Source: US Fish and Wildlife Service
Plant Names
Helianthus giganteus
Giant Sunflower
Hélianthe géant
Synonyms
swamp sunflower
tall sunflower
soleil géant
Plant Characteristics
Bloom Colour: Yellow
Bloom Period: Jul - Sep
Max Height: 8.0 feet
Max Width: 4.0 feet (spreads by rhizome)
Light Condition:
More than 6 hours of direct sun a day
More than 2 or 3 hours but less than 6 hours of direct sun a day
Soil conditions:
Tolerates medium soil condition
More than 6 hours of direct sun a day
More than 2 or 3 hours but less than 6 hours of direct sun a day
Tolerates medium soil condition
Lifespan:
Perennial
plants that will that come back year after year
Gardener Experience:
Does not spread uncontrollably
Spreads by rhizome
Easy to germinate
Self-seeding
Does not spread uncontrollably
Spreads by rhizome
Easy to germinate
Self-seeding
Landscape Uses:
No landscape information available.
Ecological Benefits:
Supports pollinators
Bee host
Supports pollinators
Bee host
Tolerates:
Tolerates limestone conditions
Tolerates juglone conditions
Tolerates limestone conditions
Tolerates juglone conditions
Special Features and Considerations:
Seed and plant distribution status
No seeds available for this plant.
We are not accepting seeds for this plant at the moment.
Plant Location
Distribution according to VASCAN
Ephemeral
Native
Introduced
Excluded
Extirpated
Doubtful
Absent
Canadensis
Thrives in Ecozones
- Atlantic Maritime
- Boreal Plains
- Boreal Shield
- Mixed Wood Plains
Ecological Benefits
Butterflies Supported by Helianthus giganteus
- Euplexia benesimilis (American Angle Shades)
- Phragmatobia fuliginosa (Ruby Tiger)
Specialized Bees Supported by Helianthus giganteus
- Andrena aliciae
- Andrena chromotricha
- Andrena helianthi
- Complexe Colletes americanus
- Dianthidium simile
- Megachile inimica
- Megachile pugnata
- Melissodes agilis
- Melissodes denticulatus
- Melissodes illatus
- Melissodes trinodis
- Perdita pallidipennis
Complementary Plants
- Lobelia spicata
Pale-spike Lobelia
Lobélie à épi - Solidago rigida
Stiff Goldenrod
Verge d'or rigide - Sorghastrum nutans
Yellow False-sorghum
Faux-sorgho penché - Symphyotrichum novae-angliae
New England Aster
Aster de Nouvelle-Angleterre - Teucrium canadense
Canada Germander
Germandrée du Canada
Substitute For Non-Native Plants
- Leucanthemum (Shasta Daisy)
- Gerbera (Gerbera Daisy)
- NA (Non-native False Sunflower)
Sowing Information
Download Seed Envelope Labels (PDF)
- Sowing depth: Sow just below surface
- Sow by March
- Stratification duration: 30 days
- Self-seeding
Harvesting and Seed Sharing
- Harvest start month: September
- Harvesting indicator:
- Seeds easily fall off when you gently pull them off
- Harvesting:
- Shake seed head in paper bag
- Seed viability test:
- No test needed before donating
- Packaging measure: 1 rounded 1/4 teaspoon
- Seed storage:
- Air dry in paper bag or open container, for a few days until crisp
- Shake seeds to move them once in a while to prevent molding
- Cultivar: Yes, do not donate unless you know source, and there are no known cultivars in your garden or at proximity
- Remove non-seed material
- No harvesting video available at this time.
Toxicity Notes
Inadequate information on toxicity found.