Helianthus decapetalus L.
Common Name: THIN-LEAVED SUNFLOWER, PALE SUNFLOWER
Coefficient of Conservatism: 5
Coefficient of Wetness: 3
Wetness Index: FACU
Physiognomy: Nt P-Forb

Widespread in beech, maple, and red oak forests, especially at borders and openings; also river banks and floodplain forests.

The leaves tend to be thinner in texture than the thick ones of H. strumosus, but that is a comparative and qualitative character unsuited for a key. The petioles in both these species may be as short as 7 mm, but in H. decapetalus they can be as long as 35 mm; in H. strumosus they do not, in our material, exceed 13 (or very rarely 15) mm.

Specimens of Heliopsis helianthoides are occasionally misidentified as this species, for there is some similarity in leaf shape and general pubescence characters. In Heliopsis the outer phyllaries are rounded or only somewhat acute, and the ray flowers are fertile, whereas in Helianthus decapetalus the phyllaries are prolonged-acuminate and (as in other species of Helianthus) the ray flowers are sterile.

Locations

Allegan County
Berrien County
Branch County
Calhoun County
Cass County
Genesee County
Gratiot County
Hillsdale County
Ingham County
Ionia County
Jackson County
Kalamazoo County
Kent County
Lapeer County
Lenawee County
Livingston County
Macomb County
Monroe County
Muskegon County
Newaygo County
Oakland County
Oceana County
Saginaw County
Shiawassee County
St. Clair County
St. Joseph County
Van Buren County
Washtenaw County
Wayne County

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 18, 2017. http://www.michiganflora.net/species.aspx?id=347.