June marks the definitive start of deep summer in Tennessee, shifting the gardening focus entirely to crops that thrive in intense heat and humidity. The state generally falls within USDA hardiness zones 6b through 8a, meaning the risk of frost is long gone, and soil temperatures are now consistently high. This period is for maximizing the growth of warm-season varieties that will mature before the first predicted frost in the fall. Embracing this timing allows gardeners to achieve a second, substantial harvest and fill in any gaps from early spring planting failures.
Direct-Sow and Transplant Vegetables Suited for June
June is the ideal time to sow seeds directly into the garden for warm-weather annuals that germinate best in high soil temperatures, often exceeding 70°F. Crops that dislike root disturbance will quickly sprout and produce a continuous harvest through late summer.
Direct-Sow Crops
- Bush and pole beans, which provide a continuous harvest through late summer.
- Okra and summer squash (including zucchini and pattypan varieties), which offer rapid growth and production within 50 to 60 days.
- Corn, especially quick-maturing varieties that will finish before the fall cool-down.
- Sweet potatoes, by setting out slips, as these require the full duration of summer’s heat to develop underground tubers.
- Black-eyed peas and other southern peas, which are highly heat-tolerant legumes.
June is also a suitable time to set out transplants for a late-season yield of solanaceous crops. A second wave of pepper and eggplant seedlings can be planted, as these fruits require significant heat to set and ripen. Late-season tomato transplants can be installed now to ensure a fresh supply of fruit that avoids the peak disease pressure that often impacts early-planted crops in August. It is best to choose determinate or short-season varieties for this late planting window to ensure they mature before the autumn frost arrives.
Flowers, Herbs, and Ornamental Additions
The high temperatures of June are perfectly suited for establishing a variety of heat-loving annual flowers. Heat-tolerant annuals such as zinnias, marigolds, and vinca (Catharanthus) can be planted now to withstand the intense afternoon sun without wilting. Angelonia and portulaca are two other options that excel in containers and beds, offering a sustained display of blooms that can tolerate dry, hot soil conditions.
June is an excellent month for establishing perennial herbs that prefer warm, well-drained soil, ensuring they have sufficient time to develop a robust root system. Basil, a classic warm-season herb, can be planted from transplants or seed now and will produce fragrant leaves quickly for culinary use. Mediterranean herbs such as rosemary, thyme, and oregano also benefit from the warm conditions, as they are naturally adapted to environments with high heat and lower moisture. Planting these herbs now ensures a steady supply of fresh cuttings for summer cooking and allows the plants to get fully established before winter dormancy.
Managing High Summer Heat and Humidity
Successful June planting depends heavily on mitigating the stresses of Tennessee’s high summer heat and humidity, starting with strategic watering practices. Deep, infrequent watering is more effective than daily shallow applications, as it encourages plant roots to grow deeper, making them more resilient to drought. Watering should be done in the early morning hours to minimize water loss from evaporation and reduce the risk of fungal diseases. Utilizing drip irrigation or soaker hoses focuses water directly to the root zone, maximizing efficiency.
Mulching the garden beds is a simple yet powerful technique for managing soil temperature and moisture retention during hot spells. A layer of organic mulch, such as shredded bark, pine straw, or compost, applied two to four inches thick helps insulate the soil, keeping the root zone cooler and more stable. This barrier reduces the rate of water evaporation from the soil surface, meaning plants require less frequent watering. It also helps to suppress weed growth, reducing competition for water and nutrients.
Amending the soil with quality organic matter is important for plants established in June, as summer rains can leach nutrients quickly. Incorporating compost or a balanced, slow-release fertilizer into the planting hole helps improve the soil’s capacity to both drain excess water and retain sufficient moisture during dry periods. Vigilance is required against increased pest and disease pressure, which is common in warm, humid conditions. Regularly inspecting the undersides of leaves and ensuring good air circulation between plants are proactive measures that help maintain plant health throughout the summer.