Helianthus debilis

Short description: Species of sunflower

Helianthus debilis

Conservation status

Secure (NatureServe)

Scientific classification
Kingdom:  | Plantae
Clade:  | Tracheophytes
Clade:  | Angiosperms
Clade:  | Eudicots
Clade:  | Asterids
Order:  | Asterales
Family:  | Asteraceae
Genus:  | Helianthus
Species:  |

H. debilis

Binomial name
Helianthus debilis

Nutt.

Synonyms[1]

* Helianthus cucumerifolius Torr. & A.Gray, syn of subsp. cucumerifolius
* Helianthus vestitus E.Watson, syn of subsp. vestitus

Helianthus debilis is a species of sunflower known by the common names cucumberleaf sunflower, beach sunflower, weak sunflower,[2] and East Coast dune sunflower.[3] It is native to the United States, where it can be found along the Atlantic and Gulf Coasts.[4] It is known elsewhere as an introduced species, such as South Africa , Australia , Taiwan, Slovakia, and Cuba.[5]

This species may be an annual or perennial herb.[4] It is usually perennial but it may last only one season in climates where freezes occur.[6] It can reach a height of 2 meters. The stem grows from a taproot and may grow erect or decumbent.[4] It can also spread along the ground, becoming a dense groundcover.[6] The leaves are usually arranged alternately and are variable in shape and size. The largest are up to 14 centimeters long by 13 wide. The showy inflorescence is a single flower head or an array of two or three heads. There are up to 30 lance-shaped phyllaries each up to 1.7 centimeters long. There are up to 20[4] or 21[7] ray florets, each up to 2.3 centimeters long. They are usually yellow in the wild, but cultivars have been bred to bear whitish,[7] reddish, or orange florets.[6] The center of the head is filled with many red, yellowish,[4] or purplish[7] disc florets. The fruit, a cypsela, is roughly 2 or 3 millimeters long.[4]

There are several subspecies. At one point there were eight.[8] Five are currently recognized.[1][4]

* Helianthus debilis subsp. cucumerifolius \- cucumberleaf sunflower. The subspecies with the widest distribution.[5][9]
* Helianthus debilis subsp. debilis \- beach sunflower. Endemic to Florida.[10][11]
* Helianthus debilis subsp. silvestris \- forest sunflower. Endemic to Texas .[12][13]
* Helianthus debilis subsp. tardiflorus \- slow-flowering sunflower. Mississippi to Florida.[14][15] Limited to rare, specialized coastal habitat.[16]
* Helianthus debilis subsp. vestitus \- clothed sunflower,[17] hairy beach sunflower.[18] Endemic to Florida.[19] Imperiled; known from about 22 occurrences.[18]

This species grows in several types of coastal habitat, sometimes directly on the beach. It tolerates a moderately saline environment, but not an excessive amount of salt spray or inundation.[20] It is highly drought-tolerant and it will grow in low-nutrient and poor soils, such as alkaline and acidic soils and sand.[6][7] The plant attracts butterflies and birds feed on the fruits.[6]

This plant is used as a garden flower. It is also good for landscaping, especially in poor, dry soils. It is planted on beaches, where it forms a sand-binding groundcover that prevents erosion and stabilizes dunes.[21] It requires supplemental watering only rarely, if ever. It may get "ratty-looking" after the showy flowers have withered.[20] Available cultivars include 'Italian White',[7] 'Flora Sun',[21]'Dazzler', 'Excelsior', and 'Orion'.[6]

## Gallery

Dune Sunflowers growing in Miami Beach sand dunes (South Beach)

* Sea Grapes and Dune Sunflowers

* Dune Sunflower Closeup

## References

1. ↑ 1.0 1.1 The Plant List, Helianthus debilis Nutt.
2. ↑ {{citation | mode = cs1 | title = Helianthus debilis | work = Germplasm Resources Information Network (GRIN) | url = | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
3. ↑ Wunderlin, R. P. and B. F. Hansen. 2008. Helianthus debilis. Atlas of Florida Vascular Plants. Institute for Systematic Botany, University of South Florida, Tampa.
4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Helianthus debilis. Flora of North America.
5. ↑ 5.0 5.1 {{citation | mode = cs1 | title = Helianthus debilis subsp. cucumerifolius | work = Germplasm Resources Information Network (GRIN) | url = https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?104288 | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Gilman, E. F. and S. Park-Brown. Helianthus debilis Beach Sunflower. Environmental Horticulture, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. 1999. Revised 2007.
7. ↑ 7.0 7.1 7.2 7.3 7.4 Christman, S. Helianthus debilis. Floridata.com. 1999. Updated 2003.
8. ↑ Wain, R. P. (1983). Genetic differentiation during speciation in the Helianthus debilis complex. Evolution 37(6) 1119-27.
9. ↑ Helianthus debilis ssp. cucumerifolius. Flora of North America.
10. ↑ {{citation | mode = cs1 | title = Helianthus debilis subsp. debilis | work = Germplasm Resources Information Network (GRIN) | url = https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?300254 | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
11. ↑ Helianthus debilis ssp. debilis. Flora of North America.
12. ↑ {{citation | mode = cs1 | title = Helianthus debilis subsp. silvestris | work = Germplasm Resources Information Network (GRIN) | url = https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?104290 | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
13. ↑ Helianthus debilis ssp. silvestris. Flora of North America.
14. ↑ {{citation | mode = cs1 | title = Helianthus debilis subsp. tardiflorus | work = Germplasm Resources Information Network (GRIN) | url = https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?104291 | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
15. ↑ Helianthus debilis ssp. tardiflorus. Flora of North America.
16. ↑ Helianthus debilis ssp. tardiflorus. NatureServe.
17. ↑ {{citation | mode = cs1 | title = Helianthus debilis subsp. vestitus | work = Germplasm Resources Information Network (GRIN) | url = https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?104292 | publisher = [[Organization:Agricultural Research ServAgricultural Research Service (ARS), United States Department of Agriculture (USDA) | access-date = 21 January 2018 }}
18. ↑ 18.0 18.1 Helianthus debilis ssp. vestitus. NatureServe.
19. ↑ Helianthus debilis ssp. vestitus. Flora of North America.
20. ↑ 20.0 20.1 Gann, G. D., et al. 2005-2013. East Coast dune sunflower Helianthus debilis. Natives For Your Neighborhood. The Institute for Regional Conservation. Delray Beach, Florida, USA.
21. ↑ 21.0 21.1 Maura, C. and S. Sanders. Helianthus debilis ssp. debilis Plant Fact Sheet. USDA NRCS Brooksville Plant Materials Center. 2002.

Wikidata ☰ Q12212016 entry

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