western poison ivy

(Toxicodendron rydbergii)

Conservation Status
western poison ivy
 
  IUCN Red List

not listed

     
  NatureServe

N5 - Secure

SNR - Unranked

     
  Minnesota

not listed

     
           
           
           
           
           
           
Weed Status

Specially Regulated Plant

In 2010, the Minnesota Department of Agriculture added eastern poison ivy and western poison ivy to the Specially Regulated Plant list.

Must be eradicated or controlled for public safety along rights-of-ways, trails, public accesses, business properties open to the public or on parts of lands where public access for business or commerce is granted. Must also be eradicated or controlled along property borders when requested by adjoining landowners.

Poison ivy is beneficial to many wildlife species, but exposure to it causes severe skin irritation to humans and sometimes to livestock. Smoke from burning it can cause serious respiratory problems.

             
Wetland Indicator Status
       
  Great Plains

FACU - Facultative upland

       
  Midwest

FAC - Facultative

       
  Northcentral & Northeast

FAC - Facultative

       
             
 
Description
 
 

Western poison ivy is an erect, perennial shrub that rises on a single stem from a usually underground rhizome. It often forms colonies. The plant is usually a ground cover, sometimes a shrub, rarely a vine. If it is a vine it climbs weakly, and will not climb trees.

Stems are woody, erect, usually unbranched, and lack aerial roots.

Leaves are alternate and are borne near the end of the stem usually on leaf stalks. The leaf stalks are hairless and ½ to 10 long. The base of the leaf stem is enlarged and grooved. When the leaf is absent, a u-shaped or v-shaped scar remains.

The leaves are divided into 3 leaflets. The leaflets may be egg-shaped, with the broad portion at the base where it attaches to the leaf stalk, or diamond shaped, broadest in the middle and tapering toward both ends. They taper to a point at the tip. They are 1 to 6 long. The two side leaflets are usually shorter than the central leaflet. The leaflet margins may have shallow lobes, they may have rounded teeth, or they may be entire. They tend to be folded slightly along the midrib, not flat. The upper surface is usually entirely hairless, or there may be a line of curly hairs on the midvein. The lower surface is either entirely hairless or has appressed hairs. In the spring the leaves are glossy and have a reddish tint. Throughout the year young leaves are shiny becoming dull with maturity. In the fall the leaves turn yellow to orange, rarely bronze to red.

Black spots may appear on any part of the plant. The spots are urushiol, the resin that causes allergic reactions. When the plant is damaged urushiol is exuded in an attempt to seal off the damaged area. The resin is creamy, turning brown-red then black with oxidation.

The inflorescence is an elongated, 4 to 16 long, unbranched or sparingly branched cluster with usually fewer than 25 flowers. The flower has 5 yellowish petals.

The fruit is a hairless green berry that turns ivory at maturity. The fruit cluster is compact and erect.

 
     
 

Height

 
 

Up to 60 long

 
     
 

Flower Color

 
 

Yellowish

 
     
 

Similar Species

 
 

Boxelder (Acer negundo) saplings may have 3 (usually), 5 (occasionally), or 7 (rarely) leaflets. When it has 3 leaflets it can be indistinguishable from western poison ivy.

Eastern poison ivy (Toxicodendron radicans ssp. negundo) is a vine, not a shrub. It climbs trees. The stems have aerial roots. The leaf stalks are densely hairy. The leaflets tend to be flat, not folded along the midrib. The inflorescence is 3 to 4 long. The fruit cluster hangs downward.

 
     
 
Habitat
 
 

Dry to moist. Wood edges, prairies, fences, beneath utility wires. Full shade to partial sun.

 
     
 
Biology
 
 

Flowering

 
 

June to August

 
     
 

Pests and Diseases

 
 

 

 
     
 

Toxicity

 
 

The sap of this plant contains the allergenic urushiol. Urushiol is not a single chemical but a complex of five chemicals called alkylcatechols.

Several exposures to the substance may be necessary to impart sensitivity. Research has shown that 85% of all people will develop contact dermatitis after adequate exposure. It usually takes 12 to 48 hours for a rash to develop on a previously sensitized person. In some individuals, a single exposure will cause a reaction. In these individuals, the rash will develop in seven to ten days.

The lesions last 14 to 20 days. Rashes do not spread and are not contagious. Treatment can dry the blisters, reduce swelling, and relieve itching, but will not speed healing.

Contact with the outer surface on an undamaged plant should not cause an allergic reaction unless there is residual urushiol present from a previous injury to the plant or a nearby plant. Contact with a torn leaf, broken or damaged stem or rhizome, or black spot will cause a reaction in those sensitized to urushiol.

 
     
 
Use
 
 

 

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

2, 3, 4, 5, 7, 8, 22, 24, 28, 29, 30.

