Incredibly difficult growing grapes on the very fringes of what is considered grape growing territory. And as far as the world goes, all of Canada is on that fringe. We have really cold winters and short summers. Reminds me of the Sass Jordan song "Going Back Again". She is singing about Montreal, but she also notes the cold, and embracing where your from, singing ...
Some of my favourite lines from one of my favorite Sass Jordan songs! But it captures a bit of the reality of Canadian winter. We are not glowing with heat or long seasons and for the most part from BC Okanagan to Ontario Niagara we are talking about a 6a/b plant hardiness zone. Exceptions are a very small area in the very south Okanagan as a zone 7 then warming as you head west towards Vancouver to a Zone 9, then near Windsor Ontario at Zone 7, and then the very south tip of Nova Scotia towards Yarmouth which may be a zone 7. Consider that California and the great grape regions in Europe are 2-3 zones warmer than these areas in Canada.
The vast majority of the wine growing area in BC and Ontario is Zone 6a/b. In a 6a hardiness zone you can expect average winter cold in the neighborhood of -20.6c to -23.3c. A 6b hardiness zone is a bit warmer with expected average winter cold in the area of -17.8c to -20.6c. What is important to recognize is that these are averages.
Given that most of the wine grape growing area in Canada is in a 6a or 6b climate one could then expect that every 5-10 years there will be a winter cold snap that will take the thermometer down to the -25c level or colder. This temperature level is really important to note, because most of the vinifera wine grape varieties grown in Canada (Merlot, Pinot Noir/Gris etc.) are not really cold hardy and are significantly damaged at temperatures below -23c and especially so beyond -25c.
As best we can tell given local historical records and our own climate records taken for nearly two decades, we have a plant hardiness zone of 6a at the vineyard. Over this period our winter lows have ranged between -16c and -27c (last winter) with an overall average in this period of -21.4c.
The average is important because we expect we are going to get highs and lows that are outside the range of a 6a plant hardiness zone. Our warmest winter puts us into a 7a zone and our coldest puts us into a 5a plant hardiness zone. So from our experience and evaluation of records, pretty much in any 10 year period you can expect 1 or 2 really warm winters (warmer than a 6a zone) and 1 or 2 really cold winters (colder than a 6a zone).
We planted vines in anticipations of those anomalous cold years and looking for those varieties that were at least 1 zone hardier than our location. Hence we grow hybrids such as Marechal Foch, Leon Millot, Marquette, Castel, L'Acadie Blanc, Evangeline and are adding Frontenac Blanc this year. The least hardy of these are Castel and Evangeline but they can still withstand cold to about -25c to -27c.
There are many more hybrid selections grown that can withstand these cold temperatures or colder, but overall they represent a tiny fraction of the wine grape crop grown across Canada.
Which takes me back again to Montreal - the eastern townships rural area south east of Montreal and a small grape growing area located there. Very cold winters, Zone 4b-5b, but they have thriving vineyards that I've toured there. They embrace their location and make spectacular wine with cold hardy grape varieties suited for those locations. Perhaps a little warmer there than the winter Sass Jordan suggests but nonetheless, extremely hard winters for grape growing but its done well with varieties suitable for those conditions.
