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Dallas-area gardeners have known for years the region is warmer than its official status as USDA Zone 7. The government acknowledged the fact on Jan. 25 with the release of its updated Plant Hardiness Zone Map.

Central Dallas � that is, Dallas roughly south of LBJ Freeway � was considered Zone 8a for more than a decade by local garden experts. The new map shows all of Dallas and north to the Red River as Zone 8a.

An update of the official guide for 80 million gardeners reflects a new reality: The coldest day of the year isn�t as cold as it used to be.

In Zone 8a, the "average annual extreme minimum temperature," based on data from 1976 to 2005, is 10F to 15F degrees. However, the map does not measure how hot it gets, a factor in Texas that is just as relevant, if not more so, to a plant�s survival.

For instance, the Outer Banks of North Carolina and northeastern Oregon also are Zone 8a.

Gardeners can register their ZIP code at planthardiness.ars.usda.gov and their zone will pop up.

USDA spokeswoman Kim Kaplan, who was part of the map team, repeatedly tried to distance the new zones in the map from global warming issues. She said even though much of the country is in warmer zones, the map "is simply not a good instrument" to demonstrate climate change because it is based on just the coldest days of the year.