Sunflower in Zone 8B — Florida

Sunflowers are a fantastic addition to any Florida garden, offering beauty, edible seeds, and even cut flowers. Their height and sunny disposition bring a smile, and harvesting your own seeds is incredibly rewarding. Plus, they attract pollinators, which is always a win.

Our Florida gardening calendar is different, and while the summer is the slow season for many crops, sunflowers can be timed to thrive. With our long, 303-day growing season, you can successfully grow sunflowers if you plan for our humidity and occasional heavy rains.

While sunflowers do best when direct sown, you *can* start them indoors if you want a head start, especially for an earlier flower display. Start your seeds indoors from late January through mid February, about three weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them warm and well-lit.

Bottom watering is key to avoid damping off. Remember, our spring here is reversed compared to other parts of the country, so getting a jump start indoors can give you a beautiful display before the heat really kicks in.

Transplant your sunflower seedlings outdoors from late February through late March. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space them 18-24 inches apart in a sunny spot. Keep an eye on the weather forecast; a late cold snap could still happen, so be ready to cover them if needed.

Direct sowing is the easiest and most recommended way to grow sunflowers in Florida. Sow seeds from mid February through mid September. Sunflowers grow quickly, so even sowing later in the season can still yield a good harvest.

Prepare the soil by loosening it and adding compost. Plant the seeds about 1 inch deep and space them 18-24 inches apart. Water well after planting and keep the soil consistently moist until they germinate.

Sunflowers need moderate watering, but they're also drought-tolerant once established thanks to their deep taproots. During our drier spring months, check the soil moisture regularly. Stick your finger about 2 inches deep; if it feels dry, it's time to water.

In general, give your sunflowers about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the leaves, which can encourage fungal diseases in our humid climate. During our wet-summer months, you might not need to water at all, but keep an eye out for signs of overwatering like yellowing leaves.

If the leaves are drooping even when the soil is moist, you might be overwatering. Adding a layer of mulch around the base of the plants can help retain moisture during drier periods and prevent soil from splashing onto the leaves during heavy rains.

You can expect your first sunflower harvest from early May through mid December, depending on when you planted. For seeds, wait until the back of the flower head turns brown and the seeds are plump and slightly loose. This usually takes about 80 days from planting.

To harvest the seeds, 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, harvest them when the petals first open. As our first frost approaches around mid- December, harvest any remaining mature heads.

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

Birds Eating Seeds

• What it looks like: Sunflower heads with missing or damaged seeds. You might also see birds actively feeding on the seeds.
• What causes it: Birds love sunflower seeds! It's a natural food source for them.
• How to fix/prevent it: Cover the flower heads with netting or burlap bags once the seeds start to mature. You can also try using bird deterrents like shiny tape or decoys.

Sunflower Moth

• What it looks like: Small caterpillars inside the sunflower heads, feeding on the developing seeds. You might also see webbing and frass (caterpillar droppings).
• What causes it: Sunflower moths lay their eggs on the developing flower heads. The larvae hatch and burrow into the head to feed on the seeds.
• How to fix/prevent it: Inspect flower heads regularly for signs of infestation. Remove any infested heads and dispose of them properly. 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.

Florida Specific Challenges: The combination of hot heat, very-high humidity, and our wet-summer rainfall makes sunflowers particularly susceptible to fungal diseases like downy mildew. Be sure to provide good air circulation, avoid overhead watering, and consider planting resistant varieties to minimize these problems. Also, our sandy soil means you will need to amend it well with compost to retain moisture and nutrients.

Good companion plants for sunflowers include cucumbers, squash, and green beans. Cucumbers and squash provide ground cover, which helps to suppress weeds and retain moisture. Green beans fix nitrogen in the soil, which benefits the sunflowers. Corn also makes a good companion, as the tall stalks can help support the sunflowers in windy conditions. Lettuce is a good choice to plant around sunflowers as well, as the sunflowers can offer some shade during the hottest part of the day.

Avoid planting potatoes near sunflowers. Potatoes can attract nematodes, which can damage the sunflower roots.