Ageratina altissima (White Snakeroot)

Plant Info
Also known as:
Genus:Ageratina
Family:Asteraceae (Aster)
Life cycle:perennial
Origin:native
Habitat:part shade, shade; thickets, deciduous woods
Bloom season:July - October
Plant height:1 to 4 feet
Wetland Indicator Status:GP: UPL MW: FACU NCNE: FACU
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 Flower shape: indistinct Cluster type: flat Cluster type: panicle

[photo of flowers] A few to many small flower heads in numerous flat clusters 1 to 2 inches across at the end of branching stems. Flower heads are made up of 10 or more bright white 5-parted disk flowers, each about 1/6 inch across, with protruding white styles. There are no ray flowers (petals).

Leaves: Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are 2 to 6 inches long, 1 to 4 inches wide with coarse teeth all around the edges, a sharply pointed tip, and slender leaf stalk up to 2½ inches long. The leaf base is typically wide and rounded or somewhat heart-shaped, becoming more tapered as they ascend the stem. The underside of leaves are typically hairy along major veins. Stems are green and mostly hairless.

Fruit: Fruit type: seed with plume

[photo of fruit] Flower heads transform to black seeds with silken parachutes attached to carry them away.

Notes:

When I took a walk through the park in mid-September, the woods there were filled with White Snakeroot. It and Canada Goldenrod were about the only things blooming in the woods. The flowers are similar to Boneset, and in fact White Snakeroot used to be in the same genus (Eupatorium rugosum) but has since been reclassified. The leaves are distinctly different between the Eupatorium species and White Snakeroot, so a positive ID is fairly easy.

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More photos

Photos by K. Chayka taken at Long Lake Regional Park, New Brighton, MN, July and September 2006 and August 2009. Other Photos courtesy Peter M. Dziuk taken in Anoka county.

Comments

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

Posted by: Carrie Anne - Minneapolis, MN
on: 2010-08-19 14:45:30

Having just positively identified this as growing in my yard, I also went to do a little more research on it. I learned something very important! It contains tremetol, a toxin that has killed humans (notably Abraham Lincoln's mother), when passed on from cow's milk. There are more details on "milk sickness" here at: http://en.wikipedia.org/wiki/Milk_sickness. I think this is very important to note as I have a 3 yr old, but I also want to maintain native plants in my yard, and now I will know to keep an eye on him around this plant.

Posted by: Mary Beth - Twin Cities
on: 2010-08-28 11:52:11

Many non-native garden and house plants are also toxic when ingested - lilies of the valley, azaleas, hydrangeas. However, white snakeroot has been used to treat snakebite. I taught my son not to touch any plant until he learned which ones were safe.

Posted by: Lisa - Coon Rapids
on: 2011-09-14 08:58:06

This showed up in my yard this summer.

Posted by: T. Stoerzinger - Inver Grove Heights, Dakota County
on: 2012-08-23 10:57:12

White Snakeroot seems to be blooming earlier this year. As of 23 Aug 2012, the plants have been in heavy bloom for a week or more. The summer here has been warmer and wetter than usual. The soil is a south slope, is sandy and well drained. The plants are most dense in shady areas under large burr oaks, but some have ventured out into partly sunny areas in a newly restored prairie.

Posted by: Judith Bechtum, DVM - Rice county
on: 2013-06-29 19:46:48

White snakeroot can cause severe neurological diseas in horses that ingest it.

Posted by: colleen - brooklyn park
on: 2014-08-20 22:40:06

Found this in my yard today and wondering if it atracts wildlife? Butterfly?

Posted by: Tina - Rochester
on: 2014-09-04 15:12:38

I live at the edge of the woods, and there are tons of these growing in my yard this year. Bees seem to love them!

Posted by: Kohoutek - Minnetonka
on: 2014-09-15 22:04:23

Carrie Anne - is your 3-year-old (now 7 years old) a CALF, or do you raise COWS in your front yard for your child to get milk from? What? (We also have this is our yard and love it. I cannot believe the paranoia of mothers today to think that they must "watch their child" around an innocent plant that MIGHT contain a toxin when eaten by cows! When I was a kid, all we worried about was poison ivy, for goodness sake!)

Posted by: Andrew - Apple Valley, MN
on: 2015-09-10 16:56:42

I didn't notice this so much last fall but just starting in Sept 15 I noticed all the white flowers. It is very bright white and fills in the open woods perfectly in my back yard.

Posted by: Joey - Burnsville
on: 2016-09-14 18:33:38

In 2015 we had buckthorn removed from our forest. This year, we noticed white snakeroot growing down our hillside and along the forest floor (Aug/Sept 2016). It did not grow there last year. Found out it is poisonous to cows, horses and goats but that deer won't eat it. Since I have no cows, horses, or goats, there should be no problem in leaving it, at least for the time being. Was told it is MN Native by Prairie Restoration.

Posted by: Connie - Spring Park
on: 2017-09-20 19:31:27

Have these growing in my shade garden for the first time this year. Are they as prolific as Virginia Waterleaf?

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