Sunflower in Zone 5B — Great Plains

Sunflowers are a fantastic addition to any Great Plains garden. Their towering height and bright blooms bring beauty, and the seeds are delicious roasted or used for birdseed. Plus, they're relatively easy to grow and thrive in our intense sunshine, adding a touch of cheer to the prairie landscape.

Our region is known for extreme weather, including wind, drought, and the occasional hail storm. But don't let that deter you! With careful timing and a few smart strategies, you can successfully grow sunflowers during our roughly 178-day growing season.

While sunflowers are best direct-sown, you *can* start them indoors in late March through mid April, about three weeks before transplanting. This might be helpful if you want a head start, especially in the northern part of our zone where the growing season is shorter, or if you're aiming for an earlier bloom.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist by bottom watering – set the tray in a shallow dish of water and let the soil soak it up from the bottom. This helps prevent damping-off. Place the trays in a warm spot with plenty of light, either a sunny window or under grow lights. Keep in mind that our springs can be variable, so be prepared to adjust your setup if we get an unexpected cold snap.

Transplant your sunflower seedlings outdoors in late April through late May, after the risk 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 and increase the time and sun exposure each day.

Choose a sunny spot with well-drained soil, spacing the plants 18-24 inches apart. Our spring weather can be unpredictable, so keep an eye on the forecast and be ready to cover the young plants if a late frost threatens. Wind protection is essential, especially for young transplants.

Direct sowing is the preferred method for sunflowers in the Great Plains. The best time to sow seeds is mid April through mid July. Sunflowers are easy to direct sow and grow quickly.

Prepare the soil by loosening it and removing any weeds. Sow seeds about 1 inch deep and 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge, which should take about a week. Soil temperature needs to be at least 60°F for successful germination.

Sunflowers are moderately drought-tolerant once established, thanks to their deep taproot. However, consistent watering is crucial, especially during the initial growth stages and during extended dry periods. The key is to water deeply but infrequently.

During the spring, when rainfall is more frequent, you may only need to supplement with watering once a week, if at all. As the hot summer months approach, increase watering to about 1-2 inches per week, depending on rainfall. Use the finger test: stick your finger about 2 inches into the soil near the base of the plant. 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 moderate humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, indicated by yellowing leaves and a mushy stem base. A layer of mulch around the base of the plants will help retain moisture and suppress weeds during our hot summers.

You can expect your first sunflower harvest from early July through mid October, about 80 days after planting. If you're growing sunflowers for seeds, wait until the back of the head turns brown and the seeds are plump and slightly loose.

To harvest the seeds, cut the entire head off the stalk, leaving about a foot of stem attached. Hang the head upside down in a well-ventilated place to dry completely. Once dry, you can easily rub the seeds out of the head. If you're growing sunflowers for cut flowers, cut the stems when the petals first open.

As the first frost approaches in mid- October, harvest any remaining sunflower heads, even if they're not fully mature. You can bring them indoors to dry and ripen.

Here are the top 3 common problems with sunflowers in the Great Plains:

Birds Eating Seeds

• What it looks like: Sunflower heads with missing seeds or damage, often with birds seen actively feeding on the plants.
• What causes it: Birds are attracted to the readily available and nutritious sunflower seeds.
• How to fix/prevent it: Cover the sunflower heads with netting or burlap bags as the seeds mature. You can also try using bird deterrents like reflective tape or decoys.

Sunflower Moth

• What it looks like: Small caterpillars inside the sunflower heads, feeding on the developing seeds. You may also see webbing and frass (caterpillar droppings) on the heads.
• What causes it: Sunflower moths lay their eggs on the developing flower heads. The larvae hatch and burrow into the head to feed.
• How to fix/prevent it: Inspect your sunflower heads regularly for signs of infestation. Remove any affected heads and dispose of them. 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: Our hot summers and variable rainfall can stress sunflowers, making them more susceptible to pests and diseases. Wind protection is also crucial to prevent the tall plants from toppling over. Monitor your plants closely and take action quickly to address any problems that arise.

Good companions for sunflowers in the Great Plains include cucumbers and squash. They help suppress weeds and provide ground cover, keeping the soil cool and moist during our hot summers. Green beans add nitrogen to the soil, benefiting the sunflowers. Corn provides wind protection, especially for young plants. Lettuce can be grown in the shade of the sunflowers during the hottest part of the day.

Avoid planting potatoes near sunflowers. Potatoes are heavy feeders and can compete with sunflowers for nutrients in our prairie soil.