Vernonia gigantea(Walter) Trel.

giant ironweed

WFO wfo-0000000462 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Vernonia gigantea, photographed by Lauren Gillett
fig. a Lauren Gillett, CC BY 4.0 / 2022-05-18 / obs. 198723125
Vernonia gigantea, photographed by vrschmalhofer
fig. b vrschmalhofer, CC BY 4.0 / obs. 161960056
Vernonia gigantea, photographed by Kathy Richardson
fig. c Kathy Richardson, CC BY 4.0 / obs. 157253542
Vernonia gigantea, photographed by Yann Kemper
fig. d Yann Kemper, CC0 1.0 / obs. 156781131
Vernonia gigantea, photographed by Gregory Bennett
fig. e Gregory Bennett, CC0 1.0 / obs. 152579713
Vernonia gigantea, photographed by Heather DeGaetano
fig. f Heather DeGaetano, CC0 1.0 / obs. 152209466
Vernonia gigantea, photographed by the swamp ass
fig. g the swamp ass, CC BY 4.0 / obs. 152092091
Vernonia gigantea, photographed by Melissa McMasters
fig. h Melissa McMasters, CC BY 4.0 / obs. 162329299

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 25 botanical countries

Regions where Vernonia gigantea is native: Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Nebraska, New York, North Carolina, Ohio, Oklahoma, Ontario, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia AlabamaArkansasFloridaGeorgiaIllinoisIndianaKansasKentuckyLouisianaMarylandMichiganMississippiMissouriNebraskaNew YorkNorth CarolinaOhioOklahomaOntarioPennsylvaniaSouth CarolinaTennesseeTexasVirginiaWest Virginia
Native distribution of Vernonia gigantea, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows.
RegionTDWG codeContinent
Alabama ALA NORTHERN AMERICA
Arkansas ARK
Florida FLA
Georgia GEO
Illinois ILL
Indiana INI
Kansas KAN
Kentucky KTY
Louisiana LOU
Maryland MRY
Michigan MIC
Mississippi MSI
Missouri MSO
Nebraska NEB
New York NWY
North Carolina NCA
Ohio OHI
Oklahoma OKL
Ontario ONT
Pennsylvania PEN
South Carolina SCA
Tennessee TEN
Texas TEX
Virginia VRG
West Virginia WVA

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Flowering 497 in flower of 549 examined

Peak flowering in Aug. Each bar is the share of Vernonia gigantea observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 497 of 549 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Also published as 21 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Cacalia gigantea (Walter) Kuntze
  • Cacalia gigantea var. gigantea
  • Chrysocoma gigantea Walter
  • Chrysocoma gigantea (Walt.) Kuntze
  • Chrysocoma praealta Desf.
  • Vernonia altissima Nutt.
  • Vernonia altissima var. altissima
  • Vernonia altissima var. brevipappa Gleason
  • Vernonia altissima var. laxa Gleason
  • Vernonia altissima var. lilacina Clute
  • Vernonia altissima var. taeniotricha S.F.Blake
  • Vernonia gigantea subsp. ovalifolia (Torr. & A.Gray) Urbatsch
  • Vernonia gigantea subsp. pubescens E.Morris
  • Vernonia gigantea var. gigantea
  • Vernonia gigantea var. ovalifolia (Torr. & A.Gray) D.B.Ward
  • Vernonia maxima Small
  • Vernonia maxima subsp. maxima
  • Vernonia maxima var. maxima
  • Vernonia oligantha Greene
  • Vernonia ovalifolia Torr. & A.Gray
  • Vernonia ovalifolia var. ovalifolia

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.