Helianthus angustifolius

{{Short description|Species of sunflower}}

{{cs1 config |name-list-style=vanc}}

{{use dmy dates|date=July 2024}}

{{Speciesbox

|image = Helianthus angustifolius 2.jpg

|status = G5

|status_system = TNC

|status_ref =

|genus = Helianthus

|species = angustifolius

|authority = L.

|synonyms_ref = {{cite web |url=http://www.theplantlist.org/tpl1.1/record/gcc-23433 |website=The Plant List |title=Helianthus angustifolius L. |access-date=4 July 2015 |archive-date=26 July 2020 |archive-url=https://web.archive.org/web/20200726083612/http://www.theplantlist.org/tpl1.1/record/gcc-23433 |url-status=live }}

|synonyms = *Coreopsis angustifolia L. 1753 not Ait. 1789

• Discomela angustifolius Raf.

}}

Helianthus angustifolius is a species of sunflower known by the common name narrowleaf sunflower or swamp sunflower. It is native to the south-central and eastern United States, found in all the coastal states from Texas to Long Island, and inland as far as Missouri.{{GRIN | accessdate = 19 January 2018}}{{cite web |url=http://bonap.net/MapGallery/County/Helianthus%20angustifolius.png |website=Biota of North America Program |year=2014 |title=Helianthus angustifolius county distribution map |access-date=4 July 2015 |archive-date=10 May 2015 |archive-url=https://web.archive.org/web/20150510144101/http://bonap.net/MapGallery/County/Helianthus%20angustifolius.png |url-status=live }} It is typically found in the coastal plain habitat (both the Atlantic and Gulf), particularly in wet areas. Although, in general, this species prefers low, moist ground, it is tolerant of conditions varying from bogs and swamps near sea level to relatively dry, well drained, gravelly clay.{{Cite thesis |last=Martin |first=William C. Jr.|year=1958 |title=The Taxonomy of Helianthus angustifolius and Related Species |url=https://www.proquest.com/docview/301906123 |access-date=2024-07-30 |degree=PhD |publisher=Indiana University |id={{ProQuest|301906123}} |language=en}} It is not particularly drought resistant.{{Cite journal |last1=Chapman |first1=Douglas S. |last2=Auge |first2=Robert M. |date=March 1994 |title=Physiological-Mechanisms of Drought Resistance in 4 Native Ornamental Perennials |url=https://journals.ashs.org/jashs/view/journals/jashs/119/2/article-p299.xml |journal=Journal of the American Society for Horticultural Science |volume=119 |issue=2 |pages=299–306 |doi=10.21273/JASHS.119.2.299 |access-date=2024-07-30 |archive-date=20 May 2024 |archive-url=https://web.archive.org/web/20240520024654/https://journals.ashs.org/jashs/view/journals/jashs/119/2/article-p299.xml |url-status=live |doi-access=free }}

Helianthus angustifolius is often cultivated for its bright, showy yellow flowers. Leaves are long and narrow, up to {{convert|15|cm}} long. It is a perennial herb sometimes as much as {{convert|150|cm}} tall. One plant can produce 3-16 flower heads, each with 10-20 ray florets surrounding at least 75 disc florets.{{cite web |url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242416628 |website=Flora of North America |title=Helianthus angustifolius Linnaeus, 1753 |access-date=4 July 2015 |archive-date=30 April 2015 |archive-url=https://web.archive.org/web/20150430070457/http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242416628 |url-status=live }}