Toxicodendron rydbergii (Western Poison Ivy): Minnesota Wildflowers

Toxicodendron rydbergii (Western Poison Ivy)

Plant Info
Also known as:
Genus:	Toxicodendron
Family:	Anacardiaceae (Sumac)
Life cycle:	perennial
Origin:	native
Status:	Noxious Weed
Habitat:	part shade, sun; edges of woods, prairies, open areas
Bloom season:	June - July
Plant height:	6 to 36 inches
USDA PLANTS database:	Minnesota county distribution map
Spotted in Ramsey County at:	Battle Creek Regional Park Long Lake Regional Park Vadnais/Snail Lake Regional Park

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Detailed Information

Flower:

Flowers are in branching spike-like clusters that arise from the leaf axils. Each flower is about 1/16 inch across, 5 greenish white petals and 5 stamens with yellow-orange tips, though they are difficult to see. The spikes may be from 2 inches to over a foot long.

Leaves and stem:

Leaves are compound in groups of 3, each group at the end of a long stem alternately attached on the woody main stem, usually near the top. The leaves spread out over the flowers like an umbrella, often hiding the flowers from view. Each leaflet is up to 6 inches long and 4½ inches wide, generally oval, usually with an abrupt sharp point at the tip and slightly tapering at the base. Some leaves have a few notches on the side, looking like very large teeth. The leaf surface is a bit shiny.

Fruit:

Fruit is a smooth, round, dull white to yellowish berry about 1/8 inch in diameter. The berries persist through the winter (this photo taken in January).

Notes:

Western Poison Ivy is on the noxious weed list for Minnesota due to its toxic, rash-producing properties, as well as its somewhat aggressive growth. It is actually categorized as a shrub because of the woody main stem. 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 main 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.

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More photos

Photos taken at Long Lake Regional Park, New Brighton, MN January and May-June 2008

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.