Gardeners and landscapers rely on climate classifications to determine which plants can survive the typical weather patterns of a specific location. These classifications organize vast geographic areas into zones based on long-term weather data. Understanding these zones is an effective way to select species that will successfully grow without requiring extensive protection from temperature extremes. Identifying the specific climate classifications is a necessary first step toward developing a successful landscape in the Memphis, Tennessee, area.
Memphis’s USDA Plant Hardiness Zone
Memphis, Tennessee, is officially classified within the United States Department of Agriculture (USDA) Plant Hardiness Zone 8a. This designation comes from the 2023 update to the USDA Plant Hardiness Zone Map, which uses 30-year averages of the coldest annual temperatures to define the zones. The Zone 8a classification indicates that the average annual extreme minimum temperature for the area falls between 10°F and 15°F.
This represents a change from the previous 2012 map, which had Memphis largely located in Zone 7b, a slightly colder designation. The shift reflects a general trend of milder winter temperatures in the region, affecting the 30-year average used in the latest analysis. This zone number and its corresponding temperature range determine which perennials, shrubs, and trees can reliably survive the Memphis winter.
Applying the Zone to Planting Decisions
The Zone 8a designation provides a clear guideline for selecting plants that are rated to withstand temperatures down to 10°F. When purchasing perennial plants, gardeners should look for a hardiness rating of Zone 8 or lower, such as Zone 7 or Zone 6, to ensure winter survival. Selecting species rated for a colder zone provides an extra margin of safety against unusually harsh or prolonged cold snaps.
Plants designated as “tender” may not survive the winter outdoors in Zone 8a and would require winter protection or replacement the following spring. Perennials rated specifically for Zone 8a may benefit from a layer of protective mulch over the root zone during the coldest months. The 8a designation signals that annual vegetables and flowers can typically be planted earlier in the spring and survive later into the fall compared to colder zones. The average last frost date is generally in late March, allowing for an extended growing season.
Understanding the AHS Heat Zone
While the USDA zone addresses a plant’s tolerance for winter cold, the American Horticultural Society (AHS) Heat Zone Map addresses its tolerance for summer heat. This secondary classification is particularly important for Southern climates like Memphis, where prolonged high temperatures can stress or kill plants. The AHS system uses the average number of days per year when the temperature exceeds 86°F (30°C).
Memphis typically falls into a heat zone that experiences between 91 and 120 days annually with temperatures above this 86°F threshold. Gardeners must select varieties known to perform well under these conditions to prevent issues like wilting, scorching, or a cessation of flowering and fruiting. Consulting both the USDA and the AHS zones allows for a more comprehensive approach to plant selection.