Helianthus debilis

Helianthus debilis
Conservation status
Secure  (NatureServe)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Asterales
Family:	Asteraceae
Genus:	Helianthus
Species:	H. debilis
Binomial name
Helianthus debilis Nutt.

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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.

• H. d. ssp. cucumerifolius - cucumberleaf sunflower. The subspecies with the widest distribution.^[4][8]
• H. d. ssp. debilis - beach sunflower. Endemic to Florida.^[9][10]
• H. d. ssp. silvestris - forest sunflower. Endemic to Texas.^[11][12]
• H. d. ssp. tardiflorus - slow-flowering sunflower. Mississippi to Florida.^[13][14] Limited to rare, specialized coastal habitat.^[15]
• H. d. ssp. vestitus - clothed sunflower,^[16] hairy beach sunflower.^[17] Endemic to Florida.^[18] Imperiled; known from about 22 occurrences.^[17]

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.^[19] 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.^[20] It requires supplemental watering only rarely, if ever. It may get "ratty-looking" after the showy flowers have withered.^[19] Available cultivars include 'Italian White',^[6] 'Flora Sun',^[20]'Dazzler', 'Excelsior', and 'Orion'.^[5]

References