The U.S. Department of Agriculture's (USDA) Plant Hardiness Zone Map reflects average low temperatures and allows gardeners to know which annuals and perennials can survive and thrive in their regions. For many gardeners, the temptation is high to choose beautiful plants that do not fit within the appropriate hardiness zone. However, plants that are not labeled to grow within your hardiness zone will never grow as well and will require a lot of extra attention. To achieve the healthiest, most beautiful garden, only select plants that are labeled to match your hardiness zone.
In January 2012, the USDA and Oregon State University released a new Plant Hardiness Zone Map, which provides gardeners and scientists with average low temperatures over a thirty year time frame. The new map categorizes each area of the Unites States into zones (1 to 13), with each zone reflecting a ten degree low temperature difference. Additionally, each zone has two sub categories (a and b) to note five degree temperature differences.
The new Plant Hardiness Zone Map shows category changes for many regions compared to the old map, because the new map averages a longer and more recent time period and takes into account additional data such as elevation changes, nearness to bodies of water, and expert analysis. Since many regions have experienced a zone change, it is important to check your region on the new map to make sure you are using the most up-to-date data and giving your garden the best chance of survival.
Keep in mind, while most seed packages will not show the updated map until 2013, the hardiness information shown can still be used to choose appropriate plants. If a seed packet states the plant is hardy in zones 4-6, this reflects a plant that is hardy in extreme low temperatures from -30 degrees Fahrenheit to zero degrees Fahrenheit. If your region falls within those temperatures on the new map, the seeds are okay to plant in your region regardless of which map is shown on the package.
- U.S. Department of Agriculture