How to Grow September Sun
Wikimedia Commons
September Sun
Helianthus annuus 'September Sun'
flowerSeptember Sun is a mid-sized sunflower variety known for its golden-yellow petals and dark center disk, typically reaching 4-5 feet tall. This cultivar is prized for its late-season blooming habit, producing cheerful flowers in fall when many gardens are fading. It's an excellent choice for cut flowers and adds vibrant color to autumn landscapes.
When should you plant September Sun in your zone?
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Example September Sun timeline · Pittsburgh, PA (Zone 6b)
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Plant September Sun
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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First September Sun blooms
Around Jun 26≈ 70 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact September Sun dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Zones 2-9; best in zones 5-8 for optimal fall blooming
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Seedling
2-3 weeksCotyledons and first true leaves emerge; plant is 2-4 inches tall with delicate, thin stems.
Keep soil consistently moist. Thin seedlings to proper spacing once they have 2-3 true leaves. Protect from slugs and cutworms with row covers if needed.
Vegetative Growth
4-6 weeksRapid stem elongation and leaf development; plant reaches 12-24 inches with multiple true leaves along the stem.
Water deeply but infrequently to encourage deep root growth. Stake or support plants in windy locations. Remove lower leaves if crowded to improve air circulation.
Budding
2-3 weeksTerminal bud forms at the top of the main stem; plant reaches full height (4-5 feet); multiple side buds may develop.
Ensure consistent moisture during bud development. Provide sturdy staking or support. Continue deadheading side buds if you want one large central flower.
Flowering
2-3 weeksLarge golden-yellow flower head opens, typically 4-6 inches in diameter, with brown disk florets in the center.
Flowers typically last 2-3 weeks. Water at the base during dry spells. Deadhead spent petals to encourage longevity. This variety's late-season timing means fall blooms.
Seed Maturation
3-4 weeksPetals drop; seed head dries and hardens; seeds fill the disk, turning gray or striped as they mature.
Allow head to dry on the plant if harvesting seeds for wildlife or replanting. Cover with netting if birds are an issue. Cut stems for drying as decorations.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Hand-pick beetles in early morning; use row covers on young plants; spinosad sprays if infestation is severe
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Strong water spray to dislodge; insecticidal soap; encourage beneficial insects like ladybugs
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Ensure good air circulation; water at soil level only; sulfur dust or neem oil if needed
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Increase humidity and water spray; neem oil; sulfur dust
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and
Netting over developing seed heads; reflective tape or scare devices
Uses
Sunflower seeds
CulinaryMature seeds are edible, nutritious, and rich in vitamin E, selenium, and healthy oils. They can be roasted and eaten as snacks or used in baking. [source]
Cut flowers and arrangements
HouseholdSeptember Sun's large, golden blooms are excellent for floral arrangements, garden displays, and seasonal decorating. The flowers last 1-2 weeks in water when cut in early morning. [source]
Dried decorations
HouseholdSeed heads dry beautifully and can be used in dried arrangements, wreaths, and fall decor for months without wilting. [source]
Pollinator and bird food
WildlifeFlowers attract bees and other pollinators; mature seed heads provide essential food for migrating birds and wildlife in autumn. [source]
Dye and natural color
CraftPetals and other parts can be used to create natural dyes for textiles and crafts, producing yellow and gold hues. [source]
Harvest Tips
Cut flowers for arrangements when petals are fully open but disk is still firm and mostly closed. Harvest in early morning for best vase life. For seed heads, wait until the back of the head turns brown and seeds are fully mature (late September through October), then cut and hang upside down to dry completely before harvesting seeds.
Fun Facts
- 🌱 September Sun was bred specifically to extend the sunflower season into fall, blooming when most other flowers have faded, making it ideal for late-season gardens.
- 🌱 Sunflowers exhibit heliotropism (sun-tracking) during their growth phase, with flower buds following the sun from east to west during the day; September Sun maintains this behavior even as a mature cultivar.
- 🌱 A single mature sunflower head can contain up to 2,000 seeds arranged in a mathematically perfect Fibonacci spiral pattern, a natural example of fractal geometry.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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