July is a transitional month for gardeners, shifting the focus from peak summer harvest to planning for fall. Although the heat can make planting seem counterintuitive, this period is ideal for starting a second round of quick-maturing summer vegetables or sowing seeds for a substantial autumn yield. The challenge is introducing vulnerable new plants into hot soil, requiring a strategy to ensure successful germination and establishment. Working with the heat allows for an extended harvest season well past traditional summer months.
Adapting Your Strategy for Midsummer Heat
Success in July planting requires recognizing that high soil temperatures and rapid moisture loss are the primary obstacles for new seeds and transplants. Plant growth slows significantly when air temperatures consistently exceed 86°F and can halt completely in extreme heat. For instance, soil that is too warm prevents cool-season seeds, like lettuce, from germinating, as they require a maximum soil temperature of around 80°F.
Gardeners must calculate the “days to maturity” backward from the average first fall frost date. Since plants grow more slowly as days shorten and temperatures cool, add one to two weeks onto the listed maturity time for fall crops. This planning ensures crops like brassicas or root vegetables have enough time to mature before a hard freeze. Choosing heat-tolerant or slow-to-bolt varieties is also a fundamental part of this midsummer strategy.
Quick-Maturing Vegetables for a Late Summer Yield
July is the final window for planting many vegetables that will mature before the first frost.
Quick Summer Crops
Quick-succession plants like bush beans are excellent choices for a continuous late-season supply, often ready for harvest in 45 to 60 days from direct sowing. Varieties such as ‘Strike’ or ‘Contender’ thrive in warm soil and can be planted every few weeks for a steady yield into autumn.
Root Vegetables
Root vegetables also fare well with a July start. The initial hot period allows for strong root development before cooler weather sweetens the final product. Beets (50 to 70 days) and carrots (70 to 80 days) can be direct-sown now for a late summer and fall harvest. Radishes are the fastest option, maturing in under 30 days, making them perfect for multiple harvests.
Fall Transplants and Greens
For the primary fall harvest, July is the correct time to start cool-season crops indoors for later transplanting. Brassicas need to be started from seed now to be ready for transplanting approximately six weeks before the first expected fall frost.
Brassicas that should be started indoors include:
- Broccoli
- Cabbage
- Cauliflower
Leafy greens can be direct-sown now, as they are highly frost-tolerant and their flavor improves after a light chill. Heat-tolerant lettuce varieties can be planted in partial shade for baby greens in as few as 28 days.
Flowers and Herbs Suitable for July Sowing
Ornamental plants can be successfully sown in July to refresh garden color and attract pollinators during the late season.
Annuals
Fast-growing annuals are heat-loving flowers that can be scattered directly into the garden for continuous blooms until the first hard frost. These flowers germinate quickly in warm soil and provide vibrant color throughout the late summer and early fall.
Biennials and Perennials
July is a good time to sow seeds for certain biennials and perennials that require establishment before winter. Sowing perennials in midsummer allows the plants to focus on root growth rather than flowering, leading to healthier plants entering dormancy.
Species that can be started now for a strong bloom display the following year include:
- Foxglove
- Sweet William
- Aquilegia
- Delphinium
Herbs
Herbs can be successfully planted from seed or small transplants in July, capitalizing on the warm soil. Heat-loving herbs will flourish in the summer sun, providing abundant leaves for fresh use.
Heat-loving herbs include:
- Basil
- Rosemary
- Oregano
- Thyme
Cilantro and dill are prone to bolting in extreme heat, but they can still be planted now. They will benefit from afternoon shade and consistent moisture to delay flowering until early fall.
Post-Planting Care in High Temperatures
Once seeds or transplants are in the ground, managing the high-temperature environment is crucial for survival.
Watering
Deep, infrequent watering is more effective than light surface sprinkling, as it encourages roots to grow deeper where the soil is cooler and more consistently moist. Apply water directly at the base of the plant in the early morning hours. Allow the moisture to penetrate six to eight inches deep before the high daytime evaporation rate begins.
Mulching
A thick layer of organic mulch is an effective defense against heat stress. Applying three to four inches of straw, shredded leaves, or wood chips around plants insulates the soil, lowering the root zone temperature. Mulch also significantly reduces the rate of water evaporation from the soil surface, conserving moisture for the plants.
Shade and Pest Control
For vulnerable transplants or cool-season crops like lettuce, temporary shade can mitigate the stress of intense afternoon sun. Using a specialized shade cloth, or improvising with a simple sheet, reduces the amount of direct solar radiation the plant receives. This lowers the plant’s temperature and decreases water loss. Finally, summer heat often increases pest pressure. Newly planted areas require daily monitoring for common summer insects, such as spider mites or squash bugs, to manage infestations quickly.