white snakeroot

(Ageratina altissima var. altissima)

Conservation Status
white snakeroot
Photo by Kirk Nelson
  IUCN Red List

not listed


N5 - Secure

SNR - Unranked


not listed

Wetland Indicator Status
  Great Plains

UPL - Obligate upland


OBL - Obligate wetland

  Northcentral & Northeast

OBL - Obligate wetland


White snakeroot is a 1 to 5 tall perennial forb that rises on 1 to 3 stems from a rough, knotty, fibrous-rooted rhizome. It grows only in shade. It is a late bloomer, one of the last flowers to be seen in the woods in the fall.

The stems are erect or ascending, branched near the top, leafy, and hairless or covered with fine, short hairs.

The leaves are opposite, thin, and egg-shaped to broadly lance-shaped. They gradually taper from above the base to a sharp, drawn-out point forming concave sides along the tip. The bases are often rounded or heart-shaped. They are on ½ to 2½ long leaf stalks. The blades are 1½ to 5 times longer than the leaf stalk. The lower leaves are 2 to 6 long and 1 to 5 wide, becoming gradually smaller as they ascend the stem. They have 9 to 25 sharp teeth on each margin. The upper surface is mostly hairless, the lower surface hairy along the veins.

The inflorescence is a flat-topped to dome-shaped branched cluster. On smaller plants they are compact and appear at the end of each upper stem. On larger plants they are open and also appear on long stalks from the upper leaf axils. The clusters are up to 3 wide and have many flower heads.

Each flower head is about ½ wide and ¼ tall. It contains 12 to 25 disk florets and no ray florets. Each disk floret is about ¼ wide, consisting of a bright white flower tube with 5 long spreading lobes. A white, forked style protrudes from the floral tube well beyond the lobes.

The fruit is a tiny dark achene with a small tuft of white hairs about long.




1 to 5


Flower Color




Similar Species


Common boneset (Eupatorium perfoliatum var. perfoliatum) leaves are longer, narrower, stalkless, fused around the stem at their bases. The flower heads are much smaller. It is usually found in full sun, in prairies and meadows, often in wet areas.

Tall boneset (Eupatorium altissimum) leaves are mostly stalkless or are attached to the stem on short leaf stalks. The flower heads are much smaller. Each flower contains just 5 disk florets. The fruit has a tuft of light brown hairs. It is usually found in full sun, in prairies and meadows.


Moderate moisture. Woodland edges and openings, trailsides. Shade.




Late July to September




White snakeroot is poisonous to livestock. It was unusually abundant in southern Minnesota in 2004. A number of horses in the New Ulm area died in the summer of that year, and it is thought that white snakeroot is the cause.

If white snakeroot is eaten by cows their milk may also be poisonous to humans. The mother of Abraham Lincoln is said to have died from “milk sickness” in the summer of 1818. At the time, the source of the disease was unknown. It was later determined that when a cow eats white snakeroot the toxins collect in its milk. When the tainted milk is consumed by humans, it causes severe lethargy, tremors, vomiting, delirium, and eventually death.


Pests and Diseases


white snakeroot leaf miner (Liriomyza eupatoriella)




Distribution Map



2, 3, 4, 5, 7, 24, 28, 29, 30.









  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  


Asterales (sunflowers, bellflowers, fanflowers, and allies)  


Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Asteroideae  
  Supertribe Helianthodae  
  Tribe Eupatorieae (bonesets, blazingstars, and allies)  
  Subtribe Oxylobinae  
  Genus Ageratina (snakeroots)  




Ageratina altissima (white snakeroot)  

This plant was formerly named Eupatorium rugosum.


Subordinate Taxa






Ageratina altissima var. angustata

Ageratina altissimum

Eupatorium rugosum

Eupatorium rugosum var. chlorolepis

Eupatorium rugosum var. tomentellum

Eupatorium rugosum var. villicaule

Eupatorium urticifolium

Eupatorium urticifolium var. tomentellum


Common Names


common white snakeroot



snow thoroughwort

white sanicle

white snakeroot













A dry, one-chambered, single-seeded seed capsule, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed entirely from the wall of the superior ovary, does not split open at maturity, but relies on decay or predation to release the contents.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

Visitor Photos

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Kirk Nelson


Fort Snelling State Park. Along the edge of the woods near the beach parking area.

    white snakeroot   white snakeroot  

Lost Valley Prairie SNA, Washington County

    white snakeroot      
MinnesotaSeasons.com Photos


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    white snakeroot   white snakeroot  


    white snakeroot   white snakeroot  
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Flower Heads

    white snakeroot   white snakeroot  


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Ageratina altissima (White Snakeroot)
Allen Chartier
  Ageratina altissima (White Snakeroot)  



Visitor Videos

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Other Videos
  Minnesota Native Plant - White Snakeroot (Eupatorium Rugosum)

Published on Aug 29, 2013

This video is of the White Snakeroot (Eupatorium Rugosum), a beautiful native white flower that blooms in late summer.

  Dark Energy Medicinal Plant: White Snakeroot
Living the Hedge Witch Life

Uploaded on Aug 17, 2011

A toxic plant, white snakeroot has a medicinal value in bringing a person out of a faint or stupor with the smoke. The plant, however has caused the death of many a person through milk sickness--a poisoning where a milk animal ingests the poisons of the plant and then a person drinks the milk, now containing the toxin.




Visitor Sightings

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  Brandon Artmann

Location: near Scherman, MN

Abundant in our woods, near Scherman, MN, especially along wood edges.

  Kirk Nelson

Location: Fort Snelling State Park

Along the edge of the woods near the beach parking area.

white snakeroot  
  Kirk Nelson

Location: Lost Valley Prairie SNA, Washington County

white snakeroot  
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