Rydberg’s poison-ivy (Toxicodendron rydbergii, Leafl. Bot. Observ. Crit. 1: 117 (1905))

Family: Anacardiaceae

Author: (Small ex Rydb.) Greene

Bibliography: Leafl. Bot. Observ. Crit. 1: 117 (1905)

Year: 1905

Status: accepted

Rank: species

Genus: Toxicodendron

Vegetable: False

Observations: N. America to Mexico (Sonora, Chihuahua)

Description

Rydberg’s poison-ivy, scientifically known as Toxicodendron rydbergii, is a fascinating and notable member of the plant family Anacardiaceae. Described in the Leaflets of Botanical Observations and Criticisms in 1905 by renowned botanist Edward L. Greene, with contributions from John Kunkel Small and Per Axel Rydberg, this species has caught the curiosity and meticulous attention of scientists for over a century.

This deciduous shrub is extensively distributed across North America and can extend its reach as far south as Sonora and Chihuahua in Mexico. Its widespread presence throughout various regions underscores its adaptability and resilience in diverse environmental conditions. Rydberg’s poison-ivy thrives in a range of habitats, from wooded areas to open spaces, often found alongside trails and roadsides where it can be an unassuming yet treacherous part of the flora.

One of the distinctive features of Toxicodendron rydbergii is its trifoliate leaf structure. Each leaflet typically has smooth or slightly toothed edges and can vary in shape, often appearing glossy green during the growing season and transforming into brilliant hues of red, orange, and yellow in autumn. These vibrant seasonal shifts not only highlight its aesthetic appeal but also serve as a cautionary reminder of its potent irritants.

The plant is infamous for its production of urushiol, an oily compound that can cause severe allergic reactions in humans. Contact with any part of the plant—whether it be the leaves, stems, or roots—can result in an itchy, blistering rash. Hence, it is crucial for hikers, gardeners, and outdoor enthusiasts to recognize and steer clear of this toxic beauty.

Despite its hazardous nature, Rydberg’s poison-ivy holds a nuanced position within the ecosystem. It provides habitat and food for various wildlife species. Birds, in particular, are known to consume the white drupes produced by the plant, aiding in seed dispersal and, inadvertently, contributing to the plant’s expansive range.

The legacy of Toxicodendron rydbergii, from its early documentation by pioneering botanists to its enduring presence across vast terrains, marks it as a significant specimen within its genus. Awareness and knowledge about Rydberg’s poison-ivy are indispensable, not only for its cautionary aspects but also for its consistent role in biodiversity and ecological dynamics.

Common Names

Eng: poison ivy, rydberg’s poison-ivy, western poison ivy
En: Rydberg’s poison-ivy, Western poison ivy, Western poison-ivy, W. Poison ivy, Poison ivy

Synonyms

• Toxicodendron pumilum (Greene)
• Rhus toxicodendron var. rydbergii ((Small ex Rydb.) Garrett)
• Rhus toxicodendron var. vulgaris (Michx.)
• Rhus radicans subsp. rydbergii ((Small ex Rydb.) McNeill)
• Rhus radicans var. vulgaris ((Michx.) DC.)
• Rhus radicans var. rydbergii ((Small ex Rydb.) Rehder)
• Toxicodendron punctatum (Greene)
• Rhus rydbergii (Small ex Rydb.)
• Toxicodendron desertorum (Lunell)
• Toxicodendron radicans subsp. rydbergii ((Small ex Rydb.) Á.Löve & D.Löve)
• Toxicodendron radicans var. rydbergii ((Small ex Rydb.) Erskine)
• Toxicodendron rufescens (Greene)
• Toxicodendron macrocarpum (Greene)
• Toxicodendron fothergilloides (Lunell)
• Toxicodendron longipes (Greene)

Distribution

• Alberta (native)
• Arizona (native)
• British Columbia (native)
• Connecticut (native)
• Idaho (native)
• Illinois (native)
• Indiana (native)
• Iowa (native)
• Kansas (native)
• Maine (native)
• Manitoba (native)
• Maryland (native)
• Masachusettes (native)
• Mexico Northeast (native)
• Mexico Northwest (native)
• Michigan (native)
• Minnesota (native)
• Montana (native)
• Nebraska (native)
• Nevada (native)
• New Brunswick (native)
• New Hampshire (native)
• New Jersey (native)
• New Mexico (native)
• New York (native)
• North Carolina (native)
• North Dakota (native)
• Nova Scotia (native)
• Ohio (native)
• Oklahoma (native)
• Ontario (native)
• Oregon (native)
• Pennsylvania (native)
• Prince Edward I. (native)
• Québec (native)
• Rhode I. (native)
• Saskatchewan (native)
• South Dakota (native)
• Texas (native)
• Utah (native)
• Vermont (native)
• Virginia (native)
• Washington (native)
• West Virginia (native)
• Wisconsin (native)
• Wyoming (native)
• Yukon (native)

Additional Images

Fruit

Taken Nov 24, 2022 by Rachel Lambes (cc-by-sa)

Taken Nov 3, 2022 by Jeanne Dion-D (cc-by-sa)

Taken Dec 28, 2013 by EOL − Robert L Curtis (cc-by-nc-sa)

Taken Jan 8, 2022 by Richard Wideman (cc-by-sa)

Taken Feb 7, 2022 by G T (cc-by-sa)

Flower

Taken Jun 1, 2021 by Heidi Aupers (cc-by-sa)

Leaf

Taken Jul 8, 2015 by EOL − Liana May (cc-by-nc-sa)

Taken Sep 4, 2020 by Bryan Challis (cc-by-sa)

Taken Sep 25, 2020 by Kel Ess (cc-by-sa)

Taken May 30, 2021 by Lindsay Disney (cc-by-sa)

Taken May 25, 2019 by sarah jaber (cc-by-sa)

Habit

Taken Jun 18, 2015 by EOL − Liana May (cc-by-nc-sa)

Taken May 23, 2015 by EOL − Jesse Rorabaugh (cc-by)

Taken Jun 9, 2014 by EOL − Robert L Curtis (cc-by-nc-sa)

Taken Jun 9, 2014 by EOL − Robert L Curtis (cc-by-nc-sa)

Taken Oct 12, 2014 by EOL − Charlie Hohn (cc-by-nc)

Sources

• WFO (No URL)
• IPNI (No URL)
• GBIF (https://www.gbif.org/species/3190615)
• POWO (http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:255789-2)
• PlantNet (https://identify.plantnet.org/species/the-plant-list/Toxicodendron rydbergii (Small ex Rydb.) Greene)

Specifications

Growth habit>: Shrub, Forb/herb, Vine

Growth