A new federal climate map has made official what some experienced gardeners already knew -- warmer-weather plants are coming to Long Island.

The U.S. Department of Agriculture's latest update to its Hardiness Zone Map, which breaks the continental United States into 11 regions according to their average coldest day, has bumped both Nassau and Suffolk counties up a temperature zone.

That means the Island is now considered warm enough for some plants once thought to be too fragile for Northeastern winters.

Want to plant a blossoming crape myrtle as a low-maintenance alternative to ornamental cherry trees? No problem anymore.

Bushy camellias, with blooms as large as five inches in diameter, could become as common in suburban lawns as the peony.

"It will be a very slow process, but eventually you will see additions to the plant palette," said Paul Brand, nursery sales representative at Bissett Nursery in Holtsville.

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While regional gardeners said they have been aware of a warmer trend for years, the new maps will likely give less-experienced gardeners the confidence to try plants previously associated with more southern climates, and nurseries will be more likely to stock them, several agricultural experts said.

"A lot of people are trying plants from warmer climates already and finding they are surviving the winters," said Alexis Alvey, nursery and landscape specialist at the Cornell Cooperative Extension of Suffolk County. "This really makes it official, and people don't have to worry about winter injury as much on certain plants."

The new map puts most of Suffolk and northern Nassau in a zone where the average lowest temperature of the year ranges from 0 to 5 degrees Fahrenheit. Southern Nassau and New York City are in a zone where the average lows range from 5 to 10 degrees.

The old map, last updated in 1990, indicated the region's coldest day ranged from -5 to 0 degrees and from 0 to 5 degrees, Alvey said.

At Brookhaven National Laboratory, the average monthly minimum temperature between 1990 and 2010 was 1.9 degrees higher than the temperature between 1970 and 1990.

The new map is more accurate than the one produced in 1990, said Chris Daly, the Oregon State professor of engineering who developed the mathematical model used to produce the map. It draws from 30 years of data, compared with only 13 for the 1990 version and includes such factors as proximity to water or elevation.

This more-precise information has allowed the department to create a searchable web-based map that gardeners can use to find the zone they live in, at planthardiness.ars.usda.gov/


Dorothy Titus, a gardener with the Locust Valley Garden Club, welcomed the new details.

"Gardening is a crapshoot," she said. "Something might work for here and not down the block. Knowledgeable gardeners should be aware of what their requirements are when they go to the nursery." Frederick B. Soviero, director of grounds and landscaping at Hofstra University, said the new map would make it easier to educate novice gardeners about plant selection.

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He also enjoyed the idea of a warmer climate.

"I can grow more stuff," he said. "That's how I like it."