 
  2/20/2023      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

Common and widespread

 
         
 
Taxonomy
 
  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Subclass Rosidae  
  Superorder Rosanae  
 

Order

Sapindales (soapberries, cashews, mahoganies, and allies)  
 

Family

Anacardiaceae (cashew)  
  Subfamily Anacardioideae (cashews, sumacs, and allies)  
 

Genus

Toxicodendron (poison ivies and oaks)  
       
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

Rhus radicans var. rydbergii

Rhus radicans var. vulgaris

Rhus toxicodendron var. vulgaris

Toxicodendron desertorum

Toxicodendron radicans var. rydbergii

 
       
 

Common Names

 
 

northern poison-ivy

Rydberg’s poison-ivy

western poison ivy

western poison-ivy

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Glossary

Entire

Continuous; not toothed, notched, or lobed.

 

Rhizome

A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

 

Urushiol

Collectively, the five chemicals (alkylcatechols) in the sap of Toxicodendrons that cause allergic reactions in humans.

 
 
Visitor Photos
 
           
 

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Nancy Falkum

 
 

Blooming Poison Ivy

 
    western poison ivy      
 

Dan W. Andree

 
 

Poison Ivy....

I wasn’t sure just what it was but I knelt down to tie a shoe and my knee must have been on some and I got a itchy rash on it. I just washed my knee area and put some stuff for itch on it and it eventually went away. Had also noticed a few small red spots on my ankles that itched. Guessing the same thing. I looked it up and it appears to be poison ivy. It was at Frenchman’s Bluff SNA and seems to be in several different areas throughout that SNA. I have encountered other areas in some woodlands even certain weeds can cause itching. I have actually become immune to some types. The poison ivy irritation didn’t last that long and didn’t spread to any place else thankfully. But probably differs with each individual. I’ll be more careful where I kneel down to tie a shoe when out and about in certain areas.

  western poison ivy  
 

Scott Bemman

 
    western poison ivy      
 

Wander Without Wifi

 
    western poison ivy   western poison ivy  
 

Bill Reynolds

 
    western poison ivy   western poison ivy  
           
 
MinnesotaSeasons.com Photos
 
 

Colony

 
    western poison ivy   western poison ivy  
           
 

Plant

 
    western poison ivy   western poison ivy  
           
    western poison ivy   western poison ivy  
           
 

Inflorescence

 
    western poison ivy   western poison ivy  
           
 

Leaves

 
    western poison ivy   western poison ivy  
           
    western poison ivy      
           
 

Black Spots (Urushiol)

 
    western poison ivy      
           
 

Aboveground Rhizome

 
    western poison ivy      

 

Camera

     
 
Slideshows
 
Toxicodendron
Matt Lavin
  Toxicodendron  
 
About

Shrubs, subshrubs, and rarely vines that produce yellowish white drupes. Montana harbors only one species that is common along riparian corridors and on protected slopes with a south aspect.

 

 

slideshow

       
 
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Attach a video, a YouTube link, or a cloud storage link.
 
 

Wander Without Wifi

 
  SIBLEY STATE PARK - Minnesota. A PAINFUL FAIL!
Sep 11, 2020
 
   
 
About

We thought we were going to show you the natural wonders of Sibley State Park, a park that has been around for over 100 years. However, Mother Nature had other ideas. Please subscribe if you like what you see on Wander Without Wifi.

   
       
 
Other Videos
 
  Blue Asters, Red Ivy
Carl Barrentine
 
   
 
About

Published on Sep 15, 2012

Blue big leaf asters (Eurybia macophylla?) and red western poison ivy (Toxicodendron rydbergii) make their seasonal contributions to our autumnal colors. Photographed at the Turtle River State Park, North Dakota (15 September 2012).

   
  rhus toxicodendron
zebrablu
 
   
 
About

Uploaded on Aug 13, 2011

albero

   

 

Camcorder

 
 
Visitor Sightings
 
           
 

Report a sighting of this plant.

 
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Simply email us at info@MinnesotaSeasons.com.
Be sure to include a location.
 
  Nancy Falkum
6/7/2015

Location: Kellogg Weaver Dunes SNA, Weaver Dunes Unit

Blooming Poison Ivy

western poison ivy  
  Scott Bemman
Summer 2020

Location: Frenchman’s Bluff SNA

I wasn’t sure just what it was but I knelt down to tie a shoe and my knee must have been on some and I got a itchy rash on it. I just washed my knee area and put some stuff for itch on it and it eventually went away. Had also noticed a few small red spots on my ankles that itched. Guessing the same thing. I looked it up and it appears to be poison ivy. It was at Frenchman’s Bluff SNA and seems to be in several different areas throughout that SNA. I have encountered other areas in some woodlands even certain weeds can cause itching. I have actually become immune to some types. The poison ivy irritation didn’t last that long and didn’t spread to any place else thankfully. But probably differs with each individual. I’ll be more careful where I kneel down to tie a shoe when out and about in certain areas.

western poison ivy  
  Scott Bemman
9/15/2020

Location: McCarthy Beach State Park

western poison ivy  
  Wander Without Wifi
9/15/2020

Location: McCarthy Beach State Park

western poison ivy  
  Bill Reynolds
6/1/2014

Location: Pennington Co MN

western poison ivy  
  Bill Reynolds
10/11/2013

Location: Pennington Co MN

western poison ivy  
           
 
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