Helianthus decapetalus, known by the common names thinleaf sunflower,[ Biota of North America Program 2014 county distribution map][ USDA, NRCS. 2014. The PLANTS Database (http://plants.usda.gov). National Plant Data Team, Greensboro, NC 27401-4901 USA.] It produces yellow Pseudanthium in late summer or early fall.
The name decapetalus means "with ten petals", referring to the 8-12 ray florets on the flower heads, resembling petals.
Description
The smooth slender stem of
H. decapetalus is 60 to 200 cm (2 to 7 ft) tall and branched near the top. The ovate or lanceolate leaves are borne on 2- to 5-cm-long petioles and have serrated edges. They are 7 to 21 cm long and 4 to 10 cm wide. It has three to 10 flowerheads; each flowerhead is composed of 21 to 50
, and eight to 12
, which are 2.0 to 2.5 cm long. The bracts are typically 11 to 16 mm long, surpassing the flower disk by at least half their length. The fruit are 3.5- to 5.0-mm-long cypselae with a pappus of two scales.
[Britton, Nathaniel Lord & Brown, Addison (1913). An Illustrated Flora of the Northern United States, Canada and the British Possessions: From Newfoundland to the Parallel of the Southern Boundary of Virginia, and from the Atlantic Ocean Westward to the 102d Meridian, Volume 3., p. 484. Charles Scribner's Sons, New York.][ 'eFloras (2008). Published on the Internet (http://www.efloras.org). Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.]
Distribution and habitat
In
Virginia, it grows in habitats such as floodplain forests and riverbanks.
[ Virginia Botanical Associates. (2014). Digital Atlas of the Virginia Flora (http://www.vaplantatlas.org). c/o Virginia Botanical Associates, Blacksburg.] Its native habitats include woodland and forest edges.
The presence of this species is dependent on appropriate
habitat, and it may be eliminated from an area by development, changes in land use, or competition with
invasive species.
Ecology
The flowers attract many kinds of insects, including bees and butterflies, some of which, such as the
Vanessa cardui and the
Chlosyne nycteis, use the plant as a larval host. The seeds provide a source of food for birds.
[ Copyright © 2002-2012 Dr. John Hilty. Illinois Wildflowers (http://www.illinoiswildflowers.info)] eat the leaves and stems and use the stems in the construction of their lodges.
