What happens when grapes on the vine hit freezing?

[AncoraImparo]

Our Seyval Blanc crop was demolished by birds this year. We're new to all of this, and they caught us off guard. We were ready to write that block off for the year. However, there are a lot of secondary clusters that have been maturing over the last month or so. Most are up around 18 brix, because we've had a very mild fall in Iowa. Some are higher than that. We may get 1/2 ton or more out of them. So we've been waiting to see how far they ripen before the first freeze of the year, which is late this year. Wednesday morning is going to kiss 30 degrees, then start trending warmer again. But I assume that means the party is over, and they won't ripen any more. How does that affect the grapes, though, if it's not a hard freeze? Does it do any damage to them? I wouldn't think so, because you can freeze grapes to use for wine. If we harvest that day, we should be good to crush and press with them, I would think. But if we wait a couple days, would that make a difference, leaving them on the vines a few days after a freeze?

 

[Ohio Bob]

My guess is the sugar in the grapes will prevent them from freezing at 30F. Vineyards that make ice wine can’t control the weather so they probably experience cooling/warming for weeks before finally harvesting the grapes.

 

[Ohio Bob]

More info...

https://www.evineyardapp.com/blog/2021/12/01/winter-harvest-and-ice-wine-production/

https://spectrumnews1.com/oh/columbus/news/2024/03/18/kimberly-generic-scaffold

 

[VinesnBines]

We had a heavy frost last Friday and the vines are done with photosynthesis. I still have several hundred pounds to harvest. Everything was holding last night so I’m optimistic I can finish this week. The reds are getting soft but the ssugard are concentrating, so I’m happy.

 

[Rice_Guy]

What is the term “the party is over”. They will not get more ripe since the leaves are killed. The next step is moisture is lost and raisining happens. They can be fermented, it is harder to pull raisins off stems so a crusher can make “peanut butter “.

 

[VinesnBines]

I was hoping for a couple more weeks. Last year we had stunning fall vineyard foliage.

 

[countygrapeguy]

Some grapes freeze better than others. I know that Vidal holds up well, not sure about Seyval, is it thick skinned?

Here in Ontario ice wine is picked at -8c (17F), usually in January after a few milder freezes.