Horticulturist says plant for cold

Horticulturist William L. MacKentley would like to throw a pail of ice water on the U.S. Department of Agriculture’s updated plant zone maps.

“I think it’s a little over optimistic,” he said. “We’re still one of the coldest parts of the lower 48.”

The USDA released a map last month revised from 1990 that showed warming trends across the nation, including the north country.

Gardeners use zones as an indicator of whether a plant will survive winters where they live.

Zones are divided by 10-degree ranges, with the lower numbers indicating colder regions. Each zone is subdivided into 5-degree ranges. Zone 4A has a minimum temperature of 30 below, while Zone 4B has a minimum temperature that is 5 degrees higher.

The map for the north country eliminated much of Zone 3B, tempting gardeners who live in deep frost pockets to buy plants they might only have dreamed of in the past.

That is what big-box stores that sell nursery stock are hoping, so that gardeners become perennial shoppers, returning year after year for trees and flowers that stand a good chance of dying and have to be replaced, Mr. MacKentley said.

“It’s pandering to the industry,” said Mr. MacKentley, co-owner with his wife, Diana M., of St. Lawrence Nurseries in Potsdam, which specializes in cold hardy fruit trees and plants.

North country gardeners, he said, have to be realistic about where they live.

“It’s our geography that defines us. Yes, warming is taking place, but it’s taking place over the long haul. We may be as hot as Georgia in the summer in 2050, but that doesn’t mean we won’t have a cold snap in the winter,” he said. “Plant it as though it were 3B and be happy if you get warmer.”

Years when the temperature dropped to about 50 below, considered test winters, are not that far behind us. They took place in 1980-81, 1970, 1956, 1948, and 1933-34.

Gardeners are better off being a bit conservative, he said.

“That doesn’t mean I won’t keep trying to grow peaches,” Mr. MacKentley said.