Helenium amarum

{{Short description|Species of flowering plant}}

{{Speciesbox

|image = Helenium amarum1.jpg

| status = G5

| status_system = TNC

| status_ref = {{cite web |title=NatureServe Explorer 2.0 |url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.145025/Helenium_amarum |website=explorer.natureserve.org}}

|genus = Helenium

|species = amarum

|authority = (Raf.) H.Rock

|synonyms_ref = {{ThePlantList}}{{Tropicos|50132443|Gaillardia amara}}

|synonyms = *Gaillardia amara Raf.

• Galardia amara Raf.
• Helenium badium (A.Gray ex S.Watson) Greene

}}

Helenium amarum is a species of annual herb in the daisy family known by the common names yellowdicks, yellow sneezeweed, fiveleaf sneezeweed, and bitter sneezeweed. It is native to much of the south-central United States (Texas, Oklahoma, Louisiana, Arkansas, New Mexico) and northern Mexico (Chihuahua, Coahuila), and it is present elsewhere in North America, Australia, and the West Indies as an introduced species.{{BONAP|ref |genus=Helenium |species=amarum}}Turner, B. L. 2013. The comps of Mexico. A systematic account of the family Asteraceae (chapter 11: tribe Helenieae). Phytologia Memoirs 16: 1–100.[http://www.tropicos.org/Name/2700849?tab=specimens Tropicos, specimen listing for Helenium amarum (Raf.) H. Rock ][https://www.daf.qld.gov.au/plants/weeds-pest-animals-ants/weeds/a-z-listing-of-weeds/photo-guide-to-weeds/bitter-weed Queensland Government, Department of Agriculture and Fisheries, Bitter weed (Helenium amarum)]

Helenium amarum is a multibranched bushy erect plant reaching 20 to 70 centimeters (8-28 inches) in height and thickly foliated in narrow to threadlike leaves. The tops of stem branches hold inflorescences of many daisy-like flower heads. Each head has a rounded center of sometimes as many as 250 golden yellow disc florets and a fringe of 8-10 usually lighter yellow ray florets which are reflexed away from the center. The fruit is a tiny achene about a millimeter long. This herb is weedy in some areas.{{eFloras|1 |tribe=Heliantheae |first=Mark W. |last=Bierner}}

The plant is somewhat toxic to mammalsIvie, G. W., et al. (1975). Toxicity and milk bittering properties of tenulin, the major sesquiterpene lactone constituent of Helenium amarum (bitter sneezeweed). J Agric Food Chem 23:5 845-9. and insectsArnason, J. T., et al. (1987). Mode of action of the sesquiterpene lactone, tenulin, from Helenium amarum against herbivorous insects. J Nat Prod 50:4 690-5. due to the presence of the lactone tenulin.

; Varieties

• Helenium amarum var. amarum - United States
• Helenium amarum var. badium Waterf. - Oklahoma, Texas, Chihuahua, Coahuila