Ambrosia artemisiifolia L.
Coefficient of Conservatism: 0
Coefficient of Wetness: 3
Wetness Index: FACU
Physiognomy: Nt A-Forb

Ambrosia artemisiifolia A. A. Reznicek

Although weedy in habit, considered native and known from Michigan as early as 1838 (Cass Co.). By the 1880’s, documented from Detroit, Wayne Co. to Keweenaw Co. Favored habitats include roadsides, railroads, fields, farmyards, cultivated ground, logged areas, and other disturbed sites; also in oak savanna, on stream banks and even floodplains, rocky ground.

Plants can be quite large (even to 1 m tall) and bushy, whereas in A. psilostachya they are usually little if at all branched. The fruits have a ring of well-developed thorn-like protuberances below the base of the beak.

Besides the hybrid with A. psilostachya mentioned under that species, a much less common hybrid with A. trifida is known, A. ×helenae Rouleau. This has been recognized thus far in Michigan only in Cheboygan, Hillsdale, and Washtenaw Cos.


Alcona County
Alger County
Allegan County
Alpena County
Antrim County
Arenac County
Baraga County
Barry County
Bay County
Benzie County
Berrien County
Branch County
Calhoun County
Cass County
Charlevoix County
Cheboygan County
Chippewa County
    Including Drummond Island
Clare County
Clinton County
Crawford County
Delta County
Dickinson County
Emmet County
Gogebic County
Grand Traverse County
Gratiot County
Hillsdale County
Houghton County
Ingham County
Iosco County
Iron County
Isabella County
Jackson County
Kalamazoo County
Kalkaska County
Kent County
Keweenaw County
Lake County
Lapeer County
Leelanau County
    Including Fox Islands
    Including Manitou Islands
Lenawee County
Livingston County
Mackinac County
    Including Bois Blanc, Mackinac, Round Islands
Macomb County
Manistee County
Marquette County
Mason County
Mecosta County
Menominee County
Midland County
Missaukee County
Monroe County
Montcalm County
Montmorency County
Muskegon County
Newaygo County
Oakland County
Oceana County
Ogemaw County
Ontonagon County
Osceola County
Oscoda County
Otsego County
Ottawa County
Presque Isle County
Roscommon County
Saginaw County
Sanilac County
Schoolcraft County
Shiawassee County
St. Clair County
St. Joseph County
Tuscola County
Van Buren County
Washtenaw County
Wayne County
Wexford County


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 24, 2022.