Helianthus giganteus L.
Common Name: TALL SUNFLOWER
Coefficient of Conservatism: 5
Coefficient of Wetness: -3
Wetness Index: FACW
Physiognomy: Nt P-Forb

This is one species surely native in Michigan, where it favors moist sites: wet prairies, fens, sedge meadows, tamarack swamps; river banks and floodplain forests; borders of upland forests and wet depressions; marshes, and ditches.

Helianthus giganteus is an immensely variable species, The leaves are rarely opposite or whorled, and may be densely gland-dotted beneath. The roots may be thickened or tuberous.

This species hybridizes with H. grosseserratus, producing H. ×luxurians E. Watson; it is said to differ from H. giganteus in having petioles 2–3 cm long and stems green, yellow, or light red (rather than dark red or purple), although one or both of these characters is lacking in many of the specimens examined. It differs from H. grosseserratus in having stems pubescent (rather than glabrous) and phyllaries usually pubescent and with marginal cilia (not glabrous or with short scattered hairs). The hybrid with H. divaricatus is mentioned under that species.

Locations

Allegan County
Arenac County
Barry County
Bay County
Berrien County
Calhoun County
Cass County
Clinton County
Delta County
Dickinson County
Genesee County
Gratiot County
Hillsdale County
Huron County
Ingham County
Jackson County
Kalamazoo County
Kent County
Keweenaw County
Lapeer County
Leelanau County
Lenawee County
Livingston County
Macomb County
Mason County
Mecosta County
Menominee County
Midland County
Monroe County
Montcalm County
Muskegon County
Newaygo County
Oakland County
Ontonagon County
Ottawa County
St. Clair County
Tuscola 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 13, 2017. http://www.michiganflora.net/species.aspx?id=349.