Washington Warming to Southern Plants

"Certainly, part of it is attributable to the increase in greenhouse gases," said Jay Lawrimore, who oversees climate monitoring for the National Oceanic and Atmospheric Administration. "But then there's natural variability as well." This week, for example, meteorologists have said the region's unusually warm weather could be linked to the natural atmospheric phenomenon El Niño.

As dramatic as the Washington area's shift was, it probably won't mean a rash of crashing timber. Local horticulture experts said many of the area's most popular species -- maple, oak and river birch -- will still tolerate higher temperatures.

The biggest effects are likely to come on the extreme ends of the spectrum: Such species as the Colorado blue spruce, native to places colder than Washington has ever been, could be under stress. Such species as needle palms, native to the southeastern United States, could do better.

"The trees are not going to die, and you shouldn't go out and cut anything down," said Nelson, of the Arbor Day Foundation. "We're saying . . . now that we've got a warmer climate, consider different trees."

In interviews yesterday, some area gardening experts said they had already seen the effects of warmer weather. At the Montgomery cooperative extension office, horticulture specialist Chuck Schuster said that crape myrtles were doing better than he had ever seen.

"It was something that I would never consider planting" years ago, Schuster said. "But now they're thriving."

Some people see a bright side to this trend: It could bring more options for planting.

"Whenever you get warmer, that's a good thing," said Lenny Martinko, general manager at the American Plant Food store in Bethesda.

But at the Botanic Garden, McLaughlin had mixed feelings. He was glad to find that such species as the needle palm or the yaupon, a holly native to areas farther south, could be raised more easily. But then, he said, he thought of the impact on the species that belong here: native plants that might find their growing seasons shifted, their life cycles out of sync with pollinating insects, if warming trends continued to affect them.

"It's exciting, in a way," he said. "It's alarming, when you look at native plant communities."