A Complete Guide To White Snakeroot – What You Need To Know!

White Snakeroot is a herbacrous perennial flower native to Eastern North America. Scientifically known as Ageratina altissima, it grows 1-3′ tall in partial shade and average moisture. Blooming white flowers in late Summer to Fall, it provides nectar to numerous pollinators and hosts several moths.

White Snakeroot really is a late bloomer, giving a nice splash of white color to other wise drab or yellow fields, vacant lots, and powerline cuts.[1][2]  In isolation it can be somewhat inconspicuous as the flowers are not overly showy.  So, unless you pass a large colony of these plants in bloom you may not notice it.  But Snakeroot has a somewhat ‘weedy’ nature, as it spreads via underground rhizomes and the seed can readily germinate in disturbed soil. 

Ailanthus Webworm Moth on White Snakeroot

Nonetheless, White Snakeroot provides late season food to bees and butterflies, as well as some moths.  This is a highly toxic plant to all mammals and should not be consumed.[3][4]  Milk produced from animals that have consumed this plant is also toxic to humans.[5]  So, whether you call this a native wildflower or weed likely depends on if you are a farmer.

 White Snakeroot Facts

  • White Snakeroot is hardy from USDA zones 3-8, check your USDA zone here
  • This is one of the latest blooming plants in Autumn.  It may even bloom later than Aromatic Aster.
  • Early colonists and settlers erroneously thought that White Snakeroot could be used to treat snake bites (it is toxic)
  • The poison / toxin contained within White Snakeroot is called tremetol, and is present in the foliage and roots (so don’t consume it). [3]
  • Tremetol can be consumed by grazing herbivores, and be fatal to them.

Scientific Name of White Snakeroot

The Scientific Name of White Snakeroot is Ageratina altissima  or Eupatorium rugosum, as it was previously known.

White Snakeroot Reference Table

Common NameWhite Snakeroot, Richweed
Botanical nameAgeratina altissima  also Eupatorium rugosum
Bloom TimeFall
Bloom DurationApproximately 2 months
Bloom SizeIndividual blooms are approximately ¼”- 1/2” diameter (6 -12 mm).  White in color, but no rays.
CharacteristicsMany individual blooms will occur in a flat-head panicle that is 10-30 flowers.  The overall panicle is between 2-6” diameter (5-15 cm).
Height2-4’ (60-120 cm)
Spacing/Spread2-4’ (60-120 cm)
Light RequirementsPartial sun to Shade
Soil TypesLoam to Clay loam
MoistureSomewhat moist to slightly dry – very adaptable
MaintenanceYou can prune to a shape you like
Typical UseCan be good erosion control in disturbed areas, along tree lines.  It can spread by rhizomes making a colony, so this plant may not be a good choice for manicured flower beds
Fauna AssociationsFlowers are pollinated by various bees, flies, moths, and butterflies.
Larval HostSeveral species of moth caterpillars will feed on the foliage
Sowing DepthSurface sown, light required to germinate
Stratification60 days cold moist stratification.
Native RangeUSDA Zones 3-8
Sources [1]

Native range

The native range of White Snake root is the Eastern half of North America, just about everywhere east of the Rocky Mountains.[1]

The native range or White Snakeroot. Source [1]

Physical Description (Identification) of White Snakeroot

White Snakeroot is a herbaceous perennial that will typically grow 1-3′ tall depending on conditions.[6] However, if it is mowed or trimmed back the height can be reduced to just a foot or two, but will still bloom. This is sort of like giving it the Chelsea Chop.  I’ve done this along the border of a forest in my yard.  In general this plant is very inconspicuous until it blooms in September.

Stalk / Stem

The stalk of White Snakeroot is light green in color, and is generally smooth.  There will be branching in the upper 1/3 of the plant, and more branching where the flower heads form. [6]


White Snakeroot leaves are opposite along the stalk, generally cordate in shape resembling a heart or spade, and are up to 4-5″ long by 3″ wide. Largest at the bottom of the plant, leaves become smaller in size as they ascend the stem.  The margins are serrated or crenate.

An example of White Snakeroot leaves, with this specimen showing some smaller leaflets at the base.


The individual flowerheads are 1/4″-1/2″ diameter, white in color, and very ornate when examined closely, and contain numerous tiny disc florets.  Blooms are clustered in a panicle that is kind of flat headed, similar to Boneset or Wild Parsnip.

