Sunflower in Zone 6A — Great Plains

Sunflowers are a fantastic addition to any Great Plains garden. Their towering height and bright blooms bring cheer, and you can harvest the seeds for a tasty snack or leave them for the birds. Plus, they're surprisingly easy to grow in our prairie soil.

Our region is known for extreme weather, including periods of drought and the occasional hailstorm. But with careful timing and a little planning, you can absolutely enjoy a bountiful sunflower harvest within our 188-day growing season.

Starting sunflower seeds indoors is an option, but direct sowing is generally preferred since they grow so quickly. If you're eager to get a head start, especially in the northern Plains where the growing season can feel shorter, you can start seeds indoors from late March through mid April, about three weeks before you plan to transplant. Use seed trays filled with a good seed-starting mix, and keep them warm and well-lit.

Bottom watering is a good way to keep the seedlings consistently moist without overwatering. Given our variable spring weather, starting indoors can give you a bit of extra control. Just remember that sunflowers develop a strong taproot, so use larger pots to avoid transplant shock.

Transplant your sunflower seedlings outdoors from late April through mid May, once the risk of a hard frost has passed. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings common in the Plains.

Space the seedlings 18-24 inches apart to give them plenty of room to grow. Keep an eye on the weather forecast – a late-season frost can still happen, so be ready to cover your young plants if needed.

Direct sowing is the easiest and most common way to grow sunflowers in the Great Plains. Sow seeds from mid April through mid July, ensuring the soil temperature is at least 60°F. Choose a sunny spot with well-drained soil.

Prepare the soil by loosening it and adding some compost or other organic matter. Plant the seeds about 1 inch deep and space them 18-24 inches apart. Water gently but thoroughly after planting.

Sunflowers germinate quickly and grow rapidly, so you'll see sprouts in no time. Thin seedlings if needed to ensure proper spacing. With full sun and consistent moisture, your sunflowers will thrive.

Sunflowers are moderately drought-tolerant once established, thanks to their deep taproot. However, consistent watering is crucial, especially during the seedling stage and during flowering. In the Great Plains, where rainfall can be unpredictable, it's important to monitor soil moisture.

During the hot summer months, from late June through August, aim to water deeply about once a week, providing about 1 inch of water. Use the "finger test" – stick your finger into the soil about 2 inches deep. If it feels 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 low-to-moderate humidity.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, indicated by yellowing leaves and a generally unhealthy appearance. Mulching around the base of the plants helps retain moisture and suppress weeds.

You can expect your first sunflower harvest from early July through mid October, depending on when you planted and the specific variety. For harvesting seeds, wait until the back of the flower head turns brown and the seeds are plump and starting to loosen. You might need to cover the heads with netting to protect them from birds!

To harvest the seeds, cut the entire flower head off the stalk, leaving about a foot of stem. Hang the heads upside down in a dry, well-ventilated place to dry completely. Once dry, you can easily remove the seeds by rubbing the flower head. For cut flowers, harvest when the petals first open.

As the first frost approaches in mid- October, harvest any remaining flower heads that are close to maturity. You can bring them indoors to finish ripening.

Here are three common problems you might encounter with sunflowers in the Great Plains:

Birds Eating Seeds

• What it looks like: Sunflower heads with missing or pecked-at seeds. Birds may be actively feeding on the plants.
• What causes it: Birds are attracted to sunflower seeds as a food source.
• How to fix/prevent it: Cover the sunflower heads with netting or paper bags once the seeds start to mature. You can also try using bird deterrents like reflective tape or scarecrows.

Sunflower Moth

• What it looks like: Small, cream-colored moths fluttering around the sunflower heads. You may also see larvae (small caterpillars) feeding on the seeds and flower parts.
• What causes it: Sunflower moths lay their eggs on the developing flower heads, and the larvae hatch and feed on the seeds.
• How to fix/prevent it: Monitor your plants regularly for signs of infestation. Remove and destroy any infested flower heads. You can also try using 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: 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.

Great Plains Specific Challenges: The hot heat and variable rainfall in the Great Plains can stress sunflowers, making them more susceptible to problems. Be sure to provide adequate water during dry spells and choose varieties that are well-suited to our climate. Wind protection is also essential to prevent tall sunflowers from toppling over.

Sunflowers make great companions for several plants in the Great Plains garden. Cucumbers and squash benefit from the shade provided by the tall sunflowers, which helps keep their soil cool and moist. Green beans can climb up the sunflower stalks, saving space and providing support. Corn can benefit from the wind protection offered by sunflowers. Lettuce enjoys the partial shade during the hottest part of the day.

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