August is a transitional month, offering a significant opportunity to inject immediate color or establish plants that will thrive in subsequent years. This late-summer window allows gardeners to capitalize on warm soil temperatures for root growth and secure the best varieties before they sell out.
Annuals for Late Season Color
The fastest way to revive a tired summer garden is by planting quick-maturing annuals from nursery stock for late-season color. These flowers complete their life cycle within one season, providing bloom until the first hard frost. Planting varieties that handle both heat and cooler nights ensures a display that bridges the gap between summer and fall.
Heat-loving annuals like Zinnia and Celosia are excellent choices, thriving in the lingering warmth of August and blooming prolifically. Zinnias produce bold flowers that attract pollinators and benefit from regular deadheading. Celosia, also known as cockscomb, provides unique texture with its plumed or crested flowers in vibrant shades of red, orange, and yellow.
For color in containers or as a groundcover, Petunias and Marigolds are reliable transplants for August. Petunias, especially spreading varieties, quickly fill space and maintain a high bloom count when kept consistently watered. Marigolds are valued for their cheerful gold and orange tones, often flowering until a killing frost ends the season.
Perennials and Biennials for Next Year
August is an advantageous time to establish perennial and biennial plants because the soil is still warm. This warmth is conducive to rapid root growth, allowing plants to build a strong foundation before winter forces dormancy. Planting now provides a critical head start for the following year’s bloom.
Perennials such as Echinacea (coneflower), Coreopsis, and Sedum are excellent candidates for August planting. Echinacea is a sturdy, pollinator-friendly flower that focuses its energy on root development this season, leading to a more robust display next summer. Sedum, especially ‘Autumn Joy,’ is highly drought-tolerant and establishes quickly to provide late-season texture and color.
Biennials like Digitalis (foxglove) are also best planted or sown in late summer, as they require a period of chilling to flower in their second year. Planting early in the month allows these plants to develop sufficient foliage and root mass to successfully overwinter. This ensures a full and vigorous bloom in the future.
Planting Spring Blooming Bulbs
While the peak season for planting most spring-blooming bulbs is in the fall, August is the time to finalize planning, order stock, and begin site preparation. Bulbs like Daffodils, Tulips, and Hyacinths require cold temperatures, or chilling, to initiate flower formation. Purchasing these bulbs now secures preferred varieties before they sell out and allows time for proper storage until the soil cools.
An exception is the Autumn Crocus, which can be planted in August and will flower the same year. For true spring bloomers, preparation should focus on ensuring the planting location has excellent drainage, as bulbs are susceptible to rot in soggy conditions. Incorporating organic matter into the soil now will improve texture and drainage before the bulbs are settled in the ground later in the season.
Ensuring Success in August Heat
The high temperatures and intense sun of August require specific techniques to ensure new plantings survive. The most important practice is deep and infrequent watering, which encourages roots to grow downward, seeking moisture. Aim to provide one to one-and-a-half inches of water per week, soaking the soil thoroughly rather than just misting the surface.
Watering should be done during the cooler parts of the day, specifically early morning or late evening, to minimize water loss through evaporation. Applying a two to four-inch layer of organic mulch around all new plants is also beneficial. Mulch acts as an insulating layer, regulating soil temperature and reducing evaporation, keeping the root zone cooler and consistently moist.
Before planting, amend the soil with compost to increase its capacity to retain moisture and nutrients. This organic matter helps buffer the plant’s roots against the stress of high temperatures and dry conditions. Finally, place new transplants and seeds into the ground during the cooler morning or evening hours, allowing them time to acclimate before facing the midday sun.