Sunflower in Zone 4A — Great Plains

Sunflowers are a classic for a reason, and they earn their place in any Great Plains garden. Their cheerful faces brighten the landscape, and you can harvest the seeds for snacks or leave them for the birds. Plus, they're surprisingly drought-tolerant once established, which is a big win in our variable climate.

We know our region throws curveballs with extreme temperature swings and the occasional hail, but don't let that scare you off. With a little planning and attention to timing, you can absolutely grow beautiful sunflowers within our 138-day growing season.

Starting sunflowers indoors is possible, but honestly, they do so well direct-sown that it's usually not worth the effort. If you're in the northern part of our region with a shorter season, or if you just want a head start, you can start seeds indoors from mid-April through early May, about 3 weeks before you plan to transplant.

Use seed trays with good drainage and a well-draining potting mix. Keep them warm and provide plenty of light – a sunny windowsill or grow lights work well. I like to bottom water my seedlings to encourage strong root growth and prevent damping off, which can be a problem with our variable spring weather.

If you started your sunflowers indoors, you can transplant them outdoors from mid-May through mid-June, once the risk of frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a sunny spot with well-drained soil and space your plants 18-24 inches apart. Keep an eye on the forecast, as we can still get some late-season cool snaps or even hail that can damage young transplants.

Direct sowing is the easiest and most reliable way to grow sunflowers in the Great Plains. Sow seeds from early May through late June, anytime after the soil has warmed up to at least 60°F. Sunflowers germinate best in warm soil.

Prepare your soil by loosening it and adding some compost. Plant seeds about 1 inch deep and space them 18-24 inches apart. Keep the soil consistently moist until the seedlings emerge, which should take about a week. Sunflowers are easy to direct sow and grow quickly, so you'll be enjoying their sunny blooms in no time.

Sunflowers are surprisingly drought-tolerant once they establish their deep taproot, which is great for our region's variable rainfall. However, they still need regular watering, especially when they're young.

During the first few weeks after planting, water deeply and regularly to encourage strong root growth. After that, you can reduce watering frequency, but still aim for about 1 inch of water per week, either from rainfall or irrigation. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. In our low-to-moderate humidity, it's usually best to water at the base of the plant to avoid fungal diseases.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, so make sure your soil is well-draining. A layer of mulch around the base of the plants can help retain moisture and suppress weeds, which is especially helpful during our hot summers.

You can expect your first sunflower harvest from late July through late September, depending on when you planted. For sunflower seeds, wait until the back of the flower head turns brown and the seeds are plump and easy to remove.

To harvest the seeds, you can cut the entire flower head off the stalk and hang it upside down in a dry, well-ventilated place until the seeds are completely dry. For cut flowers, cut the stems when the petals first open.

As our first frost approaches in late September, you can either harvest any remaining seeds or leave the flower heads on the stalks for the birds to enjoy throughout the winter.

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

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 nutritious sunflower seeds, especially as other food sources become scarce.
• How to fix/prevent it: Cover the flower heads with netting or burlap bags to protect the seeds. You can also plant extra sunflowers specifically for the birds.

Sunflower Moth

• What it looks like: Small, brown moths flying around the sunflower heads. Larvae (caterpillars) feeding on the seeds, leaving behind webbing and frass (insect poop).
• What causes it: Sunflower moths lay their eggs on the flower heads, and the larvae hatch and feed on the developing seeds.
• How to fix/prevent it: Inspect flower heads regularly for signs of infestation. Remove and destroy any infested heads. You can also use 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 heat, low-to-moderate humidity, and variable rainfall can stress sunflowers, making them more susceptible to pests and diseases. Providing adequate water and ensuring good air circulation can help prevent these problems. The wind can also be a challenge, so consider planting sunflowers in a sheltered location or providing support to prevent them from toppling over.

Sunflowers make great companions for several plants in the Great Plains garden. Cucumbers and squash benefit from the sunflowers providing shade during our hot summers, which prevents sunscald. Green beans can use the sunflower stalks as a natural trellis. Corn also grows well alongside sunflowers, as they both have similar nutrient needs. Lettuce appreciates the afternoon shade provided by the tall sunflowers, which prevents bolting in the heat. Avoid planting potatoes near sunflowers, as they can compete for nutrients and attract similar pests.