When to plant sunflowers

When to plant sunflowers by city

Sow sunflowers outdoors 1–4 weeks after your last frost, once the soil is at least 55°F. Here is what that means for 2027 in cities across the US, using each city’s average frost dates and the date its normal daily temperature reaches 55°F, so cool-spring places like Seattle wait for real warmth (NOAA 1991–2020). Pick the city with the climate most like yours, or enter your ZIP code above.

In frost-free parts of Florida, southern California and the Gulf Coast, timing is about heat instead: plant sunflowers in late winter or early spring and again in late summer.

Don’t go by the calendar alone. Sunflowers planted into cold soil sit still for weeks; wait until the soil 4 inches down is at least 55°F and nights stay above 50°F.

Sunflower spacing

How to grow sunflowers

Sunflowers are about as easy as gardening gets: big seeds, fast growth and dramatic flowers. Types range from 2-foot dwarfs to giants over 10 feet, plus branching and pollenless varieties for cutting. Kids love them, and so do bees and seed-eating birds.

Sun and soil

Full sun. Sunflowers tolerate poor and dry soil but grow best in well-drained soil with a pH around 6.0–7.5. Plant tall types on the north side of the garden so they do not shade other crops.

Planting

1. Direct-sow 1 inch deep, 1–4 weeks after the last frost, once soil is at least 55°F. They grow a taproot and do not like transplanting.
2. Sow seeds about 6 inches apart and thin to 18 inches apart in rows 30 inches apart.
3. For cut flowers all summer, sow a new batch every 2 weeks.

Care

• Water lightly but often until seedlings are up, then deeply about once a week.
• Go light on fertilizer; extra nitrogen gives tall, weak stems.
• Stake giant varieties or plant them where they are sheltered from wind.
• If you want the seeds, cover ripening heads with mesh or paper bags to keep birds and squirrels off.

Harvest

For cut flowers, cut in the morning as the petals start to open. For seed, wait until the back of the head turns from green to yellow-brown and the head droops. Cut it with about a foot of stem and hang it in a dry, airy place for a few weeks before rubbing the seeds out.

Common problems

• Birds and squirrels: They strip ripening heads. Cover heads once petals fall, or harvest a little early and finish drying indoors.
• Deer: Young plants are a favorite. Use fencing or repellents where deer are common.
• Powdery mildew and rust: Usually on older, lower leaves late in summer. Vigorous plants grow through it; space plants for airflow.
• Broken or leaning stalks: Wind topples tall types with heavy heads. Stake early or choose shorter varieties.

Varieties to try

• 'Mammoth' — giant, large striped seeds for eating
• 'Teddy Bear' — dwarf, fluffy double flowers
• 'ProCut' — pollenless single-stem cut flower
• 'Velvet Queen' — branching, deep red petals

Crop rotation

Sunflowers belong to the daisy family (Asteraceae). Few shared soil problems; fits anywhere in a rotation. Relatives that count as the same family for rotation: lettuce, red leaf lettuce, marigold, calendula, zinnia.

Sources

• Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020.
• Hardiness zones: 2023 USDA Plant Hardiness Zone Map, USDA-ARS and PRISM Climate Group, Oregon State University.
• Planting windows and spacing: Vegetable Planting Guide (GardenNotes #720), Colorado State University Extension, and other land-grant extension guides.
• Growing Sunflowers in the Home Garden — University of Georgia Extension
• Helianthus annuus (sunflower) — NC State Extension Plant Toolbox