Planting flowers in July and August presents unique challenges due to intense summer heat and drier soil conditions. High temperatures can stress new plantings, demanding careful selection and technique. Despite the heat, this late-summer window is a valuable time for gardeners looking to refresh tired beds or container gardens. This guide offers specific plant recommendations suitable for immediate bloom or long-term establishment during the warmest part of the year.
Annuals and Heat-Tolerant Plants for Immediate Color
For gardeners seeking instant visual payoff, planting established annuals from nursery stock is the most effective approach in July and August. Using small plants already past the seedling stage bypasses the long germination and establishment time required by direct seeding. These transplants have developed a robust root structure, allowing them to focus immediately on producing foliage and flowers. Selecting varieties known for high heat tolerance ensures they will not flag or cease blooming during peak summer temperatures.
Certain annuals thrive under the intense solar radiation and sustained high temperatures of late summer. Zinnias flourish in full sun and are known for their continuous blooming cycle until the first frost, especially when deadheading spent flowers regularly. French Marigolds (Tagetes patula) provide saturated color and generally perform better in the heat than many other bedding plants. Tall, airy Cosmos also maintain their delicate appearance without wilting, provided they are not over-fertilized, which encourages leaf growth over flower production.
Portulaca (Moss Rose) is a succulent-like annual that exhibits extreme drought and heat tolerance, making it ideal for rock gardens or shallow containers that dry out quickly. This plant stores water in its fleshy leaves and stems, requiring minimal supplemental irrigation once established. Excellent drainage is necessary to prevent root rot in heavier soils. Trailing Petunias, especially newer hybrid varieties, are excellent choices for baskets and window boxes where they can cascade freely. These varieties are often self-cleaning, dropping spent blooms naturally, and maintain a vigorous bloom even when air temperatures consistently exceed 90 degrees Fahrenheit.
Perennials and Bulbs for Future Blooms
Planting perennials in late summer offers a significant advantage by allowing root systems to establish before winter dormancy. The warm soil of July and August encourages rapid root growth, anchoring the plant and preparing it to withstand the freeze-thaw cycles of colder months. Establishing strong roots now means the perennial can dedicate its energy to flowering immediately when spring arrives. This approach is more successful than spring planting, where the plant simultaneously tries to establish roots and produce blooms.
Certain perennials planted now will reward the gardener with color sooner, specifically providing fall interest. Upright Sedum varieties, such as ‘Autumn Joy,’ are easily transplanted in summer and produce deep pink to bronze flower heads that last well into November. The mature flower heads also provide winter structure, adding texture to the dormant garden. Fall-blooming Asters benefit from a late-summer planting to ensure they develop enough bulk to support their dense clusters of purple or blue flowers, bridging the gap until the first hard frost.
July and August are the months to begin planning for the following spring by acquiring spring-flowering bulbs. Daffodils (Narcissus), Tulips (Tulipa), and Crocus require a specific chilling period to initiate flower formation. This cold exposure breaks down starches into sugars, fueling the subsequent growth and bloom cycle. Although planting often occurs closer to September or October, purchasing now ensures the best selection and quality. Store these bulbs in a cool, dark, and dry location until the soil temperature drops below 60 degrees Fahrenheit.
Essential Tips for Late Summer Planting Success
The timing of installation is a significant factor in the survival of any plant placed in the ground during peak summer. Planting should occur during the cooler hours of the early morning or late evening to minimize transplant shock caused by midday heat. Immediately after planting, a deep, thorough watering is necessary to settle the soil and eliminate air pockets around the roots. This initial watering should saturate the root ball and surrounding soil to a depth of at least six inches. Providing consistent moisture during the first two weeks is paramount, as the plant cannot rely solely on its undeveloped root system.
Managing soil temperature and moisture retention is important when daytime temperatures are high. Applying a two-to-three-inch layer of organic mulch, such as shredded bark or composted leaves, around the base of the plant is highly beneficial. Mulch acts as an insulating layer that significantly reduces water evaporation from the soil surface. This layer also helps keep the root zone cooler, preventing heat-related stress that can inhibit nutrient uptake. Ensure the mulch does not directly touch the plant stem, as this can encourage rot and harbor pests.
Gardeners should resist the urge to apply high-nitrogen fertilizers to newly planted items during this establishment phase. The focus must be on encouraging root development rather than excessive, tender new foliage susceptible to heat and sun scald. A slow-release, low-phosphorus fertilizer can be used sparingly to support root growth without forcing top growth. Fertilization can resume only once the plant shows clear signs of robust, new growth.