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Helianthus giganteus

Helianthus giganteus L.

Giant Sunflower

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

USDA Native Status: L48 (N), CAN (N)

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

4 photo(s) available in the Image Gallery

Plant Characteristics

Duration: Perennial
Habit: Herb
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 Information

Bloom Color: Yellow
Bloom Time: Jul , Aug , Sep

Distribution

USA: 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 Conditions

Light Requirement: Sun
Soil Moisture: Moist , Wet
Soil Description: Moist soils

Benefit

Use 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 Insects

Special Value to Native Bees

This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.

Propagation

Description: 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

Region:	AGCP	AK	AW	CB	EMP	GP	HI	MW	NCNE	WMVE
Status:	FACW				FACW	FAC		FACW	FACW

This information is derived from the U.S. Army Corps of Engineers National Wetland Plant List, Version 3.1 (Lichvar, R.W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-49: 1-241). Click here for map of regions.

From the National Organizations Directory

According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:

Native Seed Network - Corvallis, OR

Web Reference

Webref 38 - Flora of North America (2019) Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.

Additional resources

USDA: Find Helianthus giganteus in USDA Plants
FNA: Find Helianthus giganteus in the Flora of North America (if available)
Google: Search Google for Helianthus giganteus

Metadata

Record Modified: 2022-12-28
Research By: TWC Staff

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