A May frost caused damage to crops in Norfolk County
Temperatures on May 17 and 18 fell below the freezing mark for the low, hitting -0.7˚C on May 17 and -2.1˚C on May 18 at the Delhi weather station. Exact temperatures varied across the county.
At that point in the season when the frost hit, most vegetable crops were either not planted or hadn’t come up yet. Apples and ginseng did have some damage done.
Hayden Dooney, general manager of the Norfolk Fruit Growers Association, didn’t believe there was considerable damage, but apples were in bloom at the time of the frost.
“I’m sure there’s some out there but I haven’t observed it,” he said.
Typically, he said if the temperature hits -2˚C, there is a 10 per cent loss. In this case, he said growers were lucky. “We were right at the threshold,” he said.
Many growers have either irrigation or frost fans to keep the temperatures in the orchard from dropping below freezing. For instance, Dooney has four fans on his 40-acre orchard. With the fans operating, the temperature didn’t dip below 1.5˚.
“There was frost on the ground, but not on the apples,” he said.
With warm air rising and cold air settling, the fans mix the two air temperatures to keep frost from forming on the blossoms.
Rebecca Coates, executive director of the Ontario Ginseng Growers Association, said there were widespread reports of frost. She didn’t have an estimate of the quantity of the frost damage at press time, but did predict it would impact yield.
Association researcher Amy Shi explained frost can lead to the kinking of the ginseng stem above the straw.
“If the damage occurs to seedlings, they do not usually recover. Older plants can somewhat recover later in the season,” she explained. “If the plants are damaged by frost, there will be a higher chance of foliar diseases with conditions favourable to the disease, such as Alternaria and Botrytis.”
There were reports of damage to asparagus, but the extent couldn’t be quantified before press deadline.