Helenium quadridentatum

{{Short description|Species of flowering plant}}

{{Speciesbox

| image = Actes de la société d'histoire naturelle de Paris - tome premier, premiere partie (1792) (16585970589).jpg

| genus = Helenium

| species = quadridentatum

| authority = Labill. 1792

| synonyms_ref = [http://www.theplantlist.org/tpl1.1/record/gcc-143983 The Plant List, Helenium quadridentatum Labill. ]

| synonyms = *Heleniastrum quadridentatum (Labill.) Kuntze

• Tetrodus quadridentatus (Labill.) Cass. ex Less.

}}

Helenium quadridentatum is a North American plant in the family Asteraceae, commonly known as longdisk sneezeweed. It is found in the southeastern and south-central United States (Alabama, Mississippi, Louisiana, Texas, Oklahoma)[http://bonap.net/MapGallery/County/Helenium%20quadridentatum.png Biota of North America Program 2014 county distribution map] as well as Mexico (from Tamaulipas to Yucatán), Cuba, Guatemala, and Belize.Balick, M. J., M. H. Nee & D.E. Atha. 2000. Checklist of the vascular plants of Belize. Memoirs of The New York Botanical Garden 85: i–ix, 1–246Turner, B. L. 2013. The comps of Mexico. A systematic account of the family Asteraceae (chapter 11: tribe Helenieae). Phytologia Memoirs 16: 1–100

Helenium quadridentatum is an annual herb up to {{convert|100|cm|in|round=0.5|abbr=on}} tall, with small wings running down the sides of the stems. Leaves are sometimes broadly elliptical, other times very narrow and grass-like. One plant generally produces up to 50 flower heads, in a branching array. Each head has an egg-shaped or conical disc containing can have 500 or more minuscule disc flowers each {{convert|1.1|–|1.8|mm|in|abbr=on}} across, each yellow toward the bottom but yellow-brown toward the tip. There are also 10-15 yellow ray flowers.[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=250066858 Flora of North America, Helenium quadridentatum Labillardière, 1792. Longdisk sneezeweed ][https://www.biodiversitylibrary.org/page/45494803#page/56/mode/1up Labillardière, Jacques Julien Houtou de. 1792. Actes de la Société d'Histoire Naturelle de Paris 1: pages 22-23] diagnosis in Latin, description + commentary + figure captions in French[https://www.biodiversitylibrary.org/page/45494803#page/173/mode/1up Labillardière, Jacques Julien Houtou de. 1792. Actes de la Société d'Histoire Naturelle de Paris 1: plate IV (4)] full-page line drawing of Helenium quadridentatum