The success of any garden begins with knowing the local climate and the specific timing for sowing seeds or setting out young plants. Tennessee’s varied geography creates diverse microclimates, meaning planting advice must be tailored to your specific location within the state. From the Mississippi River lowlands in the west to the mountainous terrain of the east, a successful planting season relies on understanding your region’s unique seasonal windows. This guide provides a practical framework for gardeners across the state to determine what to plant and when.
Understanding Tennessee Hardiness Zones and Frost Dates
Tennessee spans a considerable range of growing conditions, categorized by the USDA Plant Hardiness Zone Map. The state generally falls between zones 6a and 8a, reflecting a difference of up to 20 degrees Fahrenheit in the average annual extreme minimum winter temperature. The coldest zones, 6a and 6b, are found in the higher elevations of the Cumberland Plateau and the Great Smoky Mountains. Conversely, the warmest zones, 7b and 8a, are located in the southwestern corner, especially around the Memphis area in West Tennessee.
Gardeners must identify their specific zone because it dictates which perennial plants can reliably survive the winter lows. Beyond the hardiness zone, the most important dates for annual planting are the last expected spring frost and the first expected fall frost. These dates define the state’s frost-free growing season, which averages about 190 days. The last spring frost can occur as early as the first week of April in western areas, but may not pass until the first week of May in the higher-elevation central and eastern parts of the state.
Warm Season Crops, Herbs, and Flowers
Warm-season crops thrive in Tennessee’s humid subtropical climate and must not be planted until all danger of a late spring frost has passed. These plants are sensitive to cool soils and air temperatures, requiring consistent warmth to germinate and grow. Gardeners should wait until the soil temperature stabilizes above 60 degrees Fahrenheit before planting these heat-loving varieties.
Many popular summer vegetables are best started indoors several weeks before the last frost and then transplanted into the garden. Tomatoes, peppers, and eggplants need a long, warm season to produce a substantial harvest, making transplanting the most effective method for this region. These plants will be severely damaged or killed by any temperature drop below freezing. Basil is a similarly sensitive herb that flourishes when transplanted after the soil is thoroughly warm.
Other warm-season vegetables perform best when their seeds are sown directly into the prepared garden soil. Direct seeding is preferable for crops that develop a deep taproot or those that germinate quickly under warm conditions. This group includes squash varieties, such as zucchini and butternut, as well as corn and beans. Okra is another excellent direct-sow option that requires very warm soil, often planted about a month after the last frost date.
A variety of flowers that tolerate high heat and humidity can also be planted once the weather warms. Popular annuals like zinnias and marigolds provide season-long color and thrive in the same conditions as warm-season vegetables. These flowers are generally easy to grow from seed, though transplants are used to achieve an earlier blooming display. Keeping the soil consistently moist during establishment is important to manage the intense summer heat.
Cool Season Vegetables and Fall Bulbs
The gardening season extends beyond summer with a second planting window focused on cool-season vegetables and plants meant for the following spring. These crops are planted in late summer or early fall to mature during the cooler months, as they prefer mild temperatures and can withstand light frosts. The timing for a fall harvest is determined by counting backward from the first expected fall frost date, which usually falls between late October and mid-November across Tennessee.
To maximize the fall harvest, leafy greens should be planted in late summer. Kale and leaf lettuce can be sown from seed from July through early September, allowing time to reach maturity before hard freezes arrive. Root vegetables, including carrots and radishes, also thrive when planted in late summer, growing best in the cool soil temperatures of autumn. These fall-planted crops often benefit from being started indoors during peak summer heat and then transplanted.
For gardeners anticipating spring blooms, fall is the necessary time to plant bulbs that require a cold period to initiate flowering. Spring-blooming bulbs like tulips, daffodils, and crocuses should be planted when the soil temperature has dropped to around 60 degrees Fahrenheit, typically from late September to early November. Planting during this window allows the bulbs to establish a strong root system before the ground freezes. A final fall task is setting out garlic cloves in October or November to overwinter and be harvested the following summer.