Jan 27, 2014 – Many will agree that the Finger Lakes have been blessed the last few winters with relatively mild winters. Clearly that has not been the case these last two months. The polar vortex has brought sub zero temperatures to Western New York for this first time in several years. Unlike for our vineyard crew where such temperatures are just uncomfortable (yes, they are out in the vineyard almost every day) for our grapevines this cold puts next year’s crop or worse the vine’s very survival at risk.
The Tougher “Native Varieties”
First a little genetics and a talk of selective pressure, grapevines such as Diamond and Isabella are indigenous to North America and varieties such as Riesling, Pinot Noir and Merlot are from Northern Europe. Where you are from and the winters your parent vines were exposed to are responsible for your ability to survive low winter temperatures. Since North America has historically been colder than Northern Europe, what we called “Native Varieties” such as Diamond and Isabella can generally survive the temperature we have had in January of -4F to -11F without any damage to either the buds responsible for next year’s crop or the structure of the vine (the trunk and arms). If you are not from these parts temperatures that low can cause some damage. The first concern is for the buds that will produce next year’s crop. Temperatures of -11F can kill some but usually not all of the buds on varieties like Pinot Noir or Merlot but a variety like Riesling from Germany will suffer much less damage.
Location, Location, Location
Second just like in retail if you’re a grapevine it’s all about location, low winter temperatures vary widely depending on the location of the vineyard. On the coldest night so far this winter (January 22nd) we recorded a temperature in one vineyard at Swedish Hill of -11F compared to -4F on the same night in a second vineyard at our sister winery, Goose Watch. The difference is due to the aspects of the sites such as elevation, slope, proximity to Cayuga Lake, and how protected the vineyard is by woods. The difference can have a huge effect on the vines. The presence of cloud cover also helps hold heat so the temperatures are colder on a clear night. This effect can be very localized, as we’ve seen from tracking weather stations throughout the Finger Lakes.
We have six remote recording thermometers plus a weather station to monitor temperatures throughout the winter. Our vineyard manager then uses this information to make both long term and short term decisions. Knowing that some sites are colder than others the first decision is that we do not plant the more winter tender varieties on some of our colder sites although these sites are fine for “Native” varieties. Next, knowing that we may have suffered some damage on our European varieties, we will delay pruning these vines until after the potential for really cold temperature have passed. This is usually by the later part of February. Then our crew will gather buds from each of the vineyards and then use a simple technique to determine what percentage of the buds are alive (being farmers we are always optimistic and think about what’s alive instead of dead). Our pruning crew then adjusts the number of buds they retain on each vine depending on the level of damage. They follow this up once the vines are growing and will thin the number of shoots to further refine the crop the vines will carry in 2014.
Things could change if we see even colder temperatures over the next month but right now we still see the potential for a nice crop in 2014. But it’s still farming and in the mean time not being out in vineyard and getting the second cup of coffee is good for both the crew and the grapevines.
-Derek Wilber, Winemaker at Swedish Hill Winery