August is a transitional period, marking the final stretch of summer heat while offering the ideal window for planning next year’s blooms. The lingering warmth encourages rapid root development, which is beneficial for nearly all plant types. Strategic planting in August secures immediate, vibrant color through the fall season. This timing is also necessary for establishing a robust foundation for spring flowers, maximizing the garden’s productivity across two distinct seasons.
Flowers for Immediate Late-Summer and Fall Display
To ensure color until the first hard frost, select established transplants rather than starting from seed. These plants already have developed root systems and can dedicate energy to flowering immediately. Heat-tolerant annuals are the most reliable option for flourishing in the late-summer environment.
Celosia, with its brightly colored flower heads, thrives in intense heat and humidity. Gomphrena (Globe Amaranth) produces small, clover-like blossoms resilient to dry conditions and blooms profusely. Late-season Zinnia varieties offer large flowers that attract pollinators and maintain visual impact into cooler autumn weather.
Classic fall staples, such as Garden Mums (Chrysanthemum) and Asters, should be planted in August for proper establishment before peak bloom. When selecting Mums, look for plants with mostly closed buds, indicating a longer potential bloom time. Mums are “short-day” plants, meaning decreasing daylight hours naturally trigger their flowering response.
Asters (Symphyotrichum species) are late-season performers that provide a food source for migrating butterflies. These perennials offer daisy-like flowers in shades of purple, blue, and white, blooming as other summer plants fade. Ornamental Cabbage and Kale are also planted now for their intensely colored foliage, providing sustained fall and winter interest.
Flowers and Bulbs to Plant for Spring Blooms
The warm soil temperatures of August create an ideal environment for establishing plants that require dormancy before blooming. Planting perennials now allows their root systems to grow deep and wide before the ground freezes. This extensive root growth powers a strong, healthy flush of flowers when the plant emerges in the spring.
Perennials like Coneflower (Echinacea), Sedum (Stonecrop), and Rudbeckia (Black-Eyed Susan) can be successfully transplanted in August. Sedum is resilient to late-summer heat and its flower heads offer structural interest that lasts through the winter. Planting perennial Salvia now gives them time to establish a robust framework for a more prolific bloom next year.
August is the time to sow seeds for biennials and hardy annuals that require vernalization (a cold period) to initiate flowering. Biennials such as Foxglove (Digitalis purpurea) and Hollyhocks (Alcea rosea) are sown now to grow a foundational rosette of leaves this year. They must be established enough to survive winter before flowering dramatically next spring or early summer.
Hardy annuals and short-lived perennials, including Pansies and Violas, can be sown in late August. This early start results in larger, more substantial plants compared to spring-sown varieties, often yielding blooms in the fall that return early in the spring. While major spring-blooming bulbs like Tulips and Daffodils are planted in September or October, August is the time to purchase them and prepare the soil.
Successful Planting Techniques for Summer Heat
Mitigating transplant stress during August requires techniques focused on reducing water loss and cooling the root zone. Adjusting the timing of planting directly influences recovery. Transplanting new flowers in the late afternoon or early evening is preferable, allowing the plant a full night of cooler temperatures to settle in before facing the next day’s sun.
Before placing the plant, thoroughly water the hole itself, creating a moisture reservoir beneath the root ball. Saturating the container an hour or two before planting ensures roots are hydrated and less brittle. After planting, deep, slow watering is superior to light sprinkling, encouraging roots to grow downward toward stable moisture deeper in the ground.
Soil preparation is important for August planting, as amending the soil improves water retention. Incorporating organic matter, such as compost or well-rotted manure, increases the soil’s capacity to hold moisture around the roots. This helps buffer the roots from temperature fluctuations and prevents the soil from compacting too tightly.
Immediately apply a thick layer of organic mulch, approximately two to three inches deep, to provide an insulating barrier against the intense sun. Mulch keeps the soil cool and reduces surface water evaporation. For sensitive transplants or during a heatwave, temporary shading using a shade cloth or a chair during the hottest part of the afternoon reduces the risk of transplant shock.