We have a forecast of 28 Monday morning. As I write, it is about 11 PM, and the temperature is already in the 30s. We expect a frost Tuesday morning. There is a chance of frost next we, April 2. That is still a bit far away.
Before I started breeding grapes, these late frosts bothered me a great deal. I would worry about how to protect the grapes. As a breeder, a different problem presents itself. How to use the response to these frosts to improve my breeds?
For example, I could simply remove every vine that suffers from the freeze. At this point, about 15% of the vineyard has sprouted leaves. Five or six have quite a few. All these leaves will be turned into what reminds me of toast. The leaf will crumble up into dust if you rub them between your fingers. All the leafy xylem vessels pop due to the expansion of freezing water and the leaf dries out within a day or two.
It isn't clear what will happen to the vines in their various states of spring growth. With the leafy vines, the canes may die, forcing the roots to put up new shoots from the ground. Generally, the fuzzy buds (no growth, just a little fuzz) can handle the freeze without any trouble. The swollen buds are probably toast, but the canes may get through the night without to much damage.
We will see.
The general idea will be to select for late bud break, and cane survival. That isn't hard to do if there are 4 vines from a single cross, and one of the four dies back to the ground. It is harder if there are 4 vines and only one still have a viable cane. Do I remove the other 3?
I went through the vineyard marking all the vines that had leaves. These are the most at risk. I was struck by the dormancy of local vines. They were the smart ones, still fast asleep. The mustang, generally early to leaf was still dormant, only a little fuzz. The local cinera was still dormant, but that wasn't a surprise. I think all the local cinerea crosses were still dormant. A couple of the Virginia cinerea crosses had put out leaves, though. The champini and doaniana open-pollination (OP) crosses were largely leafed out. The few vinifera seedlings I've got were generally leafed out, too.
Deciding what to study as these vines develop this year will be an interesting challenge. A number of these vines are going to have to go.
According to a weather site a couple of miles up the river, the low was 19 this morning. Monday, the low was 22. The forecast for tonight is 28.
ReplyDeleteI checked the frost damage tonight, by flashlight. All the leaves on the west side of the vineyard were lost, but about half the leaves on the east side survived. the west side is in the open, but the east side is half under live oaks, so the shelter provided by the oaks must have protected them. I have not figured out a pattern. In one case, two vines were less than a foot apart and had equal numbers of leaves. One was wiped clean of leaves, the other had half looking fine. Maybe some vines were better at surviving frost.
I did a careful review of the frost damage this morning, 3 days after the Tuesday freeze. The damage was less than I expected. Several vines, especially those with cinerea in them, went through the freeze without losing leaves. Swollen buds seemed to survive without much difficulty. I removed two vines that were members of crosses that needed to be thinned, and both had lost every leaf while siblings had leaves without any sign of damage. One was an 'L50s x Trebbiano'. The other was a champini x op cross. There are probably a number of vines that have dead canes at this point due to very early budding during early March when frosts took place every week. We won't know which these are until they start budding from the roots while the cane fails to bud.
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