Toxicodendron rydbergii (Rydb.) Greene
Common Name: POISON-IVY
Synonym: Toxicodendron radicans
Coefficient of Conservatism: 3
Coefficient of Wetness: 0
Wetness Index: FAC
Physiognomy: Nt Shrub

Toxicodendron rydbergii A. A. Reznicek

Included in T. radicans in Michigan Flora.

Shores, dunes, and sunny slopes; in clearings and at forest borders; roadsides and railroads; usually in sandy, gravelly, or rocky soil. Occurring in southern Michigan only on sand near the shores of Lakes Michigan and Huron. The Kalamazoo Co. record is along a railway and may be an introduction.

This plant produces no aerial roots, so never climbs, and the leaflets are typically somewhat folded (often so when pressed); the petioles are glabrous or nearly so. Rare suspected hybrids between this and T. radicans have been identified from Gladwin, losco, Lapeer, Oceana, Oscoda, and St. Clair Cos., and likely occur elsewhere in the zone of overlap. This entity is distinct in the field, but more difficult to determine from herbarium specimens. 


Alcona County
Alger County
Allegan County
Alpena County
Antrim County
Arenac County
    Including Charity Island
Baraga County
Bay County
Benzie County
Charlevoix County
    Including Beaver Island
Cheboygan County
Chippewa County
Crawford County
Delta County
Dickinson County
Emmet County
Gladwin County
Gogebic County
Grand Traverse County
Houghton County
Huron County
Iosco County
Iron County
Kalamazoo County
Kalkaska 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
Menominee County
Missaukee County
Montmorency County
Muskegon County
Oceana County
Ogemaw County
Ontonagon County
Osceola County
Oscoda County
Otsego County
Ottawa County
Presque Isle County
Roscommon County
Sanilac County
Schoolcraft County
St. Clair County
Tuscola County
Wexford County


MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. November 29, 2022.