Toxicodendron rydbergii (Western Poison Ivy)
|Also known as:|
|Life cycle:||perennial woody|
|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):|
|National distribution (click map to enlarge):|
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Leaves and stem:
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.
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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Where to buy native seed and plants ↓
- Poison Ivy plants
- early spring sprouts
- fruit in winter
- flowering plant
- fall color
- a colony of Western Poison Ivy
Photos by K. Chayka taken in Ramsey County. Photos courtesy Peter M. Dziuk taken in Anoka and Hubbard counties.
Have you seen this plant in Minnesota, or have any other comments about it?