Sunflower in Zone 6A — Southeast

Sunflowers are a fantastic addition to any Southeast garden. Their towering height and bright blooms bring cheer, and the seeds are delicious roasted or enjoyed by birds. Plus, they're surprisingly easy to grow here, providing a long summer of sunny beauty.

We definitely have our share of challenges in the Southeast, like humidity and pests. But with a little planning and attention, you can absolutely grow beautiful sunflowers. Our long growing season, usually around 198 days, gives them plenty of time to mature.

While sunflowers thrive when direct-sown, starting them indoors can give you a head start, especially if you're aiming for an early bloom. Start seeds indoors from mid-March through early April, about 3 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them warm and well-lit – a sunny windowsill or grow light works perfectly.

A little tip I've found helpful is to bottom-water your seed trays. This encourages strong root growth and prevents damping off, which can be a problem in our humid spring weather. Remember that our spring season is moderate, so you want to make sure they get enough sunlight.

Once the danger of frost has passed, usually from mid-April through mid-May, you can transplant your sunflower seedlings outdoors. 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.

When transplanting, space your sunflower plants 18-24 inches apart to give them plenty of room to grow. Keep an eye on the weather forecast – a late cold snap can still happen, so be prepared to cover your seedlings if needed.

Direct sowing is the most common and generally most successful method for growing sunflowers in the Southeast. Sow seeds directly into the garden from early April through late July. This gives you a long window to succession plant for continuous blooms.

Choose a sunny spot with well-drained soil. Sunflowers aren't too picky, but they'll appreciate soil amended with compost. Plant seeds about 1 inch deep and 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge, which usually takes about a week. Since sunflowers grow quickly, direct sowing is ideal for our long summer.

Sunflowers are moderately drought-tolerant once they’re established, thanks to their deep taproots. But regular watering is still important, especially during our hot, humid summers. The key is to water deeply but infrequently.

During the spring and fall, when temperatures are milder, water about once a week if we haven’t had significant rainfall. In the heat of summer, increase that to two or three times a week, depending on how dry the soil is. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week, either from rain or irrigation. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A good layer of mulch around your sunflowers will help retain moisture and suppress weeds. Pine straw or shredded hardwood mulch works well in the Southeast.

You can expect your first sunflower harvest from late June through late October, depending on when you planted. Sunflowers take about 80 days to mature. For seeds, wait until the back of the flower head turns brown and the seeds are plump and somewhat loose.

To harvest the seeds, cut the flower head off the stalk and hang it upside down in a dry, well-ventilated place. You can also cover the head with a paper bag to protect it from birds and pests. For cut flowers, harvest when the petals first open. As our first frost approaches in late October, harvest any remaining flower heads that are close to maturity. You can bring them indoors to finish ripening.

Sunflowers, like all plants, can have problems in the Southeast. Here are a few to watch out for:

Birds Eating Seeds

• What it looks like: Sunflower heads with missing or pecked-at seeds.
• What causes it: Birds are attracted to the ripening seeds, especially as other food sources become scarce.
• How to fix/prevent it: Cover the flower heads with netting or paper bags once the seeds begin to develop. You can also try hanging shiny objects like pie tins or CDs to scare the birds away.

Sunflower Moth

• What it looks like: Webbing and frass (insect droppings) on the flower heads, damaged seeds.
• What causes it: Sunflower moths lay their eggs on the flower heads, and the larvae feed on the developing seeds.
• How to fix/prevent it: Inspect your plants regularly for signs of infestation. Remove any affected flower heads and dispose of them properly. You can also use insecticidal soap or Bacillus thuringiensis (Bt) to control the larvae.

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: Downy mildew is caused by an oomycete pathogen that thrives in cool, humid conditions. It spreads via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around your plants by spacing them properly. 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 encourages pests like sunflower moths. Regularly scout your plants and take preventative measures to minimize these problems.

Companion planting can help your sunflowers thrive in the Southeast. Cucumbers and squash make good companions because they provide ground cover, which helps to suppress weeds and retain moisture in our clay soil. Green beans add nitrogen to the soil, benefiting the sunflowers. Corn provides a natural trellis for climbing sunflowers. Lettuce can be planted around the base of sunflowers to provide shade and keep the soil cool. Avoid planting potatoes near sunflowers, as they can compete for nutrients and increase the risk of disease.