Page authors: Don Knoke, David Giblin
Toxicodendron radicans var. rydbergii
poison-ivy, western poison-ivy

Distribution: Occurring east of the Cascades crest in Washington; distributed throughout much of North America, except Alaska, California, southeastern U.S. and northeastern Canada.

Habitat: General on the plains and foothills and into the lower mountains.

Flowers: April-July

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern


Somewhat pubescent shrub 0.5-2 m. tall.


Leaves trifoliate; leaflets broadly ovate, pointed, entire to shallowly lobed, 5-15 cm. long.


Inflorescence of congested, axillary panicles; flowers mostly imperfect, dioecious, 2-3 mm. long; calyx 5-parted, about half the length of the petals; petals 5; staminate flowers with 5 exerted stamens, the filaments attached to the rim of a fleshy, flat disk; ovary superior, style 1, stigmas 3.


Fruit drupe-like, glabrous, about 4 mm. long, white, with a greenish or yellowish cast.

Accepted Name:
Toxicodendron radicans (L.) Kuntze var. rydbergii (Small ex Rydb.) Erskine
Publication: Pl. Prince Edward Island 190. 1861.

Synonyms & Misapplications:
Rhus radicans L. var. rydbergii (Small ex Rydb.) Rehder
Rhus rydbergii (Small ex Rydb.) Greene
Rhus toxicodendron L. var. vulgaris Michx.
Toxicodendron radicans (L.) Kuntze ssp. radicans, misapplied
Toxicodendron rydbergii (Small ex Rydb.) Greene [IFBC]
Additional Resources:

PNW Herbaria: Specimen records of Toxicodendron radicans var. rydbergii in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Toxicodendron radicans var. rydbergii checklist entry.

OregonFlora: Toxicodendron radicans var. rydbergii information.

E-Flora BC: Toxicodendron radicans var. rydbergii atlas page.

CalPhotos: Toxicodendron radicans var. rydbergii photos.

USDA Plants: Toxicodendron radicans var. rydbergii information.

23 photographs:
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