Frost hits Ontario apple blossoms

Monday, May 12, 2008

By MARIBETH FITTS

Speaking at an apple information day held at the Horticultural Experimental Station, Simcoe on May 8, John Cline said that temperatures at that location dipped to about –4ºC in the early morning hours of April 30 and held at the low temperatures with little or no wind for about three hours.

Apple growers attending the meeting reported blossom damage ranging from negligible to 75 per cent depending on the growing area. Greater damage has been seen in low spots of orchards and fields further away from the moderating effects of the large lakes.

Gary Ireland, who grows 85 acres of apples on his farm near Simcoe, estimated between 50 and 75 per cent damage on his king blooms that were at the pink stage (just prior to first bloom), when the frost hit.

Apple blossoms are affected by cold temperatures differently depending on their stage of development, explained Cline. Trees in full bloom will suffer greater damage than those at green tip or pink. At full bloom, apple blossoms can be killed by –3.9º C while buds at first pink can withstand up to –4.4ºC.

Cline also noted blossoms in the upper canopy of the orchards are more likely to survive than those close to the ground because of cold air settling. This difference can often make fruit thinning more of challenge for growers, he said.

The amount of fruit that actually set will become evident in the next few weeks. It only takes about 10 percent fruit set to make a marketable crop on apple trees, he said. BF