Helianthus giganteus L.
Asteraceae (Aster Family)
Synonym(s): Helianthus alienus, Helianthus borealis, Helianthus giganteus ssp. alienus, Helianthus giganteus var. subtuberosus, Helianthus nuttallii var. subtuberosus, Helianthus subtuberosus, Helianthus validus
USDA Symbol: hegi
As the name suggests, giant sunflower is a large, showy plant. A tall, rough, reddish stem bearing several to many light yellow flower heads. The branched, purplish stem grows to 12 ft. tall and bears terminal, yellow flowers.
Despite this plant's names, its flower heads are comparatively small; the common and species names actually refer to the plant's overall height.
From the Image Gallery
Plant CharacteristicsDuration: Perennial
Size Notes: Up to about 12 feet tall.
Fruit: Fruit is a cypsela (pl. cypselae). Though technically incorrect, the fruit is often referred to as an achene.
Bloom InformationBloom Color: Yellow
Bloom Time: Jul , Aug , Sep , Oct , Nov
DistributionUSA: CT , DC , DE , GA , IA , IL , IN , KY , MA , MD , ME , MI , MN , MS , NC , NJ , NY , OH , PA , SC , TN , VA , VT , WI , WV
Canada: MB , NS , ON , SK
Native Distribution: NY & Ont. to MN, s. to GA & KY; naturalized northeastward
Native Habitat: Moist places; marshes
Growing ConditionsLight Requirement: Sun
Soil Moisture: Moist , Wet
Soil Description: Moist soils
BenefitUse Wildlife: Seed heads attract birds.
Warning: The stems and leaves can cause skin irritation in humans. The plant can be fatal to animals if ingested. Humans should generally avoid ingesting plants that are toxic to animals.
Conspicuous Flowers: yes
Value to Beneficial InsectsSpecial Value to Native Bees
This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.
PropagationDescription: Excellent germination occurs with seeds that have been refrigerated over winter. Stem cuttings can be taken before flowering, but the easiest method of increase in to divide the clump in early spring.
Seed Collection: Nutlets usually mature 2-3 weeks after flowering. To beat finched to the seeds, secure a small bag around seeds heads after the flowers fade. Air-dry collected seed heads, separate nutlets from chaff, and store in sealed, refrigerated containers.
Commercially Avail: yes
Find Seed or Plants
Find seed sources for this species at the Native Seed Network.
National Wetland Indicator Status
From the National Organizations DirectoryAccording to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Native Seed Network - Corvallis, OR
Web ReferenceWebref 38 - Flora of North America (2019) Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Additional resourcesUSDA: Find Helianthus giganteus in USDA Plants
FNA: Find Helianthus giganteus in the Flora of North America (if available)
Google: Search Google for Helianthus giganteus
MetadataRecord Modified: 2022-12-28
Research By: TWC Staff