For the most part, this past winter was not one of discontent. Unless, perhaps if you’re a winemaker. It’s a balancing act when it comes to managing freeze-thaw cycles in a vineyard. Most vines are resilient enough to withstand the below freezing temperatures for a time only to rise and bloom when it’s safe to wake up. This winter and spring were a little different, though.
While bud break in March is not unheard of, it usually it begins when the danger of frost has safely passed. Winter bud damage can occur at temperatures below -25 C; vine damage can occur between -28 and -30C. The level of damage also depends on the grape: Vidal and Cab Franc being heartier varietals can withstand extremes, but the more delicate Pinot Noir, and Gerwurtztraminer suffer the most when they are exposed to temps of below -10C.
But like anything in nature, adaptability is everything. According to an article in the University of Maryland Extension, buds acclimate in two ways:
- Dehydration ~ where water contained inside the bud and vine move into intercellular spaces. Shrinkage, if you will.
- Cryoprotection ~ sugar and protein complexes that bind water work as cryoprotectants which lower the freezing point of water allowing contents of the cell to ‘supercool’ without the generation of dangerous ice crystals.
The difficulty facing winemakers here in the Ohio River Valley is that spring came on early and strong with record mild temps, potentially causing grape buds to emerge earlier than usual. Bud break occurs approximately around late April through mid May. While early bud break allows for the potential of a longer growing season and riper fruit, it also increases the vulnerability to a late spring frost. If shoots are lost, the crop size decreases, yet the quality of the resulting wine can increase.
Matt Meineke, owner and vineyard manager of M Cellars in Geneva, Ohio says [via e-mail] , “with the mild winter early bud break was a concern but we do feel things should be in the clear at this point. Many growers use fans and we actually use a potassium/ calcium spray, and a little luck, to get by on our estate vineyards. On the vineyards we manage we use fans and of course luck!”
Temperatures in North East Ohio for March ranged from 28F on March 2 to a crazy high of 75F on March 8, with variations on that theme throughout the month, ending with a high on the 31st of 70F. It’s no wonder the buds were confused — I was. As temperatures began to decrease again, the frost, snow and ice could likely encroach upon the tender new vines, and damage could then take hold. Just how much damage remains to be seen. As Meineke explains, “ any extreme temperature fluctuation will cause the plants to deactivate from winter hardiness which is always a concern regardless of the variety. Some varieties are more tender, especially the vinifera wine grapes we grow such as Pinot Noir, Chardonnay, Cabernet Sauvignon, Riesling, etc.”
So what happens if frost bites the young vines? Having a plan B is essential to a successful season. According to Meineke, “if we have an early frost that causes damage, we would be using our secondary buds for production. This would cause production to be down and typically ripening may be delayed as well. That said, we would probably not be in a good position to make premium red wines, we should be considering premium rose wines as that is what nature has told us to do.”
As for any changes the consumer might see in terms of pricing, Meineke explains, “as far as pricing goes I don’t think we have a lot of room for an increase to the end consumer. We find local wines hard enough to sell on the open market and this would simply be one more reason for the end user to look elsewhere for their wine purchase.”
Even with this season’s fluctuations in temperatures, by the looks of things, the vines are all right. And so will be this year’s vintages.