Sunflower in Zone 7B — Texas

Sunflowers aren’t just pretty faces; they're a rewarding addition to any Texas garden. Imagine harvesting your own sunflower seeds for snacking, or brightening up your home with vibrant, homegrown cut flowers. Plus, they're surprisingly easy to grow, even with our Texas heat.

Our unpredictable weather can be a challenge, but with a little planning, you can enjoy sunflowers throughout our long, 255-day growing season. We can usually dodge the worst of the heat by planting smart, and the long season means you have plenty of time to get it right.

While sunflowers thrive when direct-sown, starting them indoors can give you a head start, especially if you're aiming for early blooms. Start your seeds indoors mid-February through early March, about three weeks before you plan to transplant. This is especially useful when our spring is early, which is not uncommon here.

Use seed trays filled with a good quality potting mix, and keep them warm and well-lit – a sunny windowsill or grow light works great. Water from the bottom to prevent damping off; just set the tray in a shallow dish of water until the soil surface is moist.

Transplant your sunflower seedlings outdoors mid-March through mid-April, after they've developed a few sets of true leaves. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Texas sun and wind.

Choose a sunny spot with well-draining soil, and space your seedlings 18-24 inches apart. Keep an eye on the forecast around transplant time; we can sometimes get a late freeze that could damage young plants.

Direct sowing is the preferred method for sunflowers, as they resent root disturbance. Sow seeds early March through mid-August, giving you plenty of opportunities for successive plantings. This is great for ensuring a continuous supply of blooms.

Prepare your soil by loosening it and amending with compost. Plant seeds about 1 inch deep, spacing them 18-24 inches apart. Keep the soil consistently moist until germination, which usually takes about a week. Sunflowers sprout quickly and grow fast, so you'll see results in no time.

Sunflowers are moderately drought-tolerant once established, thanks to their deep taproots. However, regular watering is essential, especially during those brutal summer months. Water deeply but infrequently, encouraging those roots to dig down.

During the spring and fall, when temperatures are milder and rainfall is more likely (but still unpredictable!), water about once a week, providing about 1 inch of water. In the heat of summer, you may need to water two or three times a week, especially if we're in a dry spell. Use the "finger test" – if the top 2 inches of soil feel dry, it's time to water. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases, especially with our variable humidity.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of your sunflowers can help retain moisture and suppress weeds, but be careful not to pile it against the stem.

You can expect your first sunflower harvest late May through mid-November, about 80 days after planting. For sunflower seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose. You can cut the entire head off and hang it upside down in a dry, well-ventilated place to dry completely before harvesting the seeds.

For cut flowers, harvest when the petals first open. Cut the stem at an angle and place it in water immediately. As first frost approaches in mid- November, harvest any remaining heads, even if they're not fully mature. You can still dry the seeds indoors.

Here are some common problems you might encounter with sunflowers in Texas:

Birds Eating Seeds

• What it looks like: Missing seeds from the flower head, often with signs of pecking.
• What causes it: Birds love sunflower seeds! It’s especially bad when seeds are ripening.
• How to fix/prevent it: Cover the flower 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, brown moths flying around the sunflowers. Larvae (caterpillars) feeding on seeds, causing damage and webbing.
• What causes it: Sunflower moths are attracted to sunflowers, especially during bloom. They lay eggs on the flower heads, and the larvae burrow into the seeds.
• How to fix/prevent it: Inspect flower heads regularly for signs of moth activity. Remove and destroy any infested heads. You can also use 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: Downy mildew is caused by 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 around the plants. Water at the base, never overhead. Copper-based fungicides can be used for prevention.

Texas-Specific Challenges: Our hot-to-extreme heat can stress sunflowers, making them more susceptible to pests and diseases. Variable humidity can also contribute to fungal problems like downy mildew. Unpredictable rainfall can make it difficult to maintain consistent soil moisture, so be sure to monitor your plants closely and adjust your watering accordingly.

Sunflowers make great companions for many plants in your Texas garden. Cucumbers and squash benefit from the shade provided by sunflowers during the hottest part of the day. Green beans can use sunflower stalks as a natural trellis. Corn and sunflowers are a classic pairing, as they both thrive in similar conditions. Lettuce can also benefit from the partial shade provided by sunflowers.

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