Sunflower in Zone 6B — Mid-Atlantic

Sunflowers are a fantastic addition to any Mid-Atlantic garden. Their cheerful blooms brighten up the humid summers, and you can harvest the seeds for a healthy snack or leave them for the birds as winter approaches. Plus, they make excellent cut flowers and are a great way to attract pollinators to your garden.

While we do have our share of gardening challenges here in Zone 6B, like deer pressure and the occasional Japanese beetle, the long 198-day growing season gives you plenty of time to grow beautiful sunflowers. Just watch for late frost in the spring and you'll be rewarded with impressive blooms.

Starting sunflower seeds indoors isn't essential, since they transplant best by direct sowing, but it can give you a head start. If you want to get a jump on the season, start seeds indoors from mid-March through early April, about three weeks before you plan to transplant them outdoors. Use seed trays filled with a good seed-starting mix, and keep them in a warm spot with plenty of light.

Bottom watering is key to preventing damping off, especially with our moderate Mid-Atlantic spring weather. Simply set the tray in a shallow dish of water and let the soil absorb the moisture from the bottom. This encourages strong root growth.

Transplant your sunflower seedlings outdoors from mid-April through mid-May, after the danger of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

When transplanting, space the seedlings 18-24 inches apart to give them plenty of room to grow. Keep an eye on the weather forecast; those unexpected late-season cold snaps can still happen in the Mid-Atlantic, so be ready to cover your young plants if necessary.

Direct sowing is the easiest and most reliable way to grow sunflowers in our region. Sow seeds directly into the garden from early April through late July, giving you a long window of opportunity. Sunflowers are quick growers, so even a late sowing can produce blooms before our first frost.

Choose a sunny spot with well-drained soil. Before sowing, loosen the soil and amend with compost. Ensure the soil temperature is at least 60°F (16°C) for best germination. Plant seeds about 1 inch deep and space them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge.

Sunflowers are drought-tolerant once established, but they still need regular watering, especially during our humid Mid-Atlantic summers. Newly planted sunflowers need consistent moisture to develop a strong root system. Aim to water deeply but infrequently, allowing the soil to dry out slightly between waterings.

During the peak of summer heat, check the soil moisture regularly. Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Generally, established sunflowers need about 1 inch of water per week, whether from rainfall or irrigation. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Wilting leaves are a sign of underwatering, while yellowing leaves can indicate overwatering. A good layer of mulch around the base of the plants helps retain moisture, suppress weeds, and regulate soil temperature. Straw or shredded leaves work well in our region.

Your first sunflower harvest will likely be from late June through late October, depending on when you planted. Sunflowers grown for seeds are ready to harvest when the back of the head turns brown and the seeds are plump and slightly loose. Cut the entire head off the stalk, leaving a foot or so of stem attached.

For cut flowers, harvest when the petals first open, and the flower is showing its color. Cut the stem at an angle and place it immediately in water. As late October approaches and the first frost threatens, harvest any remaining sunflower heads, even if they're not fully mature. You can hang them upside down in a cool, dry place to allow the seeds to finish ripening.

Here are a few common problems you might encounter growing sunflowers in the Mid-Atlantic:

Birds Eating Seeds

• What it looks like: Sunflower heads stripped of seeds, often with birds actively feeding on them.
• What causes it: Birds are attracted to the ripe seeds, especially as other food sources become scarce.
• How to fix/prevent it: Cover the sunflower heads with netting or burlap bags once the petals begin to dry. You can also try using bird deterrents like reflective tape or decoys.

Sunflower Moth

• What it looks like: Holes in the sunflower heads, webbing, and small caterpillars feeding on the seeds.
• What causes it: Sunflower moths lay their eggs on the developing flower heads, and the larvae burrow into the seeds.
• How to fix/prevent it: Inspect flower heads regularly for signs of infestation. Remove and destroy any affected heads. Encourage beneficial insects like parasitic wasps, which prey on sunflower moth 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: An oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. Our humid summers can create the perfect environment for this disease.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around the plants by spacing them properly. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Mid-Atlantic Specific Challenges: The moderate-to-hot heat and humid humidity of our summers can exacerbate fungal diseases like downy mildew. Consistent rainfall can also contribute to these issues. Be sure to provide good air circulation and water at the base of the plants to minimize problems.

Sunflowers make great companions for several garden plants here in the Mid-Atlantic. Cucumber and squash benefit from the sunflowers providing some shade during our hot summers. Green beans can use the sunflower stalks as a natural trellis. Corn and sunflowers are classic companions, as they both thrive in similar conditions. Lettuce can benefit from the partial shade provided by sunflowers.

Avoid planting potatoes near sunflowers. Potatoes are susceptible to some of the same fungal diseases as sunflowers, and planting them together can increase the risk of infection.