Toxicodendron radicans (Eastern Poison Ivy)
|Also known as:||Common Poison Ivy|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; floodplain forest|
|Plant height:||shrub to 6 ft, vine to 60 ft|
|Wetland Indicator Status:||GP: FACU MW: FAC NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Branching clusters, usually loosely arranged, to 4 inches long arising from leaf axils near branch tips, with male and female flowers on separate plants. Flowers are about ¼ inch across, yellowish-green to greenish-white with 5 petals. Male flowers have 5 stamens alternating with the petals, female flowers have a rounded ovary in the center with a 3-lobed style at the top. The 5 sepals cupping the flower are green and hairless. Flower stalks are densely short-hairy.
Leaves and stems:
Leaves are compound in sets of 3, each group at the end of a long stalk alternately attached to the woody main stem. Leaflets are 3 to 7 inches long, 2 to 4 inches wide, generally oval to egg-shaped, pointed at the tip and rounded or tapering at the base. The end leaflet is largest and long stalked, the 2 lateral leaflets short stalked. Leaflets may be toothless or have a few large teeth or shallow lobes, sometimes just on one side. The upper leaf surface is sparsely covered in appressed hairs, the underside lighter in color and more densely hairy especially along major veins. Leaf stalks are covered in short hairs. New leaves are initially tinged a bronzy color, becoming dark green, then turning red in fall.
New branches are green and hairy, becoming gray-brown and hairless the second year, with slightly rough bark. Plants can grow shrub-like with stems up to 1 inch diameter at breast height, or as a climbing vine with a trunk 2 or more inches in diameter and numerous aerial roots that latch onto tree bark for support.
Eastern Poison Ivy, along with its sibling Western Poison Ivy (Toxicodendron rydbergii), is on the noxious weed list for Minnesota due to its toxic, rash-producing properties. Unlike its ubiquitous sibling, however, Eastern Poison Ivy is uncommon in the state, limited to floodplain forests of our eastern-most counties from the Metro south and does not appear to be as aggressive a spreader here as it is farther east. While the leaf shape is like Western Poison Ivy, Eastern Poison Ivy has hairy leaf stalks and hairier leaves and its growth habit is either more branching and shrub-like, or vining which Western Poison Ivy never does. There are 6 recognized subspecies of T. radicans, 4 of which have limited ranges in the south or southwestern US. The 2 most common are subsp. radicans, present to our east and south, has hairless leaf stalks, and subsp. negundo, described above, with its population centered in the Midwest and found in Minnesota. Note that the national distribution maps (both BONAP and USDA) do not have accurate county-level information for this species in Minnesota.
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- Eastern Poison Ivy vining plant
- Eastern Poison Ivy more shrub-like plant
- fall color
- loaded with berries
- a high-climbing vine
- early leaves are bronzy
- stems climbing over a rotting tree
Photos courtesy Peter M. Dziuk taken in Winona County and in Michigan.
Have you seen this plant in Minnesota, or have any other comments about it?