Ageratina altissima (White Snakeroot)

Plant Info
Also known as:
Family:Asteraceae (Aster)
Life cycle:perennial
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.


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.


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: 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?

Posted by: Helen - Southeast
on: 2018-05-15 05:54:14

I have heard that the meat of animals that ingest this plant is also toxic. I have a huge amount of it, along with lots of nettle, which I eat as a cooked green, and which it resembles when first emerging in Spring, so that was a bit worrisome, growing in an area that we recently cleared of an impassable tangle of broken boxelders, wild grape, thorny ash, buckthorn and others. I had been thinking of running chickens and/or pigs in this area, but am concerned that their eggs/meat may become toxic. Many people were sickened and died from this plant in the days when people used cattle to help clear their woodlots.

Posted by: Caleb Smith - Peacebunny Island, Mississippi River island
on: 2018-08-09 12:32:43

After a two late floods, we saw clusters emerge this week on the west side of the island, closest to the main channel at Newport, MN

Posted by: Annie - Sunfish Lake, MN
on: 2018-10-07 11:19:52

When visiting a dear friend (August) in Sunfishlake, MN these were every where. Last summer when visiting, I didn't see any of these. Are they an invasive species? Will they take over eveything else? We like to exploor the woodsy areas there and look for different plants and wildlife. Someone earlier mentioned they could be toxic? Are they harmful to dogs?

Posted by: K. Chayka
on: 2018-10-07 12:41:08

Annie, white snakeroot is a native woodland species so no, it's not invasive in its usual habitat, though, like many natives, it can be a bit aggressive in cultivation. I don't know how toxic it is to dogs.

Posted by: Gary - Carlton County
on: 2018-10-19 19:17:46

Saw a small plant with flowers on September 24th this year on the Munger Trail in Moose Lake. I took a photo of the plant with flowers and upper leaves which are narrower than the lower leaves.

Posted by: Evie - St Anthony Village
on: 2018-12-12 21:42:18

This plant popped up on my partial shade south-facing slope. I'm relieved to learn it's a native, because I enjoyed the mass of bobbing white flowers this fall. I've been pulling Creeping Bellflower from the area, so it's encouraging to get something free that belongs there. It's a start to going native on my urban lot. I also have young children, but they only eat what I specifically teach them to eat outside.

Posted by: Mike - Bloomington
on: 2019-05-09 19:39:16

Several years ago I was happy to see this appear in my garden. Eventually tall robust plants were everywhere. Last year I began controlling it, removing every flower head before they could go to seed.

Posted by: Bill Brown - Grant
on: 2019-08-29 10:57:59

I'm seeing quite a few of these. They are new to a woodland I recently opened up by removing a buckthorn infestation as well as a lot of boxelder trees. I find the white flowers bright and reasonably attractive, better than many, bare dirt, and solid green. Concerned mostly about native landscape aesthetic and ecology, I think I'll leave them for now but Mike in Bloomington's experience has me on guard for over proliferation. Sure hope my decision doesn't lead to a lot of control work in the future.

Posted by: Jacque Behrens - south Minneapolis
on: 2019-09-14 21:29:24

Have an area of my yard that I removed a tree, some buckthorn and other vegetation last fall and a few of these have just come into flower in the partial shade that remains. Read in the Prairie Moon Nursery description that it may seem weedy after a soil disturbance but does play well with other plants so I'm going to leave it be for now.

Posted by: Kathy & Doug Wood - Stearns county north of Sartell in our woods sling the Zmi
on: 2020-02-13 02:58:27

These have really spread the last couple of years in our woods.

Posted by: Lynne Renz - Eagan
on: 2020-08-31 18:24:37

Just showed up this year. Since we put in a rain garden we've had several "guests" appear, first a forget me not, then a New England aster, then a spiderwort, and now a snakeroot.

Posted by: Becky DeLaCruz - Minnetonka
on: 2020-09-09 10:36:05

This has gone crazy in our yard this year, and don't recall seeing it before this late summer 2020. We have a very large area of coneflowers (about 60 x 20 feet) and the snakeroot actually began to take over that area the past 2-3 weeks. We have now pulled out and tried to get rid of as much of it as possible.

Posted by: luciearl - Lake Shore
on: 2020-09-12 07:56:08

This is a welcome site at the end of the flowering season.Lining the edge of my woods, the outline has spread. I'm not concerned because I don't have cows or horses in my yard. Native animals just seem to know what native plants they can eat.

Posted by: Scott - White Bear Lake
on: 2020-10-04 20:02:32

One of our favorites on the hill going down to the marsh, in our back yard.

Posted by: Paula Hunt - South East
on: 2020-10-06 22:51:57

White Snakeroot, yes,is "native" to Minnesota, but it killed thousands of settlers too. Some people say that it is harmless and that animals will not eat it.THIS IS NOT TRUE. This plant contains a deadly toxin, Tremetol. It is not the FIRST choice for forage. Most animals, when they run out of other options in their pasture, will eventually eat this as a last resort. Some older healthier livestock may live, but their meat and milk is toxic. They will abort. Their babies drinking milk, and elderly animals will die.

