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 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:
Bee host
Keystone species
Bee host
Keystone species
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 currently accept seeds for this plant
Fun Facts
As the name suggests, the Giant sunflower is a very tall plant and combined with its purplish stems and vibrant yellow blooms, it is sure to make a visibly impressive addition to a garden. It may not be appropriate for small spaces due to its rhizomes, which allow it to spread. Its seeds are eaten by many species of local birds as well as small rodents, and its leaves are eaten by other mammals such as deer.
The stems are so tall and robust that they have been used by beavers in building their dams and shelters.
The stems are so tall and robust that they have been used by beavers in building their dams and shelters.
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 - Écaille Cramoisie
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.