E-Flora BC: Electronic Atlas of the Flora of British Columbia

Toxicodendron rydbergii (Small ex Rydb.) Greene
poison ivy (western poison ivy)
Anacardiaceae (Sumac family)

Introduction to Vascular Plants

© Gordon Neish  Email the photographer   (Photo ID #23653)

E-Flora BC Static Map
Distribution of Toxicodendron rydbergii
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Western poison ivy is a native species that is found across the US and Canada (excluding a cluster of states in the southeastern US, Alaska, California, Nunavut, and the Northwest Territories) (USDA 2010). Disjunct populations are reported from mountaintops of the central Appalachians (McMurray 1988). In British Columbia, it may be encountered in south-central regions and particularly in the Okanagan Valley. Throughout its range, it occurs on a variety of habitats ranging from riverbanks and lakeshores at low elevations to subalpine sites. In BC, it is most often noticed along river and lake shorelines (e.g. Vaseaux Lake) where it is moderately abundant. It is a distinctive, usually erect, rhizomatous small shrub up to 2 m in height. It most often occurs as a subshrub (McMurray 1988). Branching is simple. It has three shiny, pointed leaves and numerous monecious flowers occur in dense clusters in the leaf axils. Berries are white, sometimes greenish-yellow. Leaves often appear slightly drooping and exude milky sap when broken or cut. Western poison ivy can cause dermatological reactions when touched, resulting in an itchy rash, and should not be handled.

Species Information

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Deciduous slender shrub, decumbent to erect, ivylike, up to 2 m tall, somewhat hairy, exuding milky juice when cut.
Leaflets 3, abruptly sharp-pointed or long-pointed, broadly egg-shaped, entire or shallowly crenate to lobed, 5-15 cm long.
Inflorescence of crowded axillary panicles; flowers 2-3 mm long.
Berrylike drupes, 4 mm long, white to greenish-yellow, glabrous.
The slightly volatile oils of this plant cause an allergic reaction for some people.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Dry to mesic slopes in the montane zone; infrequent in SC and SE BC, rare in SW BC; E to PQ, NB and NS and S to MX.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Toxicodendron rydbergii

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 205 470 1181
Slope Gradient (%) 0 24 77
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
20 190 320
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 3 7
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(50), ICH(1), IDF(21), PP(18)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Rhus radicans
Rhus radicans var. rydbergii (Small ex Rydb.) Rehder
Rhus radicans var. vulgaris (Michx.) DC.
Rhus rydbergii
Rhus toxicodendron var. vulgaris Michx.
Toxicodendron desertorum Lunell
Toxicodendron radicans var. rydbergii (Small ex Rydb.) Erskine

Taxonomic and Nomenclatural Links

Additional Photo Sources

Species References

McMurray, Nancy E. 1988. Toxicodendron rydbergii. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

General References