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Montana Field Guide

Montana Field Guides

Western Poison-ivy - Toxicodendron rydbergii
Other Names:  Rhus radicans, Toxicodendron radicans var. rydbergii, Rhus toxicodendron

Native Species

Global Rank: G5
State Rank: S5

Agency Status
MNPS Threat Rank:
C-value: 4

External Links

General Description
Rhizomatous subshrub, shrub, or (rarely) vine. Stems erect, 10–50 cm, pubescent, branched and bearing leaves above. Herbage glabrous, sparsely pubescent on veins, allergenic. Leaves trifoliate, long-petiolate; leaflets ovate, remotely serrate to entire, 2–12 cm long, shiny above; lateral leaflets asymmetrical. Inflorescence an axillary, few-branched panicle. Flowers white; petals 2–3 mm long, dark-veined. Drupes crowded, globose, greenish-yellow, 4–6 mm long (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Montana Range


Range Comments
Much of temperate North America (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 107

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Streambanks, woodlands, open forest; plains, valleys (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Fritzen, D.E. 1995. Ecology and behavior of Mule Deer on the Rosebud Coal Mine, Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 143 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
    • Seipel, T.F. 2006. Plant species diversity in the sagebrush steppe of Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 87 p.
    • Steerey, W. F. 1979. Distribution, range use and population characteristics of Mule Deer associated with the Schafer Creek winter range, Bridger Mountains, Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 119 p.
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Citation for data on this website:
Western Poison-ivy — Toxicodendron rydbergii.  Montana Field Guide.  .  Retrieved on , from