Ambrosia psilostachya DC.
Coefficient of Conservatism: *
Coefficient of Wetness: 0
Wetness Index: FAC
Physiognomy: Ad P-Forb

Usually considered native west of Michigan; not collected in the state until 1902 (Emmet and Kent Cos.) and 1903 (St. Clair Co.); it was already on Isle Royale by 1910.

The fruits lack thorn-like protuberances below the beak, or at least some of them are poorly developed and blunt. The longer, denser hairs on the leaves give the plant a decidedly gray-green aspect, quite noticeable in the field, contrasting with the darker green aspect of A. artemisiifolia.

Hybrids with A. artemisiifolia are relatively widespread in Michigan, and have been named A. ×intergradiens W. H. Wagner. Also perennial, the hybrid often closely resembles A. psilostachya, but tends to be intermediate in several respects, especially intermediate pubescence on the leaves. In the field, the hybrid usually exists in a clone near the parent species, making it more readily distinguished.


Alcona County
Alger County
Allegan County
Alpena County
Antrim County
Baraga County
Benzie County
Berrien County
Charlevoix County
    Including Beaver Island
Cheboygan County
Chippewa County
    Including Drummond Island
Clare County
Crawford County
Delta County
Dickinson County
Emmet County
Gogebic County
Grand Traverse County
Houghton County
Jackson County
Kalamazoo County
Kalkaska County
Kent County
Keweenaw County
    Including Isle Royale
Lake County
Leelanau County
    Including Fox Islands
    Including Manitou Islands
Luce County
Mackinac County
    Including Bois Blanc, Mackinac, Round Islands
Manistee County
Marquette County
Mason County
Mecosta County
Menominee County
Montcalm County
Montmorency County
Muskegon County
Newaygo County
Otsego County
Ottawa County
Presque Isle County
Schoolcraft County
St. Clair County
Van Buren County
Wexford County


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 16, 2022.