around 0 °F (-18 °C) so during the growing season, during the day, your 70s and 80s °F (20s °C) should do quite nicely. The “Winkler Scale” or “UC Davis Heat Summation Scale,” which measures what are dubbed “degree days,” is only a rough guide to which varietals will thrive in which areas and is solely based on