If you've ever read a gardening book or browsed through a seed catalog, you've likely seen a reference to "zones." Technically known as plant hardiness zones, they're sometimes called climate zones, planting zones, or gardening zones. Knowing your hardiness zone is helpful when planning and purchasing plants for your yard or garden. Most plants and seeds indicate the hardiness zone on their packaging so you can confirm if they will likely survive in your area.
Understanding USDA Hardiness Zones
The USDA plant hardiness zones are determined by the average annual minimum winter temperature, with each zone representing a 5-degrees Fahrenheit section of minimum temperatures. There are 13 total zones, though most of the United States fits between zones 3 and 10. The higher the zone's number, the warmer the climate.
Hardiness zones are intended as guidelines rather than hard and fast rules. While they can tell you if a plant is likely to survive, it does not mean that it's guaranteed. Many factors are involved in a plant's success, including precipitation, shade level, plant genetics, soil quality, and more.
Tennessee USDA Hardiness Zones
Tennessee is comprised of seven USDA hardiness zones: 5a, 5b, 6a, 6b, 7a, 7b, and 8a. Northern areas in zone 5b experience the state's lowest temperatures dipping to minus 15 degrees Fahrenheit. Mountain City, the northeasternmost county seat in Tennessee, is located in zone 6a where the lowest temperatures of the year drop to minus 10 degrees Fahrenheit.
Memphis is in both 7a and 7b and extreme winter temperatures can drop to 0 degrees Fahrenheit. This area typically experiences the last frost-free date in the spring by April 15 and the last frost-free date in the fall on October 30, though those dates can vary up to two weeks.
While Tennessee weather differs across the state, overall it's a generally temperate climate with all regions experiencing four distinct seasons. Many plants (except tropical varieties) thrive in this southern state due to extended growing seasons and ample rainfall. While zones in the mountains can experience significant snowfall, winters, in general, tend to be mild compared to the northern states.
Tennessee Crops and Gardening
Tennessee is a great place to grow fruits and vegetables, including broccoli, squash, cucumbers, strawberries, green beans, and cantaloupe. Fruit trees (except citrus) also do well in most areas of the state with apples, pears, peaches, and plums being the most common varieties. Farmland covers 44 percent of Tennessee, with the main crops being soybeans, cotton, corn, tobacco, and greenhouse and nursery plants.
Some annual flowers for zones 5–8 are marigolds, impatiens, snapdragons, geraniums, and sunflowers. If you'd rather plant one time instead of every year, you may want to try some native Tennessee perennials. Black-eyed Susans, butterfly weed, foamflower, and crested iris are hardy and low-maintenance choices for your landscaping. If you'd like more information on native Tennessee species, you can find an extensive list at Tennessee Smart Yards.
Updated by Holly Whitfield November 2017