Disclaimer: This post is a very basic explanation of cold hardy grapes. When I read and research about grape growing, I tend to skim over phrases such as "carbohydrate storage", "flow of photosynthates" and "phenological observations." Thus, I am not going to get too in depth on the scientific reasons for why the grapes we are growing can sustain cold temperatures because there are many other resources out there that can address this topic much better than me. My husband who's been studying this for over 12 years, can talk your ear off about it. But he's not the writer. I am just the vineyard wife with a journalism degree who is learning all she can about viticulture and winemaking from reading, listening, and doing.
Chardonnay, Zinfandel, and Cabernet Sauvignon are all household grape names. In fact, if you are reading this post, my guess is you've had a glass or two, or a hundred of these wines. These are some of your traditional grapes that have been growing in Europe for centuries. They are a species of plant referred to as vinifera. [Va-nif-er-a.] We don't grow vinifera grapes on our vineyard in Minnesota because these types of grapes could not withstand the cold temperatures. We grow french hybrids. I mentioned in an earlier post the grapevines we have planted and you can review that here. Some better known examples of french hybrids are Baco Noir and Seyval Blanc. Some better known northern climate french hybrids are Marquette, Frontenac, Frontenac Gris and LaCrescent, which are grapes we grow. Hybrids are crossbred from two different species of plants. So a vinifera plant could be crossbred with a different species of plant to make a hybrid. And they tend to be heartier plants and produce more fruit than traditional ones.
Fortunately for us, one of the best wine grape programs in the United States and is just down the street from us. The University of Minnesota Horticulture Research Center has a developed program and facility for grape growing and winemaking and over the years they have released hybrid grapes from their breeding program that they have found to be of the highest quality, cold hardy, disease resistant, and most importantly, have the ability to make great tasting wine! We buy our grapevines from local commercial nurseries and a portion of the sale from each vine goes to this program at the University.
The cold hardy grapes we planted are able to withstand temperatures of up to -31 F. Unbelievable, right? That is without windchill. And it is not unusual for Minnesota to experience absolute temperatures this harsh every few years. I wish I were that cold hardy! We picked our vineyard site for many reasons, but one that made it ideal is that the land has a southern facing slope, thus being able to maximize sunlight exposure and heat for the grapevines.
These are the pictures I took yesterday and just about froze my....hands off.
Note: Taking pictures in 7 degree temperatures (-12 with windchill) and gusting 20 mph winds without gloves on is not advised. See the sacrifices I make for this blog?
Grapevines are very smart. As early as the end of August, even before harvest, they prepare for the colder weather and begin what is known as "cold acclimation." They sense the days getting getting shorter and temperatures getting cooler and the vines start to harden off. This is where things like "carbohdrate storage" and "flow of photosnthates" come into play, but if you want more details on that, I would suggest heading over to Google and doing a little search. Or, if you are really curious to know, you can pick up the book, Northern Winework: Growing Grapes and Making Wine in Cold Climates.
Can you see all the posts in the distance? We (okay, mostly Aaron) planted 400 of them this fall.
As you can see, the vines have hardened off and are now in a dormant stage. There are definitely things we have be to watchful for over the winter, such as fluctuating temperatures, abnormally early frost or early thaw, the amount of snow coverage, which can be good to help protect the roots of the plant. These variables can all affect the cold acclimation process. However, as we all know, weather is one thing we can't control, so we have to roll with punches and do the best we can to work with whatever conditions come our way.
See our vineyard doggies playing?