It’s been a cool spring up here on Old Mission Peninsula. We often get asked how that is affecting our vines. As you’ll soon come to learn about asking questions in the wine industry, a common answer is “It depends,” which holds true in this case. With so many different factors involved in making wine, there usually isn’t just one answer. In regard to this year, we are OK with the cool spring, mostly because there has still been a chance for frost. If the days are cool, you can expect that night temperatures will dip down toward frost in certain areas (especially low-lying spots). If we’d had just enough warmth this spring to get the vines growing, then fell back into this cooler weather, we’d risk losing the new growth to frost and then have to rely on secondary buds for our grapes, which isn’t ideal (they often aren’t as productive).
So how are the vines doing? I can answer that scientifically first (I promise not to get completely scientific!). We use a method in agriculture called Growing Degree Days (GDD). It’s a measure of heat accumulation that helps determine plant development. The number comes from adding the daytime high temperature to the daytime low, dividing by 2, then subtracting a base temperature (we use 50˚F). This method gets tweaked a little when the average temperature falls below the base temp.
GDD = ((Daytime High + Daytime Low)/2) - 50
That number gets added to all the days prior to that to create an accumulated GDD of the year so far. Here’s a cool Michigan State University driven website that tracks GDD on Old Mission Peninsula: Enviro-weather (MAWN)
I’ve also compiled a chart to show the GDD of the last few years:
|
Year
|
GDD 3/1-5/3
|
Total GDD
|
Comments
|
|
2005
|
108
|
2695.6
|
One of the “best” years on record in N. Michigan
|
|
2006
|
152.1
|
2368.2
|
|
|
2007
|
97.3
|
2687.7
|
Had been 2nd to 2005 for quality
|
|
2008
|
118.7
|
2257.8
|
A pretty average Northern Michigan growing season
|
|
2009
|
76.2
|
1889.5
|
One of the coldest years we’ve had
|
|
2010
|
208.3
|
2607
|
Some argue this year was better than 2005
|
|
2011
|
47.9
|
?
|
|
Looking at the numbers to date (GDD of March 1st through May 3rd), this year looks a little scary, but those numbers can be a bit misleading. One warm day can increase that number by 20 or 25, and if we have a really warm summer, we can still catch up to a typical or warm year despite the cool spring we’ve had.
So I’ve presented you with data as an answer to the question of how the vines are doing. I also posed that question to Cornel, the winemaker, vineyard manager and one of the Lads here. His answer: He’s happy! We haven’t been hit with any frost this spring. The soil is starting to warm up, and there is plenty of moisture in it. He thinks we’ll have bud break by the end of next week (which would be just in time for Blossom Days).
So who’s right? Well… it depends.