Thursday, February 16, 2012

2012 USDA Hardiness Zone Map by Carol King

Exciting news for all you plant nerds! On Jan. 25, 2012 the U.S. Department of Agriculture  released the new version of its Plant Hardiness Zone Map,  updating a useful tool for gardeners and researchers for the first time since 1990. The new map (developed by USDA's Agricultural Research Service and Oregon State University's PRISM Climate Group)—is available online at  Long-awaited changes in the climate zone guide show northward warming trends, while also targeting a few colder areas in the mountains.

Hardiness zones are based on the average annual extreme minimum temperature during a 30 year period in the past. It is not based on the lowest temperature that has ever occurred in the past or might occur in the future. Each zone is based on 10 degrees Fahrenheit. Two new zones were added in hotter climates this year for a total of 13 zones.

The USDA web site ( is now inter active.  Just put in your zip code and you can see where your garden is zoned.
This  map might give gardeners a chance to try some borderline plants that might not have been hardy in the past. For instance,  my Lakewood garden was Zone 5 and is now Zone 6A.   Zone 5 was -10 to -20;  Zone 6A is -5 to -10;  not too big of a change but the thrill seeker in me just might try to develop a microclimate to winter-over some of the more tender perennials!