Sunflower in Zone 7B — Southeast

Sunflowers are a fantastic addition to any Southeast garden. Their bright, cheerful faces bring joy, and the seeds are delicious roasted or used for birdseed. Plus, they're excellent for attracting pollinators, which is always a win in our gardens.

Our long summer and reliable rainfall here in Zone 7B make growing sunflowers relatively easy. We do have to keep an eye out for humidity-related issues and pests like Japanese beetles, but with a little planning, you can enjoy these beauties from early summer through late fall, thanks to our 235-day growing season.

While sunflowers thrive when direct-sown, starting them indoors can give you a head start, especially if you're aiming for earlier blooms. This makes sense if you want to harvest seeds as early as possible. Start seeds indoors from late February through mid March, about three weeks before you plan to transplant them.

Use seed trays or small pots filled with well-draining potting mix. Keep them warm and provide plenty of light – a sunny window or grow lights work well. Bottom watering helps prevent damping-off, a common issue in our moderately humid Southeast springs.

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

When transplanting, space them 18-24 inches apart to allow for adequate growth. Keep an eye on the weather forecast, as a late frost can still occur during this time.

Direct sowing is the easiest and most common method for growing sunflowers in the Southeast. Sow seeds from mid March through early August, ensuring the soil temperature is at least 60°F. Sunflowers germinate quickly in our warm spring soil.

Prepare the soil by loosening it and adding compost or other organic matter. Plant seeds 1-2 inches deep and space them 18-24 inches apart. Water thoroughly after planting and keep the soil consistently moist until seedlings emerge.

Sunflowers are drought-tolerant once established, thanks to their deep taproot, but they still need consistent watering, especially during our hot and humid summers. During the spring, with its frequent afternoon thunderstorms, you may not need to water at all some weeks. Let the rain do its job!

A good rule of thumb is to water deeply but infrequently, aiming for about 1 inch of water per week, especially during hot, dry spells. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. Water at the base of the plant 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 root rot, indicated by yellowing leaves and a mushy stem base. Mulching around the base of the plants with straw or wood chips helps retain moisture and suppress weeds.

You can expect your first sunflower harvest from early June through early November, depending on when you planted. For harvesting seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose.

Cut the entire flower head from the stalk, leaving about a foot of stem. Hang the heads upside down in a well-ventilated area to dry completely. For cut flowers, harvest when the petals first open.

As the first frost approaches in early November, harvest any remaining flower heads, even if they're not fully mature. You can still extract some seeds, or leave the heads out for the birds to enjoy.

Here are some common problems you might encounter with sunflowers in the Southeast:

Birds Eating Seeds

• What it looks like: Missing seeds from the flower head, often with signs of pecking.
• What causes it: Birds are attracted to the seeds, especially as they ripen.
• 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 decoys.

Sunflower Moth

• What it looks like: Small caterpillars feeding on the developing seeds, often accompanied by webbing and frass (caterpillar droppings).
• What causes it: Sunflower moths lay their eggs on the flower heads, and the larvae burrow into the seeds.
• How to fix/prevent it: Remove and destroy any infested flower heads. Apply Bacillus thuringiensis (Bt) to control the larvae. Encourage beneficial insects like parasitic wasps.

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.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides 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. Monitor your plants closely and take preventative measures to ensure a healthy and abundant harvest.

Sunflowers benefit from companion planting. Cucumbers and squash provide ground cover, helping to retain moisture and suppress weeds, which is crucial in our hot climate. Green beans fix nitrogen in the soil, benefiting the sunflowers' growth. Corn provides a natural trellis for climbing sunflowers. Lettuce, planted at the base of the sunflowers, enjoys the partial shade during our long summer days.

Avoid planting potatoes near sunflowers, as they compete for the same nutrients in the soil, hindering the growth of both plants.