Ageratina altissima flower

Each floret has 5 lobes and a long style that protrudes, giving an almost fuzzy appearance.

Close up of White Snakeroot flower.

Seed heads will form in late autumn.  The seed is at the base of a small white hair, and will be spread out by the wind.  The seeds have been found to be viable for approximately 3 years [7]. And although not fully understood, there appears to be a forced dormancy within the seed only allowing germination in Spring after Winter.


White Snakeroot has shallow fibrous roots that are rhizomes.  So, this plant can form colonies.  Particularly in disturbed areas.

Is White Snakeroot Invasive?

In disturbed sites, white Snakeroot can be extremely aggressive as it spreads via rhizome roots.[6]  These rhizomes allow it to establish itself quickly, and colonize / take over an area.  However, in an already established area this plant will find spreading more difficult due to competition from surrounding plants, taking several years to become a problem (in agricultural settings).

How to Control White Snakeroot?

If you graze animals, you should control White Snakeroot as it can kill your livestock. Any milk produced from animals that have consumed White Snakeroot is also poisonous and can kill humans.[5][8] In fact, ‘milk sickness’ was a problem for settlers during initial clearing of land. And the disturbance of forests allowing more sunlight often promotes more White Snakeroot growth/spread.

Mechanical Control of White Snakeroot

Due to White Snakeroot having rhizome and fibrous roots, pulling established colonies of plants will not be effective as new plants will sprout from the Rhizomes readily. 

Pulling young isolated plants is effective, but you may need to do so multiple times.  Repeated mowing White Snakeroot close to the ground over an entire growing season can effectively starve White Snakeroot of sunlight, as it expends all it’s energy stored in the roots.

Chemical Control of White Snakeroot

Using a herbicide that is non-selective is the most effective method of controlling White Snakeroot, and is often necessary for large infestations.  Triclopyr, which the active ingredient of many brush killers is effective for controlling White Snakeroot and doesn’t stay in the soil too long.  I’ve written more details about the time needed for Triclopyr to degrade and break down in our article on killing stumps. So click over there if you want to read more detail.

Where is White Snakeroot found?

White Snakeroot grows readily along the edges of woods, creeks, pastures, and thickets with moderate soil moisture. It is highly adaptable to different growing conditions.

Is White Snakeroot Edible?

White Snakeroot contains the toxic compound Tremetol and should not be consumed.  Many people used to die from drinking milk that was contaminated with tremetol, which wasn’t discovered until 1906.[5]

Is White Snakeroot Toxic

All parts of the plant White Snakeroot are toxic due to the chemical Termetol.  Tremetol has been found to be toxic in just about every mammal that has been studied, from humans to horses.[3][4]  Humans have historically gotten ‘milk sickness’ from consuming milk that was produced by a cow that grazed on some White Snakeroot.[5]  Symptoms of poisoning include tremors, and losing the ability to walk.

White Snakeroot Growing Conditions

Sunlight requirements

White Snakeroot will grow best in partial shade.  I’ve found it along borders of forest, pathways in parks, and up the banks of creeks.  It generally prefers to have loam soil, or clay-loam.

Moisture requirements

For moisture, it is a ‘moderate’ plant.  It can grow in slightly moist to slightly dry conditions, making it highly adaptable for partially shaded areas.

This isolated specimen was along a forested border in a park.

How to care  for White Snakeroot

As a native plant, if grown in it’s preferred conditions no care will be required. It is generally pest and disease free. Although some leaf damage from foraging insects should be expected.

How to Establish White Snakeroot from seed

White Snakeroot seeds need two to three months of cold stratification before germinating. The seed also needs exposure to sunlight to germinate.[9] This is most easily achieved by Winter Sowing White Snakeroot on the surface of the soil.

White Snakeroot seeds that I harvested. These have the ‘feather’ attached.

You can also direct sow White Snakeroot on disturbed areas. Simply scatter seed on the surface of a disturbed area in Fall or Winter, and walk on it to ensure good contact with the soil, but make sure you don’t cover it up.

Wildlife, pests, and diseases


Late season pollinators will greatly utilize this plant, as it is one of the last flowers to bloom until steady frosts set in.  Some of the common pollinators that visit White Snakeroot include sweat bees, leaf-cutter bees, and various pollinating flies.

