The USDA Plant Hardiness Zone Map helps gardeners determine which plants can survive winter temperatures in a specific location. This system divides North America into zones based on the average annual minimum winter temperature. Knowing this zone is important because it dictates whether a perennial plant, shrub, or tree will survive the coldest part of the year. Zones range from 1 (coldest) to 13 (warmest), and selecting plants labeled for your zone or a lower number increases the chance of successful perennial growth.
Tallahassee’s Specific Hardiness Zone
The city of Tallahassee, Florida, is officially designated as USDA Plant Hardiness Zone 9a. This is an update from the previous designation of Zone 8b, reflecting recent temperature data and indicating a warming trend. This shift expands the variety of plants that can reliably survive the winter outdoors.
Zone 9a means the area experiences an average annual extreme minimum temperature range of 20°F to 25°F. The zone system is divided into 10-degree increments, and the letter suffix further divides that increment into 5-degree segments. The “a” suffix denotes the colder half of the zone.
Interpreting the Zone Designation
The hardiness zone number directly corresponds to the lowest winter temperature expected over a long period. Perennial plants labeled for Zone 9 are expected to withstand temperatures down to 20°F without needing extensive protection. This temperature threshold is the primary factor the USDA map uses to determine plant survival.
The zone designation sets the limits for perennial growth by establishing the plant’s cold tolerance. A plant rated for Zone 8, for instance, can tolerate temperatures down to 10°F, meaning it will likely thrive in Zone 9a. However, a plant rated for Zone 10, which can only tolerate temperatures down to 30°F, would be at high risk of being killed by an average Tallahassee winter. The hardiness zone only addresses cold tolerance and does not account for summer heat or humidity.
Practical Planting Recommendations
Tallahassee’s subtropical climate, characterized by mild winters and long, hot, humid summers, requires selecting plants that can endure both the occasional freeze and the prolonged heat. The last expected frost date is typically around mid-March, and the first frost is usually in late November, providing a lengthy growing season for both cool-season and warm-season crops.
Trees and Shrubs
The area supports classic Southern varieties like the Southern Magnolia (Magnolia grandiflora) and the Crepe Myrtle (Lagerstroemia indica). Native, heat-tolerant options for Zone 9a include the Wax Myrtle (Morella cerifera) for screening and the Red Buckeye (Aesculus pavia), which attracts hummingbirds. These selections are resilient and handle the local soil and weather conditions.
Vegetable Gardening
A dual planting strategy is effective, rotating between cool-season and warm-season crops. Cool-season vegetables (such as cabbage, broccoli, and lettuce) are best planted in the fall (September through November) for a winter and early spring harvest, allowing them to mature before the summer heat causes them to bolt.
Warm-season vegetables, including tomatoes, peppers, corn, and squash, should be planted from February through April once the risk of frost has passed.
Flowers and Ornamentals
Perennial flowers and annuals that tolerate the intense summer sun and humidity are necessary for continuous color. Reliable choices include heat-loving perennials like Salvia, Coneflower (Echinacea), and Daylily (Hemerocallis), as well as sun-tolerant annuals such as Vinca and Pentas.