| 词条 | Helianthus debilis | ||
| 释义 |
|image = Tournesol de la Plage (5954050557).jpg |status = G5 |status_system = TNC |genus = Helianthus |species = debilis |authority = Nutt. |synonyms_ref = [1] |synonyms = *Helianthus cucumerifolius Torr. & A.Gray, syn of subsp. cucumerifolius
}}{{Commons category|Helianthus debilis}}Helianthus debilis is a species of sunflower known by the common names cucumberleaf sunflower, beach sunflower, weak sunflower,[1] and East Coast dune sunflower.[2] It is native to the United States, where it can be found along the Atlantic and Gulf Coasts.[3] It is known elsewhere as an introduced species, such as South Africa, Australia, Taiwan, Slovakia, and Cuba.[4] This species may be an annual or perennial herb.[3] It is usually perennial but it may last only one season in climates where freezes occur.[5] It can reach 2 meters tall. The stem grows from a taproot and may grow erect or decumbent.[3] It can also spread along the ground, becoming a dense groundcover.[5] The leaves are usually alternately arranged, 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[3] or 21[6] ray florets, each up to 2.3 centimeters long. They are usually yellow in the wild, but cultivars have been bred to bear whitish,[6] reddish, or orange florets.[5] The center of the head is filled with many red, yellowish,[3] or purplish[6] disc florets. The fruit, a cypsela, is roughly 2 or 3 millimeters long.[3] There are several subspecies. At one point there were eight.[7] Five are currently recognized.[8][3]
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.[5][6] The plant attracts butterflies and birds feed on the fruits.[5] 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',[6] 'Flora Sun',[21]'Dazzler', 'Excelsior', and 'Orion'.[5] GalleryDune Sunflowers growing in Miami Beach sand dunes (South Beach) References1. ^{{GRIN | accessdate = 21 January 2018}} {{Taxonbar|from=Q12212016}}2. ^Wunderlin, R. P. and B. F. Hansen. 2008. Helianthus debilis. Atlas of Florida Vascular Plants. Institute for Systematic Botany, University of South Florida, Tampa. 3. ^1 2 3 4 5 6 Helianthus debilis. Flora of North America. 4. ^1 {{GRIN | Helianthus debilis subsp. cucumerifolius | 104288 | accessdate = 21 January 2018}} 5. ^1 2 3 4 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. 6. ^1 2 3 4 Christman, S. Helianthus debilis. Floridata.com. 1999. Updated 2003. 7. ^Wain, R. P. (1983). [https://www.jstor.org/discover/10.2307/2408835?uid=3739560&uid=2129&uid=2&uid=70&uid=4&uid=3739256&sid=21102294499807 Genetic differentiation during speciation in the Helianthus debilis complex.] Evolution 37(6) 1119-27. 8. ^1 The Plant List, Helianthus debilis Nutt. 9. ^Helianthus debilis ssp. cucumerifolius. Flora of North America. 10. ^{{GRIN | Helianthus debilis subsp. debilis | 300254 | accessdate = 21 January 2018}} 11. ^Helianthus debilis ssp. debilis. Flora of North America. 12. ^{{GRIN | Helianthus debilis subsp. silvestris | 104290 | accessdate = 21 January 2018}} 13. ^Helianthus debilis ssp. silvestris. Flora of North America. 14. ^{{GRIN | Helianthus debilis subsp. tardiflorus | 104291 | accessdate = 21 January 2018}} 15. ^Helianthus debilis ssp. tardiflorus. Flora of North America. 16. ^Helianthus debilis ssp. tardiflorus. NatureServe. 17. ^{{GRIN | Helianthus debilis subsp. vestitus | 104292 | accessdate = 21 January 2018}} 18. ^1 Helianthus debilis ssp. vestitus. NatureServe. 19. ^Helianthus debilis ssp. vestitus. Flora of North America. 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. ^1 Maura, C. and S. Sanders. Helianthus debilis ssp. debilis Plant Fact Sheet. USDA NRCS Brooksville Plant Materials Center. 2002. 3 : Helianthus|Flora of the United States|Plants described in 1841 |
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