Hardiness Zones Revisited
Earlier this year, the U.S Department of Agriculture introduced a new version of its Plant Hardiness Zone Map – a useful tool for gardeners and researchers that was last updated in 1990. The map divides the United States, including Puerto Rico, into 13 separate zones representing regions of minimum average winter temperatures. Each zone is a 10-degree Fahrenheit band that is further divided into five-degree half-zones. Zone boundaries in the new map have shifted in many parts of the United States and two new zones, 12 (50-60 degrees Fahrenheit) and 13 (60-70 degrees), have been added. The new map is generally one five-degree Fahrenheit half-zone warmer than the previous map throughout much of the United States, but some areas shifted to cooler zones rather than warmer ones.
Viewer Tip: The Plant Hardiness Zone Map can help the nearly 80 million gardeners in the United States prepare for spring. Learn your hardiness zone by entering your zip code or clicking on the map at http://planthardiness.ars.usda.gov/PHZMWeb/#. Knowing your hardiness zone will help you use catalog and plant descriptions to choose garden plants that will thrive in the area where you live. Even if your zone has changed in the new map, the plants you have in your yard will most likely continue to thrive – but you may also be able to introduce some new plants to your garden.
Planning a vegetable garden? There are several types of vegetable seeds that can germinate at surprisingly cold temperatures. Visit https://attra.ncat.org/attra-pub/summaries/summary.php?pub=20 to find out the optimum soil temperatures for growing a range of vegetables.
(Source: U.S. Department of Agriculture, “USDA Unveils New Plant Hardiness Zones,” http://www.ars.usda.gov/is/pr/2012/120125.htm and “Plant Hardiness Zone Map,” http://planthardiness.ars.usda.gov/PHZMWeb/#)