Thinleaf Sunflower, Ten-petal Sunflower, Forest Sunflower, Pale Sunflower - Helianthus decapetalus
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Helianthus decapetalus - Thinleaf Sunflower, Ten-petal Sunflower, Forest Sunflower, Pale Sunflower. Helianthus decapetalus is an occasionally branching plant from 2 to 5 feet tall, with multiple flower heads on long stalks. It is a relatively leafy sunflower, with opposite leaves on the lower part of the plant and alternate leaves on the upper part of the plant. This is one of the sunflowers that may have green or reddish stems. The stems are smooth, occasionally glaucous, in the lower part, and may have short hairs in the upper area, usually so in the inflorescence. It blooms in late summer and well into fall.
Found in:
AL, CT, DC, DE, GA, IA, IL, IN, KS, KY, LA, MA, MD, ME, MI, MO, MS, NC, NH, NJ, NY, OH, OK, PA, RI, SC, TN, VA, VT, WI, WV
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Distribution of Helianthus decapetalus in the United States and Canada:
Map courtesy of The Biota of North America Program.
Map color key
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| | Site: Grundy County, TN Date: 2011-September-17 | Photographer: Gerald C. Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro | | The 8 to 12 ray florets are up to around an inch long. The disk may be up to around 3/4" across, with around 40 florets. The species epithet and one of the common names - Ten-petal Sunflower - indicate that 10 is a pretty common number of ray florets, although this plant has only 8. | | 
| | Site: Grundy County, TN Date: 2011-September-17 | Photographer: Gerald C Williamson
Nikon D7000 | | The phyllaries are longer than the disk is wide, are narrow and sharply pointed, and have hair edges. The blossom stem is pubescent. | | Click on the photo for a larger image
| | Site: Grundy County, TN Date: 2011-September-17 | Photographer: Gerald C Williamson
Nikon D7000
Tamron SP 90MM f/2.8 AF Macro | | The inflorescence may have only a single blossom, but more normally will have several. | | Click on the photo for a larger image
| | Site: Grundy County, TN Date: 2011-September-17 | Photographer: Gerald C Williamson
Nikon D7000 | | One to several branches of Helianthus decapetalus is terminated by one or more blossoms. | | Click on the photo for a larger image
| | Site: Grundy County, TN Date: 2011-September-17 | Photographer: Gerald C Williamson
Nikon D7000 | | The upper surface of the leaf is dark green and rough-feeling, and the lighter green lower surface may have a few scattered hairs. The margins of the larger leaves have sharply pointed teeth, and are on a short petiole that forms from the tapering base of the leaf. This tapering leaf base give the appearance of a winged petiole. | | Click on the photo for a larger image
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References used for identification and information:
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