When I say livestock, I am referring to all animals, horses, cattle, sheep, goats, chickens, and wild animals as well have been known to succomb to tremetol poisoning when they times where lean and they inadvertently ate of the white snakeroot plant as well. Animals depend on US to protect them.

There is still NO CURE for Tremetol poisoning. It is a horrible way for anything to die. If only a small amount is ingested. People, live with horrific irreversible damage. This plant may LOOK pretty in your yards, but birds spreading seeds could be making sick, or killing your friends, and family, or their livestock, and anyone who eats meat or milk from a small family run organic farm. Thank you for respectfully,for listening.

Posted by: K. Chayka
on: 2020-10-09 13:26:22

Paula, I've considered your points but think some need qualification. First, if this plant is on your own property and you have livestock or children you are afraid will consume it, then perhaps you should remove it. Also, provide your livestock with sufficient forage and teach your children to avoid it. But to suggest clearing it from natural areas or that no one should garden with it is a bit alarmist. There are many deadly poisonous plants in the world, including rhododendrons and azaleas, and you'd be hard pressed to convince the nursery trade to stop selling them.

As for native wildlife, they've cohabitated with white snakeroot for millennia and I don't believe there have been any extinctions due to this plant. What may have happened to settlers in centuries past isn't really relevant in today's world.

One other point I'd like to make is that humans have generally done a poor job of caring for natural areas, and local ecologies are negatively affected because of it. White snakeroot is an opportunist, often filling in gaps where other plant species may have disappeared due to invasive species, destruction from human activities, and even climate change. If you want to see its numbers diminish, why not work on restoring ecological balance to degraded areas? Would that not be a good solution?

Posted by: JK - Mahtomedi
on: 2021-08-17 11:39:36

Found a tall white flowering plant under my lilac bushes. Probably started from bird droppings. Identified as White Snakeroot. The really small white flower clusters are beautiful! I love the protruding white styles! So glad I didn't pull this lovely 💗

Posted by: Kristin Ammerman - Stillwater
on: 2021-08-29 19:32:07

White Snakeroot showed up en mass in my wooded area. It's easily 4 ft tall and fills a 15 x 12 foot area.

Posted by: Lolly - Lake Crystal
on: 2021-09-02 09:53:12

White Snakeroot: this plant showed up in a part of my farmstead that I recently had removed buckthorn, boxelder, cottonwood and mulberry from. there is a patch about 10-12 feet around, some plants are 3-4 feet high. it should get more sunlight now. I do not have any livestock, so I plan to let it go and see what happens.

Posted by: Elysia - St. Paul
on: 2021-09-12 12:16:07

This plant grows all along the Mississippi river near Hidden Falls and Watergate Marina in St. Paul, probably lots of other places too. Note for those with tall plants in their yards -- check to see if it's boneset instead, the flowers are similar but the leaves are quite different. Boneset grows much larger, can even look like a small bush, and the flowers spread out wide above the plant, while snakeroot tends to be concentrated at the top.

Posted by: Sharon in St Paul - Central
on: 2022-08-29 18:10:47

So happy to find out this is native. It started showing up in our yard 3 years ago. It is starting to spread somewhat more aggressively due to an unintentional disturbance in the soil along a forest edge. I can see that it warrants some control. Will keep an eye on it. Since we're not in Wisconsin, and if you've done any driving around the Metro 4th and 5th ring suburbs you know this -- there are no dairy farms around here. However there are many in Wisconsin. So hopefully people there are controlling it a little bit, but I don't think the concern is relevant to Minnesota. Notwithstanding further comments, we have very few dairy farms in MN, especially compared to 50 years ago.

Posted by: Andy - Minneapolis
on: 2023-05-19 15:11:20

Growing in my yard in a 90% shade area under a roof edge/dripline.

Posted by: Chris H - St. Paul
on: 2023-07-14 21:00:01

Funny comments. Let it be it's natural. Yes and no. If you don't have livestock and neighbors don't have livestock no problem. I however do. This plant showed up 2 years ago. Just a couple plants. No worries. Looked kinda pretty. They following year this plant had spread...a lot. I was curious why my goats wouldn't eat it. I identified it and the battle began. However by this time it was fall and the plant was already going to seed and it was too late. This year it has completely taken over the pasture. I don't like herbicide so I have literally pulled by hand over 3 acres and thousands of plants. Now let's go back to the neighbors with livestock part. The wind always blows east to west through the clearings in the woods and pastures. I can trace this plant back half a mile through the clearings. It travels...far. I'm not saying this is just an evil demon plant. I am saying it's nothing to play around with if you have livestock. Take or leave it

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