Basic Winegrape Viticulture

Last Monday was our first session of this class (because the 17th was a holiday) and it was a good review of some of the concepts I learned last semester. I was supposed to have taken this class in the Fall, but postponed until this semester because of scheduling issues.....I think this class will bring more clarity to a lot of what I was introduced to last semester. Last week we covered historical and climatological perspectives of the grapevine - where Vitis vinifera (genus and species of the most popular wine grapes) originated - the trans-Caucasus mountains, between the Caspian and Black Seas - and how it ended up all over the world. The most significant fact about V. vinifera is that it is very susceptible to phylloxera, an aphid-like insect that loves and lives on grapevine roots and which has no natural enemies. It is called the world's worst grapevine pest. In the late 19th Century, a phylloxera epidemic wiped out 9/10 of Europe's vineyards when cuttings from American vines were planted. Because phylloxera are native to N. America, the roots of American grape species were largely resistant, but those in Europe were not. Fortunately for the Europeans, researchers discovered that their vines could be grafted onto disease-resistant American rootstocks. The discovery saved their grape industry, and this method of grafting onto pest-resistant or cold-hardy rootstocks is still used today.

We discussed the concept of terroir - a French term meaning "taste of place" - which is the idea that the environment (soil, climate, and viticultural practices) in which vine and fruit develop determines how fruit (and ultimately wine) will taste. Climate includes "macroclimate" - that of a region (California); "mesoclimate" - that of a particular site (Russian River Valley); and "microclimate" - that within the canopy (leaves) and fruit zone of the vine. The system of Degree Days is an important system that is used to determine a region's climate in order to select the most appropriate cultivar (i.e. Chardonnay, or Pinot noir) to plant in a particular place. Because different cultivars have different heat requirements to optimally ripen their fruit, it is essential to be able to quantify and calculate a region's heat units during the growing season (April 1 - Oct 31). For all days, the average of the daily maximum temperature and the daily minimum temperature is reduced by 50 (50 degrees F is the Degree Day threshold for grapevines). All numbers (days) are added together and fall into one of five regions (Region 1 being the coolest and Region 5 being the warmest).