Toxicodendron rydbergii (Western Poison Ivy)

Plant Info
Also known as:
Genus:Toxicodendron
Family:Anacardiaceae (Sumac)
Life cycle:perennial woody
Origin:native
Status:
  • Noxious Weed
Habitat:part shade, sun; moist to dry; open woods, fields, roadsides
Bloom season:June - July
Plant height:6 to 48 inches
Wetland Indicator Status:GP: FACU MW: FAC NCNE: FAC
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 5-petals Cluster type: panicle

[photo of flowers] Flowers are in sparsely branching clusters 2 to 12 inches long that arise from the leaf axils. Each flower is about 1/16 inch across, 5 greenish white petals and 5 stamens with yellow tips.

Leaves and stem: Leaf attachment: alternate Leaf type: compound

[photo of leaves] Leaves are compound in groups of 3, often drooping, each group at the end of a long stalk alternately attached to the woody main stem. Leaflets are up to 6 inches long and 4½ inches wide, generally oval to egg-shaped, pointed at the tip and rounded or tapering at the base, often folded along the midrib. The end leaflet is stalked and usually largest, the 2 lateral leaflets stalkless or short stalked. Leaves may be toothless or have a few large teeth, sometimes just on one side. The upper leaf surface is hairless and shiny, becoming dull with age; the underside is lighter in color with a few hairs along the midvein. New leaves are initially tinged a bronzy color, becoming dark green, then turning yellow to red in fall. The woody stem is hairless and usually erect and unbranched.

Fruit: Fruit type: berry/drupe

[photo of fruit] Fruit is a round, green berry turning dull white to yellowish and about 1/8 inch in diameter. The berries persist through the winter.

Notes:

Western Poison Ivy is on the noxious weed list for Minnesota due to its toxic, rash-producing properties, as well as its propensity to form large colonies from underground rhizomes. It has a preference for drier, sunny spots but grows well enough in shadier and moister soil and seems to thrive along trail edges. While it can grow to 4 feet tall, it is more typically 1 to 2 feet. It is not to be confused with other plants having leaves in 3's on long stems: Jack-in-the-pulpit, various species of Trillium, or Wild Sarsaparilla. Poison Ivy's woody lower stem is a distinguishing feature, the vein pattern and/or shape of the leaves is different than those other plants, and the flowers are easily recognizable when the plant is in bloom. When in doubt, the old saying "leaves of 3, let it be" is good advice.

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More photos

Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka and Hubbard counties.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Joanne W
on: 2009-06-13 16:41:52

I've had this plant growing on the edge of a stand of trees for about 4 years now. I've been trying to identify it. When I saw these photos (western poison ivy) on your site I think I may have found it. It looks exactly like it. I wasn't sure it was poison ivy because it doesn't "vine" at all, it disappears completely every winter, and (most importantly)no one has ever had any reaction to touching it. We rip it out bare handed every year. It grows like a rhizome so we pull out long bunches. I cannot find any yellow or orange on the flowers at all, and it only gets a few berries. We thought maybe this is because it gets very little sun. My horses eat it with no problems. Is it possible this is weak kind of poison ivy?

Posted by: K Chayka
on: 2009-06-13 16:44:38

Don't let the name fool you--poison ivy is not a vine. I have touched it many times myself and rarely get a rash from it. It may be some people are just more sensitive to its effects than others. It does spread through rhizomes, which is why it's an aggressive breeder.

I can't really comment on the horses, but you could probably find more info on that using your favorite search engine.

Posted by: Gabe - Goodhue County
on: 2014-08-18 11:32:59

Indeed, Western Poison Ivy is little more than a ground cover, but there is the other species, Eastern poison-ivy (Toxicodendron radicans) that is often a very impressive vine in floodplain areas; its conspicuous aerial roots are notable climbing up floodplain trees in . It is considered the "rare" poison-ivy in MN, but I believe it to be more widely distributed (especially along the Mississippi and it's major tributaries) than is reported (the PLANT Database has a poor distribution map). I have seen it plentifully along the Mississippi shoreline in my area and below Lake Pepin.

Posted by: Mike - Elk River
on: 2014-10-02 01:41:19

Regarding comments above, pulling bunches barehanded - I have been in the company of people who mistook hog peanuts and other plants (baby hop trees, beggarticks, even small boxelder) for poison ivy, even with pictures in front of them. The risk is that one may come to believe oneself immune based on common misidentification , and get a bad surprise one day. The pictures of the berries and flowers here (nice job, guys) should be consulted as well as the leaves, if in doubt and handling such plants. It is also common to develop increased sensitivity to the oil over time, with repeated exposure - and immunity to that stuff is valuable, not to be risked unnecessarily. You might not want to handle the plant with bare hands, regardless of immunity, especially in the spring when it is oily (shiny leaves). The horses I've met can eat poison ivy, and some prefer it.

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