Sunflower in Zone 8A — Southeast

Sunflowers are a fantastic addition to any Zone 8A garden here in the Southeast. Their bright blooms bring cheer, and the seeds are delicious roasted or used for birdseed. Plus, they're surprisingly easy to grow in our long summer, adding vertical interest to your garden beds.

We do have to contend with the humidity and summer heat, which can lead to some disease pressure. But with a little planning and attention to timing, you can enjoy a beautiful sunflower crop during our 245-day growing season.

While sunflowers thrive when direct sown, you *can* start them indoors if you want a jump start, especially for succession planting. Start your seeds late February through mid March, about three weeks before you plan to transplant. Use seed trays or small pots filled with a good seed-starting mix.

Keep the soil consistently moist, and provide warmth and plenty of light – a sunny windowsill or grow lights work well. Bottom watering is a great way to keep the seedlings happy. Remember that spring here in the Southeast can be variable, so keep an eye on the weather as transplant time approaches.

Transplant your sunflower seedlings outdoors late March through mid April. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Choose a sunny spot with well-draining soil, and space your plants 18-24 inches apart. Keep an eye on the weather forecast for any late-season cool snaps that can set back young plants.

Direct sowing is the easiest and most common way to grow sunflowers here in the Southeast. Sow your seeds mid March through mid August for a continuous supply of blooms. Sunflowers are quick growers, so you can stagger your plantings every few weeks.

Prepare your soil by loosening it and adding some compost. Sow the seeds about an inch deep, spacing them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge. Soil temperatures need to be at least 60°F for good germination.

Sunflowers are moderately drought-tolerant once established, thanks to their deep taproot. However, consistent watering is key, especially during our hot and humid summers. The best approach is to water deeply but infrequently, allowing the soil to dry out slightly between waterings.

Stick your finger about two inches deep into the soil. If it feels dry, it's time to water. During the hottest part of the summer, you might need to water once or twice a week, providing about an inch of water each time. With our humid climate, it's best to water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, so watch out for yellowing leaves and a soggy soil. A good layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is helpful in our climate.

You can expect your first sunflower harvest early June through mid November, about 80 days after planting. For sunflower seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose. Cut the entire head off the stalk and allow it to dry in a well-ventilated area.

If you're growing sunflowers for cut flowers, harvest them when the petals first open. Cut the stem at an angle and place the flowers in water immediately. As our first frost approaches around mid- November, harvest any remaining flower heads, even if they're not fully mature, and allow them to dry indoors.

Sunflowers are generally easy to grow, but here are a few common problems we see in the Southeast:

Birds Eating Seeds

• What it looks like: Sunflower heads with missing or damaged seeds. You might see birds actively pecking at the seeds.
• What causes it: Birds are attracted to the ripening seeds.
• How to fix/prevent it: Cover the flower heads with netting or paper bags once the petals start to dry. You can also try using bird deterrents like reflective tape or scarecrows.

Sunflower Moth

• What it looks like: Small caterpillars inside the sunflower head, feeding on the seeds. You might also see webbing or frass (caterpillar droppings).
• What causes it: Sunflower moths lay their eggs on the developing flower heads.
• How to fix/prevent it: Inspect your sunflower heads regularly for signs of infestation. You can handpick the caterpillars or use an organic insecticide like Bacillus thuringiensis (Bt).

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. Different species affect different plants.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Southeast Specific Challenges: Our hot, humid summers and wet-summer rainfall create ideal conditions for fungal diseases like downy mildew. The humidity also makes sunflowers more susceptible to pests like sunflower moths. Regular monitoring and proactive measures are key to keeping your sunflowers healthy and productive in our climate.

Companion planting can help your sunflowers thrive. Cucumbers and squash benefit from the sunflower's shade, which helps keep the soil cool and moist. Green beans provide nitrogen to the soil, which sunflowers need for healthy growth. Corn can act as a windbreak, protecting the sunflowers from strong winds. Lettuce can be planted under the sunflowers to take advantage of the shade during the hottest part of the day.

Avoid planting potatoes near sunflowers, as they can compete for nutrients and water.