Planting annual flowers in August gives late-season color, fills empty spots, and sets up extended blooms into fall. Whether you’re in a warm southern zone or a cooler northern region, there are great options you can still plant. August planting depends on your USDA hardiness zone, but many annuals thrive when planted in late summer. Below is a guide to 10 easy-to-grow annual flowers, along with tips for planting and care based on your zone.
Know Your Zone Before Planting
Before you dig in, it’s important to know your USDA hardiness zone. Zones 3 to 5 have shorter seasons and cool quickly, while zones 6 to 9 stay warm into fall. In cooler zones, you’ll want fast-blooming varieties that can handle a light frost. In warmer zones, you can plant heat-loving annuals that thrive well into October and even November.
Calendula (Zones 3–9)
Calendula, also known as pot marigold, is a cool-season annual that thrives when planted in August in zones 3 to 7. In zones 8 and 9, plant it later in the fall for winter color.
To grow calendula, choose a spot with full sun and well-draining soil. Sow seeds directly into the ground or containers and keep the soil evenly moist. Germination happens quickly, and blooms follow within 6–8 weeks. Deadhead spent flowers regularly to encourage constant blooming.
Zinnia (Zones 4–9)
Zinnias are one of the fastest-growing annuals and ideal for August planting, especially in zones 6 to 9. They bloom within 6 to 8 weeks from seed and thrive in the late-summer heat.
Plant zinnia seeds directly in full sun. Make sure the soil is loose, well-drained, and rich in organic matter. Water at the base of the plants to avoid powdery mildew. Zinnias bloom profusely until the first frost, especially when deadheaded often.
Nasturtium (Zones 3–9)
Nasturtiums grow quickly and bloom in under two months, making them perfect for late-summer planting in all zones. In zones 3 to 6, they provide fall color before frost. In zones 7 to 9, they bloom well into late fall.
Plant seeds directly in the ground or in pots. Choose a sunny location, but they will tolerate partial shade. Avoid rich soil, which reduces blooms. Water regularly, and harvest flowers and leaves for edible garnishes and salads.
Alyssum (Zones 3–9)
Sweet alyssum loves cooler weather, so August is a good time to sow it in zones 3 to 7 for fall blooming. In zones 8 and 9, plant it now for winter and spring color.
Scatter seeds over prepared soil in full to partial sun. Keep the soil moist until germination, which happens quickly. These low-growing plants form soft, fragrant mounds and can be used to edge beds, containers, and borders.
Marigold (Zones 4–9)
Marigolds grow fast from seed and are perfect for warm August gardens in zones 6 to 9. In zones 4 and 5, use nursery starts for quicker blooms.
Sow seeds or plant transplants in full sun and rich, well-draining soil. Water deeply but allow the soil to dry slightly between watering. Remove faded flowers to keep blooms going until frost. Marigolds also repel pests, making them great companion plants for fall veggies.
Cosmos (Zones 5–9)
Cosmos are heat-tolerant and bloom quickly from seed, making them ideal for August planting in zones 5 through 9. They grow tall and provide airy, daisy-like flowers that bloom into fall.
Plant seeds directly in full sun and well-drained soil. Once established, cosmos need little watering and thrive in poor soil. Deadhead blooms or let them self-seed. These flowers attract pollinators and make excellent cut flowers.
Petunia (Zones 6–9)
Petunias are often thought of as spring flowers, but they can be planted again in late summer in warmer zones. In zones 6 through 9, planting nursery-grown petunias in August will provide vibrant blooms well into fall.
Choose a sunny location with fertile, well-draining soil. Space plants about 10–12 inches apart and water regularly. Fertilize with a balanced liquid fertilizer every two weeks to keep them blooming nonstop. Deadhead spent blooms for best results.
Impatiens (Zones 6–9)
Impatiens grow quickly and can be added to shaded spots that need late-season color. Plant nursery starts in August in zones 6 to 9 for long-lasting blooms through fall.
Use rich, moist soil and plant in partial to full shade. Water often, especially during hot weather. Add mulch to keep the soil cool and moist. Fertilize every two weeks with a low-nitrogen fertilizer to promote flowers over foliage.
Salvia (Zones 6–9)
Salvia loves heat and sun, and it thrives in late-summer gardens. In zones 6 to 9, plant it in August for bold color that lasts into fall. Choose annual types like Salvia splendens or Salvia coccinea for quick blooms.
Plant in full sun with well-drained soil. Water when the soil feels dry, and fertilize once a month. Deadheading will keep flowers coming. Salvias also attract hummingbirds and butterflies, adding more life to your garden.
Cleome (Zones 6–9)
Also called spider flower, cleome grows fast and adds height and texture to August gardens. In zones 6 to 9, direct sow seeds or use transplants to get blooms through fall.
Choose full sun and well-drained soil. Cleome is drought tolerant once established. Space plants 12–18 inches apart to give them room to spread. Flowers appear within 6 to 8 weeks from seed and attract pollinators throughout the season.
Tips for Planting Annuals in August
To succeed with late-season planting, prepare your soil well. Start by loosening it and mixing in compost or a balanced organic fertilizer. Water new plantings thoroughly, especially during hot August days. Mulch helps keep roots cool and moist. For seeds, keep the soil surface evenly damp until germination.
Use containers or raised beds if your soil is too hard or compacted. Containers also allow you to move plants into sheltered areas if frost threatens early. Choose annuals that grow quickly and don’t need a long time to bloom. Always check the seed packet or plant label for days to maturity and match that with your zone’s average frost date.
Extend Bloom Time into Fall
If your goal is fall color, choose annuals that can take light frost or keep blooming through shorter days. Deadheading—removing spent blooms—will keep many annuals producing new flowers. You can also mix cool-season veggies like kale or Swiss chard into beds with your flowers for added interest.
In zones 7 to 9, many of these annuals will bloom into November. Even in zones 3 to 6, fast growers like nasturtiums, calendula, and alyssum can brighten beds until a hard freeze.
Final Thoughts
Planting annual flowers in August adds fresh life and color when summer gardens start to fade. With the right selections for your USDA zone, you can enjoy blooms for weeks or even months. Use quick-growing flowers like zinnias, marigolds, or cosmos for vibrant color. In shady spots, plant impatiens or alyssum. If you live in a cooler zone, stick with faster bloomers like calendula or nasturtium. With a little planning and care, your late-summer garden can look stunning all the way into fall.
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