Sunflower in Zone 3B — Great Plains

Sunflowers are a fantastic addition to any Great Plains garden. Their towering height and bright blooms add beauty, and you can harvest the seeds for snacking or roasting. Plus, they're surprisingly versatile in the kitchen and provide a great sense of accomplishment when you harvest your own sunflower seeds.

Our region's extreme weather can be a challenge, but sunflowers are well-suited to our short growing season. With a little planning, you can easily enjoy these beauties within our 118-day window. We just need to keep an eye on any late frosts in the spring and get them going as soon as we can.

Starting sunflowers indoors is an option, but it's generally not necessary in our region. Direct sowing works great and saves you some effort. However, if you're aiming for an extra-early start or want to get a jump on the season due to a late spring, starting indoors is a good strategy.

If you choose to start them indoors, sow seeds in late April through mid May, about three weeks before you intend to transplant them. Use seed trays filled with a good seed-starting mix and keep them warm and well-lit – a sunny windowsill or grow light works wonders. Be sure to water from the bottom to avoid damping off. Our variable spring weather can make indoor starting helpful, especially if we have a prolonged cool spell.

Transplant your sunflower seedlings outdoors in late May through mid June, once the risk of 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 room to grow. Keep an eye on the weather forecast around transplant time – a sudden hailstorm can wreak havoc on young plants. Wind protection is essential.

Direct sowing is the preferred method for sunflowers in the Great Plains. The seeds germinate quickly in our prairie soil once the soil warms up. Sow seeds mid May through mid June, ensuring the soil temperature is at least 60°F.

Prepare the soil by loosening it and adding compost or other organic matter. Plant the seeds 1-2 inches deep, spacing them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge. Sunflowers are easy to direct sow, and they'll take off quickly with our intense sunshine.

Sunflowers are relatively drought-tolerant once established, thanks to their deep taproot. However, consistent watering is crucial, especially during the initial growth stages. Knowing how to water in the Plains climate is important.

During the hot summer months, water deeply but infrequently. Aim for about 1 inch of water per week, depending on rainfall. Use the "finger test" – if the soil is dry 2 inches below the surface, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can encourage disease in our low-to-moderate humidity.

Keep an eye on your plants for signs of under or overwatering. Wilting leaves indicate a need for water, while yellowing leaves and soggy soil suggest overwatering. A layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is helpful in our variable rainfall conditions.

You can expect your first sunflower harvest in early August through mid September, about 80 days after planting. For harvesting seeds, wait until the back of the flower head turns brown and the seeds are plump and somewhat loose. Cut the entire head off the stalk, leaving several inches of stem.

To protect the seeds from birds, you can cover the heads with cheesecloth or paper bags as they mature. For cut flowers, harvest when the petals first open. As the first frost approaches in mid- September, you can cut the heads and hang them upside down in a dry, well-ventilated place to finish drying the seeds.

Here are the top three 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.
• What causes it: Birds are attracted to the ripening seeds.
• How to fix/prevent it: Cover the flower heads with netting, cheesecloth, or paper bags as the seeds mature. You can also use bird netting to protect larger areas.

Sunflower Moth

• What it looks like: Small caterpillars feeding on the flower head, often accompanied by webbing and seed damage.
• What causes it: Sunflower moths lay their eggs on the developing flower heads.
• How to fix/prevent it: Inspect plants regularly for caterpillars. Remove and destroy any infested heads. Insecticidal soap can be used preventatively, but timing is key.

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. Plant resistant varieties where available.

Great Plains Specific Challenges: Our region's hot heat and variable rainfall can stress sunflowers, making them more susceptible to pests and diseases. Wind protection is also important, as strong winds can damage the tall stalks.

Companion planting can help your sunflowers thrive in the Great Plains. Cucumbers and squash benefit from the shade provided by sunflowers, which helps retain moisture in our often-dry conditions. Green beans add nitrogen to the soil, benefiting the sunflowers. Corn can act as a windbreak, protecting the sunflowers from strong Plains winds. Lettuce can be planted around the base of sunflowers, as it appreciates the partial shade during the hottest part of the summer. Avoid planting potatoes near sunflowers, as they can compete for nutrients and attract similar pests.