Growers watch and wait for weekend deep freeze

February 10, 2016 | St Catharines Standard | Bill Sawchuk

Grape growers and wineries will be watching the thermometer this weekend as a deep freeze is forecast for Niagara.

Brock University’s Cool Climate Oenology and Viticulture Institute issued a warning to Ontario wineries to be ready to take whatever precautions they can.

The Grape Growers of Ontario estimate the total overall economic impact of the grape and wine industry in the province at $3.3 billion.

“We will see what happens,” Brock University scientist Jim Willwerth said. “Right now, the temperatures would be borderline where we could see potential damage to vines. You are always concerned because if the forecast isn’t accurate, it could be colder, and you have to error on the side of caution and be prepared."

“They will be preparing for the weather and seeing if they need the wind machines.”

The wind machines are used warm up the air, so the vines never experience the cold temperatures in the surrounding area.

The fans mix the air. Air that is about 20 metres above the ground is about 5°C to 7°C warmer than ground level. The fans mix warmer air with the colder air at ground level, which in turn elevates the ground temperature above the point at which damage occurs.

One machine covers about 10 to 15 acres of grapes. The machines are about 35-feet high and cost about $35,000. The also cost $60 to $75 an hour to run.

“Compared to what we have gone through the last two winters, I’m not too worried about this weekend,” Sue-Ann Staff, of Sue-Ann Staff Estate Winery in Lincoln, said. “Concern starts to grow when it gets down to about minus-20, and it stays that way for a sustained period, and that’s not what the forecast says.

“We are lucky. We don’t have the fans here. The topography of our property has rolling hills and the cold air just seems to keep on moving and rolls down the escarpment.

“Where the land is flat, the air can start to settle out on a star-filled night, and the heat escapes to the atmosphere. That’s where the damage begins to occur.”

Brock University runs a Vine Alert service, which gives growers and wineries updated information on the current state of different varieties of buds during the winter. The growers use the information to make decisions about how best to protect their crops.

“So far the winter has been kind,” Willwerth said. “Right now the vines are looking good. We need calm air this weekend. If it is windy, we can’t use the machines because we don’t have the temperature inversions. And you also can’t run the wind machines when it is windy. It’s not safe.”

Temperatures are expected to dip to -16°C during the day Saturday and -19°C at night. Sunday the forecast calls for -10°C during the day and -14°C at night. The winds are expected to be in 30 km/h range Saturday before falling off Sunday.

“One saving grace for this weather event is that it is getting colder gradually,” Willwerth said. “It isn’t going from plus-20 to minus-20 overnight so the vines can adapt.

“The thing about farming is you try and mitigate the risks as much as possible with the proper varieties and innovative tools like wind machines — but, in the end, there is always going to be risk.”