Yes, Virginia gardeners, it really is getting warmer

We don't need a color-coded map to tell us the temperatures are rising, particularly this winter.

Though the 8a plant hardiness zone for most of Hampton Roads did not change in the U.S. Department of Agriculture's recently released updated and color-coded map, we just feel that the weather is getting warmer.

And we're right.

The USDA has found that across the country in most areas, the climate is warming, whether or not it has risen enough to shift areas into a new climate zone.

In some parts of the country, the temperature has risen as much as 5 degrees since the last climate map was issued in 1990.

On the other hand, our very warm winter is probably an anomaly, but it still gives us an idea of what could be in the offing in years to come if the warming trend continues.

The most obvious are the daffodils, forsythia and other early spring bloomers that are coming in now. Their premature arrival could change blooming patterns this spring.

The climate zone map is important to gardeners because it tells them which plants will thrive in which areas, said Susan French, Virginia Beach's city arborist.

"It's what all seed companies use as guidelines and what plant ID books use too," she said.

Gardeners here rely on the fact that they are in zone 8a. They use that designation for purchasing their plants and seeds, and that has not changed this time around.

But just across the Chesapeake Bay, most of the Eastern Shore, except for the northernmost part, was boosted from zone 7a into zone 8a, just like the rest of Hampton Roads.

The National Arboretum in Washington, D.C., suggested that Eastern Shore gardeners now might want to try growing, say, common olive or loquat, trees that tolerate the 8a zone. The new plant zone maps were unveiled at the arboretum in January.

Zone 7a represents an average annual minimum temperature between 5 and 10 degrees, while zone 8a represents an average annual minimum temperature of 10 to 15 degrees, according to the USDA.

And though the temperatures here have not risen enough in this area to boost us into the next zone - 8b, which includes the North Carolina Outer Banks - who knows what will happen before the next climate change maps are issued?

French believes the area can look forward to several possible subtle changes. We may be able to grow different varieties of plants because of the warmer winter, for example. For French that means that her plumbago, a pretty blue flower that looks like phlox, may do better.

"Some years I can get it through the winter and some not," she said. "So it's my indicator."

On the other hand, warmer weather can spell trouble too, she said. It may bring more invasives into our area, French said. Plants like kudzu vine may start creeping in. Fire ants have already arrived in limited amounts. For dog owners, fleas and ticks may be harder to control as the insects continue to reproduce through the winter.

"Be aware of invasive plants that may grow through the winter," she said. "Things may not go dormant as they normally do."

Warmer winters also mean hotter summers, so some plants we take for granted here may not tolerate the heat in the future. French wonders, for example, if hotter summers might take a toll on Japanese maples.

"It's not just warmer winters," she said. "It's warmer everything."

Along with warmer temperatures come other issues that gardeners will have to learn to grapple with, including more rain and a rise in sea level.

Mary Reid Barrow,

barrow1@cox.net