Gardening 101

New USDA Plant Hardiness Map

There’s a new USDA Plant Hardiness Zone Map—and it’s worth investigating. About half of all the zones in the country moved a half-zone warmer than they were on the previous map.

Most of the Triangle has moved from Zone 7a to Zone 7b, which is no surprise to most gardeners here. The map confirms what many of us already knew: we can now grow plants that we were unable to grow fifteen years ago. It also means that certain plants requiring a number of chilling hours may no longer perform as well for us.

This is important information for a gardener. If you want a shrub, perennial, or tree to survive and grow year after year, the plant must tolerate conditions in your area, such as the lowest and highest temperatures and the amount and distribution of rainfall. If you see a hardiness zone listed in a plant catalog or on a plant tag, chances are it refers to the USDA map.

Check out the new online interactive map. Place your cursor over a state and an enlarged picture emerges showing all the counties, making it easier to pinpoint an exact location and its hardiness zone.

The map now divides North America into 13 separate zones; each zone is 10°F warmer (or colder) in an average winter than the adjacent zone. This is the first time since 1990 that the United States Department of Agriculture has updated the map.

Source: Kit Flynn