Sweat bee on White Snakeroot

White Snakeroot is a host plant for several moths including the Eupatorium Borer and Ruby Tiger Moth. Some flies also lay eggs on the plant.

As one of the last flowers to bloom White Snakeroot is ecologically important.

Deer & Rabbits

White Snakeroot is not browsed by deer and rabbits. The toxicity and bitterness of the foliage keeps them away.


White Snakeroot will poison cattle, goats, and other mammals. Symptoms include tremors and vomiting, and can prove fatal for the animal. Milk from animals that have consumed White Snakeroot can be toxic as well, and should not be consumed.

Note that White Snakeroot will still contain the primary toxin, tremetol, after drying. So, even if it is contained within a fully dried hay bale the risk of positioning is still present. [8]

Pests and diseases

No significant diseases seem to affect White Snakeroot.  Most mammal herbivores will not eat this plant due to the foliage being bitter (and filled with toxins).


Garden uses

Due to White Snakeroot’s aggressive nature, it is not a good plant to grow in well manicured flower beds.  It is better suited to wild areas, or areas that are already somewhat established as that will provide some competition.

White Snakeroot is listed as a plant good for roadsides, erosions control, and an excellent border flower. This is primarily due to it’s adaptive and aggressiveness allows it to quickly colonize and establish itself in disturbed areas. [10]

If you have livestock, or live near someone who has livestock, then you should not cultivate this plant.

Native American uses

Note – all parts of this plant are toxic and should not be consumed at all. That being said, Native Americans did use this plant medicinally. The Cherokee and Iroquois both used White Snakeroot as a medicine.[na] Some of the ailments it was used to treat are as follows:

  • Root was used as a diuretic
  • Plant was taken to treat diarrhea and fever
  • Was used to treat kidney stones
  • Root was used to treat venereal disease

Final Thoughts

White Snakeroot is a beautiful flower, but quite aggressive for a smaller garden space. It’s late season nectar is welcomed by the many species of bee that visit it, as well as the caterpillars it hosts.

While this flower is showy in large colonies/patches, it’s aggressive nature make it a flower that is better to admire where it naturally grows, rather than a formal flower bed.

Find more native plants here


[1] – Ageratina altissima, USDA NRCS.

[2] – Summers, Lucy, Border Flowers, London : Headline, 2010, pp129.

[3] – Lee, Stephen T., et al. “Tremetone and structurally related compounds in white snakeroot (Ageratina altissima): a plant associated with trembles and milk sickness.” Journal of agricultural and food chemistry 58.15 (2010): 8560-8565.

[4] – Dubey, Nawal K., et al. “Common toxic plants and their forensic significance.” Natural Products and Drug Discovery. Elsevier, 2018. 349-374.

[5] – Meszaros, Gary, The prairie peninsula, Kent, Ohio : The Kent State University Press, 2017, pp130

[6] – Aniśko, Tomasz, When perennials bloom : an almanac for planning and planting, Portland : Timber Press, 2008, pp515

[7] – Redwood, M., Matlack, G., & Huebner, C. (2016). Seed longevity and dormancy state in a disturbance-dependent forest herb, Ageratina altissima. Seed Science Research, 26(2), 148-152. doi:10.1017/S0960258516000052

[8] – Davis, T. Zane, et al. “Toxicity of white snakeroot (Ageratina altissima) and chemical extracts of white snakeroot in goats.” Journal of agricultural and food chemistry 63.7 (2015): 2092-2097.

[9] – Walck, Jeffrey L., Carol C. Baskin, and Jerry M. Baskin. “Comparative achene germination requirements of the rockhouse endemic Ageratina luciae-brauniae and its widespread close relative A. altissima (Asteraceae).” American Midland Naturalist (1997): 1-12.

[10] – Hess, Anna N., and Julie AM Hess. “Pollinator Restoration through Electric Cooperatives.” American Entomologist 66.2 (2020): 24-27.

[11] – Ageratina altissima. North American Ethnobotany Database. Accessed 06AUG2023.

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over 10 years. I hope to share some of my knowledge with you! You may have seen some of my videos I create on our YouTube channel, GrowitBuildit (more than 10 million views!). You can find my channel here: https://youtube.com/@growitbuildit Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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