Wisconsin vineyards are getting an earlier start with an earlier spring – but the early bird is not likely to get the worm in this case. Ryan Prellwitz owns Vines & Rushes Winery in Ripon. They grow five acres of grapes on-site and work with about a dozen growers around Wisconsin for the rest of their inventory.
Vines & Rushes makes between 10,000 and 20,000 gallons of wine every year depending on the crop. Prellwitz says this year will likely be on the lower side if the vines start budding before Mother Nature is done with her cold spells.
Growing degree days are heat units. They’re used to estimate the growth and development of certain crops, such as wine grapes. Prellwitz says the 30-year average for growing degree day accumulation around the first day of spring is about 16 days. This year, he says southern Wisconsin was seeing around 85. And in his neck of the woods, it was around 60.
Growing degree days are one of the variables that lead to “bud break”. Bud break is when you see green or a new shoot coming from the bud. Other variables contributing to bud break are the variety of the grape and soil temperatures.
The mild winter meant damage was low in the vineyard, but the warmth can lead to different issues.
When green shoots come early, temps under 32 degrees will bring negative results, Prellwitz says. He is going into the season anticipating a diminished crop or no crop at all. He doesn’t trust Mother Nature to stay warm after the buds break.
There are three buds within each bud. The primary bud is going to be fully fruitful. If that dies, the secondary bud will come out and be 50 percent fruitful. If that dies, then the tertiary bud comes. That bud is not fruitful but it keeps the vine alive.
Prellwitz’s preferred forecast is that the spring is cool and the buds don’t break until around May. Or that the buds break now and the temperatures stay above freezing from here on out. He doesn’t think either scenario will play out. Time will tell.
