2012 USDA Plant Hardiness Map
The USDA has released a new version of its plant hardiness zone map. You may be in a new zone, but this is no reason to upset your gardening plans
Radio interview source: Kim Kaplan, Spokeswoman, Agricultural Research Service, USDA
The USDA's plant hardiness zone map is a way for you to assess whether a plant will survive in your area. It's based on the average annual minimum winter temperature, divided into 10-degree Fahrenheit zones. The map was updated in January 2012, the first time in 22-years.
Kim Kaplan is a spokeswoman for the USDA's Agriculture Research Service. She says technology has allowed for more precise mapping. The accuracy scale is now about a-half-mile-square.
"In this map, we have a very sophisticated algorhythm that takes into account a lot of different factors and weights them," she says. "Such as elevation, slope of land, prevailing winds, the nearness to large bodies of water, all of which are going to affect the weather. By using that equation, we are able to get a lot more accuracy to the map."
There are no straight lines that separate one zone from another anymore. They intertwine. Kaplan says you and your neighbors may now be in different zones. However, that the new map is only a guide.
"Nothing is going to supplant the knowledge a gardener has of his or her own garden," says Kaplan. "You know where that low spot is, where the frost pools first, the warm spot in front of that south-facing white wall where you can push your zone. You need to have a good idea of where you are within your zone, how close you are to the next zone, so that you can balance the risk against the expense of losing a plant."
What has grown in your garden before the new map came out will probably continue to grow there. Kaplan says there is no reason to rip out your plants just because a map says your zone has changed.
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