L.
Identity
Unique IDELEMENT_GLOBAL.2.149677
Element CodePDAST4N0L0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderAsterales
FamilyAsteraceae
GenusHelianthus
Other Common NamesGiant Sunflower (EN) giant sunflower (EN) Hélianthe géant (FR) Swamp Sunflower (EN) Tuberous Sunflower (EN)
Concept ReferenceKartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-11-06
Change Date1988-04-30
Edition Date2025-11-06
Edition AuthorsSoteropoulos (2025)
Threat ImpactUnknown
Range Extent>2,500,000 square km (greater than 1,000,000 square miles)
Number of Occurrences> 300
Rank ReasonsHelianthus giganteus is a wide-ranging perennial forb found in usually wet, open sites, such as woodland edges, bog edges, moist thickets, ditches, and roadsides. It occurs in eastern North America, from Ontario and Manitoba, Canada south to South Carolina, Mississippi, and Iowa in the United States. It is introduced in New England and adjacent Canada. There are over 500 occurrences, which face threats from development, pasture, rights-of-way maintenance, succession and woody plant encroachment, hydrological alteration, invasive species, deer browsing, and other threats in some places. Little is known about trends, but with a large range extent and large number of occurrences, abundant habitat, and broad habitat preferences, this species is considered secure.
Range Extent CommentsHelianthus giganteus occurs in eastern North America, from Ontario and Manitoba, Canada south to South Carolina, Mississippi, and Iowa in the United States (FNA 2006, Weakley and the Southeastern Flora Team 2025). It is introduced in New England and adjacent Canada (Native Plant Trust 2025). Native range extent was estimated to be approximately 2,500,000 square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Occurrences CommentsBy applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are over 500 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Threat Impact CommentsAlthough threats are not widely documented, this species is threatened by development, pasture, rights-of-way maintenance, succession and woody plant encroachment, hydrological alteration, invasive species, deer browsing, and other threats in some places, though there is insufficient data, including anecdotal accounts, to understand scope and severity of threats for this species (NatureServe 2025). However, their overall impact is likely negligible given the species' broad range, large number of occurrences, tolerance of light disturbance, and affinity for typically abundant habitats.