— Dan Boyer has plenty of bees pollinating the blossoms in the hundreds of apple trees in his Ridgetop Orchards. His concern is that those blossoms could be killed by a freeze or hard frost during the next five weeks.

Boyer, of Fishertown, and fruit growers across the region are keeping an eye on the Canadian jet streams as they watch their potentially profit-laden trees burst into blossom two to three weeks earlier than normal.

So far, those jet streams bringing with them hard frost and freezing temperatures have not materialized. But May promises to be long and stressful for the growers.

“Right now, we’re in fine shape. We have good bee flight. Pollination is going on fine. We’re cautiously optimistic,” Boyer said last week.

Historically, most apple varieties start blooming in the last week of April or first week of May. But for Boyer and others, those blossoms exploded two weeks ago, prompted by the warm temperatures of early April.

Growers have another three weeks of anxiety before the chance of hard frost is reduced, said Jim Sellmer of the Penn State School of Horticulture.

“We’re two weeks or so ahead of schedule, depending on where you are located. As a standard, the end of fear of a frost is about May 15,” he said, adding there can be frosts as late as Memorial Day.

For the owners of Airesman’s Orchard, Edie Road, Somerset, frost is a concern until the end of  May, evidenced by the apple crop they lost after the fruit had formed.

“In 2002 we had apples the size of a nickel. The freeze was so hard, we had no crop,” said owner Allan Airesman.

What’s going on in the region is being repeated in many East Coast states and in some respects nationwide, said Todd Hultquisk, spokesman with the U.S. Apple Association, a trade association based in Vienna, Va.

“All of the apple growing regions are a little ahead. It’s been a little precarious,” he said.

“There’s been a number of close calls for Pennsylvania and New Jersey.”

While most U.S. growers have been fortunate so far this year with crop loss minimal, the same is not true for apple growers in China, where an early spring brought on blossoms nipped by freezing weather, he said.

Scott Stephens, a meteorologist with the National Climatic Data Center in Asheville, N.C., said while the East was weathering one of the toughest winters on record, the Plains were unseasonably warm.

“We had a very harsh winter and a very abrupt end of winter. A lot of it is because of the warm air from the Plains,” he said.

Stephens urged caution, especially to those farmers and gardeners eager to get crops and plants into the ground.

“It could be a case of fool’s gold. Don’t do anything until the traditional end of the frost season,” he said. “There will probably be a return to more traditional weather with frost or freeze.”

Potential fallout from the early spring and premature blooming could be twofold, according to two of the experts.

“The real question is what the growing season will turn into,” said Sellmer. “They’re creating sugars. They’re demanding moisture. If we stay dry as we are now, there will be a need for more moisture.”

On a more positive note, early development of the apples may mean the 2010 crop will be in the markets earlier than normal, said Karen Rodriguez, of the Pennsylvania Apple Marketing Board.

“It  may push harvest ahead of schedule because we’re so far ahead, but it’s too early to tell,” she said.

For Boyer and Airesman, their concern is immediate – getting through the next month.

Airesman is keeping his fingers crossed.

Boyer has heaters to attach to tractors that he will pull around the orchard, warming the air and hopefully fending off any killer cold.

Because there is frost on the ground does not mean it reaches the apple blossoms, he said of a temperature differential of as much as five degrees from the grass to the branches.

Even having temperatures below 32 degrees does not mean crop loss, he said.

“As long as it stays above 28 degrees, we’ll be fine. The plants have sugar in them and that helps,” he said.

But when it comes to freezing, a few degrees can make a world of difference.

If the temperatures dip to 28 degrees and hold for a half hour the crop loss is about 10 percent, Boyer said. If it drops to 25 degrees, there can be 90 percent crop kill off.

“This (early bloom) has created a lot of anxiety for us,” he said.