February is the new April

How time flies. It’s been nearly two years, almost to the day, since I last wrote on this blog. And in 2015, when I posted that story, February was a different kind of month; not just cold, not just bitterly cold, but so cold that we wondered if our vineyard would survive the night. The forecasts said temps could reach minus 13 degrees on the night of February 20, and that was scary.

If it’s February, then I guess it’s Spring.

Vines can survive freezing weather without a problem, especially if they’ve had time to harden off (which requires some cold weather) before the big chill. They can withstand temperatures down into the teens and even below zero. But negative 13 degrees, which is what was forecast two years ago? That’s a killing freeze.

So flash forward to this February. We had two kinds of flowers blooming on our property, and I saw cherry trees and forsythia in full bloom last week. We spent evenings on our deck, not just to enjoy the spectacular weather, but to avoid having to turn on the air conditioning.

And our vines? Well, let’s just say I’m praying for them.

We had some colder weather move in, and the overnight lows were close to freezing. But daytime temps were well above 50 degrees every day, and that’s when vines start coming out of their winter slumber. At some point, the buds swell, then break, and then start sending up shoots. That’s when they’re vulnerable. A late frost in April or, for that matter, a normal frost in March, could threaten much of this year’s crop.

That happened last year. Shortly after budbreak, about the time that the shoots were an inch or so in length, we had two days in which the temperature dropped below freezing in the very early morning, killing a significant share of the primary buds on all of our vines. The secondary buds seemed to survive, and they sent up shoots. But those buds aren’t even remotely as fruitful as the primary buds.

We lost most of our crop. We might have had 35 gallons of wine in 2015, and perhaps 20 percent of that in 2016. Other vineyard managers i spoke to around the state relayed similar experiences.

So, what to do? Well, there are lots of ways to protect vines from late frost events, most of them very expensive. Some vineyards light fires, others spray water over the vines. (When water freezes, it releases heat. The only problem is that you need to spray water for the duration of the frost event.) Other vineyards rent helicopters to fly over the vines, forcing warmer air down. Of course there are only so many helicopters available on any given night, and they aren’t cheap. Maybe for our small hobby vineyard we could buy a big drone to fly over the vines.

As it happens, the annual winter technical meeting of the Virginia Vineyards Association began last week, and the unseasonably warm weather was a definite topic of conversation. In fact, one of the sessions was all about using sprays to combat late frost.

Michela Centinari of Penn State University discussed two in particular: Amigo oil, which can be used to delay budbreak, and KDL, which may lower the freezing point of vine cells.  Both approaches seem promising, and I think we might lay in a stock of KDL for next year.

But for now we have one more trick up our sleeves that could work – late, or delayed pruning.

Each year, while the vines are still dormant, we prune to get them ready for the growing season. We mostly use a technique called cane pruning, which involves taking a shoot from the previous season and laying it down on the fruiting wire. That shoot, now a cane, will send up new shoots that will bear fruit.

The second, which we employ on some vines, is called spur pruning. Instead of laying down a new cane, we trim the shoots on the old cane to two or three buds, each of which will send up a new shoot that will bear fruit. Some will get pruned off during the growing season.

What’s important here is that the process of pruning stimulates growth. Many vineyards have begun employing a process known as double pruning, in which they trim away the clutter during the winter, saving the final pruning until later in the Spring, when they hope the danger of frost is past.

Obviously, that’s a very labor intensive approach, and not every vineyard can double prune. But we’re managing some 225 vines, and they can be pruned in a couple of days. So, we can afford to wait.

So that’s our approach for this year, and probably every other year going forward. If February is the new April, then procrastination is our new friend.

Category: All Posts, Virginia Vineyards Association, Viticulture