Sunflower in Zone 6B — Midwest

Sunflowers practically scream "summer" and are a rewarding addition to any Midwest garden. Their cheerful faces bring joy, plus you can harvest the seeds for snacking or roasting, or enjoy them as cut flowers. The good summer heat we get here really helps them thrive.

While our Midwest weather can be unpredictable, especially with those summer heat spells and occasional severe storms, sunflowers are surprisingly resilient. With our fertile soil and a growing season that lasts from mid-April to mid-October, you have plenty of time to get a great harvest.

While sunflowers do best when direct-sown, you can start them indoors from late March through mid April if you want a head start, especially if you're aiming for earlier blooms. Use seed trays or small pots filled with a good seed-starting mix. Keep them warm and provide plenty of light, either with a grow light or a sunny windowsill.

Bottom watering is a good idea to prevent damping-off. Just set the tray in a shallow dish of water and let the soil absorb it from the bottom. Given our moderate-to-late springs here, this can give your plants a jump on the season.

Transplant your sunflower seedlings outdoors from late April through mid May, after the danger of frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of shade, increasing the time and sun exposure each day.

When planting, space them 18-24 inches apart. Keep an eye on the weather forecast, because we sometimes get a late frost that could damage tender seedlings.

Direct sowing is the easiest and most common way to grow sunflowers in the Midwest. Sow seeds from mid April through mid July. After our last frost, the soil temperatures are warm enough for quick germination.

Choose a sunny spot with fertile soil. Prepare the soil by loosening it and adding some compost. Plant seeds about 1 inch deep and space them 18-24 inches apart. Water well after planting. Sunflowers are known to grow quickly.

Sunflowers need moderate watering, but they're also drought-tolerant once established, thanks to their deep taproots. During the initial growth stages, water regularly to encourage strong root development. Aim for about 1 inch of water per week, whether it comes from rain or your hose.

Use the "finger test" to check the soil moisture. Stick your finger about 2 inches deep into the soil near the base of the plant. If it feels dry, it's time to water. Water deeply at the base of the plant, rather than overhead, to minimize the risk of fungal diseases in our moderate-to-humid climate.

During our summer heat spells, you might need to water more frequently. Wilting leaves are a sign of underwatering, while yellowing leaves can indicate overwatering. A layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is especially helpful in our wet-summer conditions.

You can expect your first sunflower harvest from early July through mid October, about 80 days after planting. For seeds, wait until the back of the flower head turns brown and the seeds are plump and starting to loosen.

Cut the entire head off the stalk, leaving a foot or so of stem. For cut flowers, harvest when the petals are just starting to open. As we approach our first frost around mid- October, harvest any remaining heads, even if they're not fully mature. You can hang them upside down in a dry, well-ventilated place to finish ripening.

Here are some common problems you might encounter growing sunflowers in the Midwest:

Birds Eating Seeds

• What it looks like: Missing seeds from the flower head, damage to the developing seeds.
• What causes it: Birds are attracted to the seeds as they ripen, especially in late summer and early fall.
• How to fix/prevent it: Cover the flower heads with netting or burlap bags once the petals start to fade. You can also try using bird deterrents like shiny tape or scarecrows.

Sunflower Moth

• What it looks like: Small caterpillars inside the flower head, webbing, and damaged seeds.
• What causes it: Sunflower moths lay their eggs on the developing flower heads, and the larvae feed on the seeds.
• How to fix/prevent it: Inspect flower heads regularly and remove any caterpillars you find. You can also use insecticidal soap or Bacillus thuringiensis (Bt) as a preventative measure.

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.
• 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.

Midwest Specific Challenges: Our moderate-to-hot heat and moderate-to-humid humidity, combined with wet-summer rainfall, can create ideal conditions for fungal diseases like downy mildew. Good air circulation and proper watering techniques are essential for preventing these problems.

Sunflowers are good companions for cucumbers, squash, and green beans. The tall sunflowers can provide shade for the lower-growing cucumbers and squash, while beans can help fix nitrogen in the soil. Corn also benefits from the support of sunflowers. Lettuce can be planted at the base of sunflowers, taking advantage of the partial shade during our hotter summer days.

Avoid planting potatoes near sunflowers, as they can compete for resources and attract similar pests.