What does snake root look like?

White snakeroot and boneset

This plant’s common name is White snakeroot. Its scientific name is Ageratina altissima. Here’s another photo of a single plant. If you look closely, you can see that the lower leaves have stalks while the upper leaves do not.

This closeup view shows an upper leaf with a developing flower stalk from the leaf’s axil.

Next, we have the top of the plant with developing flower clusters . . .

The White snakeroot flowers are beginning to bloom . . .

Look closely at the individual flowers of the White snakeroot.

Each tiny flower grows in a flower head (like “flowers within a flower”) which is typical of a plant in the Asteraceae family.

Now here’s an intriguing piece. When I studied White snakeroot, I was struck by its flower which immediately reminded me of Boneset (Eupatorium perfoliatum). Here are two photos of Boneset . . . the first shows the upper part of the plant with its leaves surrounding the stem and with the developing flower clusters:

And this second photo shows the Boneset flower head and flowers up close:

You can see the similarities between the White snakeroot and the Boneset flowers. When I first learned the scientific name for White snakeroot, it was Eupatorium rugosum. And Boneset was (and remains) Eupatorium perfoliatum. With the on-going study and re-classification of plants, White snakeroot was moved from the Eupatorium genus to the Ageratina genus and was given a new species name (altissima).


Sunflower Family (Asteraceae)

Other Names:

Origin and Distribution:

White snakeroot is a native of North America. The plant is currently naturalized throughout southern Canada and all over the eastern half of the U.S. excluding areas in the extreme south. White snakeroot occurs everywhere in Ohio, but it is rarer in the northwest compared with other parts of the state. White snakeroot is a tall plant with rather showy clusters of small bright-white flowers so it is easy to spot in fields, meadows, thickets, woods, waste places, roadsides, lake edges, stream banks, and other shady areas in which it thrives. White snakeroot prefers moist forested areas and rich soils, but plants survive in dry places and may even persist in disturbed areas. The species grows best in basic soils.

Plant Description:

White snakeroot is a 3-foot-tall perennial herb. Distinctive features include opposite leaves, which are coarsely-toothed, rounded at the base, sharply-pointed at the tip, and attached to a long slender leaf stalk (petiole), and flat-topped clusters of small bright-white flowers. Ingesting leaves and stems of the plant produces a deadly condition known as “trembles” in animals, and humans can develop “milk sickness” by consuming milk from affected animals. White snakeroot reproduces by seeds and short rhizomes (horizontal underground stems).

  • Root System:

    The root system includes fibrous, branched roots and tough, knotty rhizomes (horizontal underground stems).

  • Seedlings and Shoots:

    Young leaves are thin, pale green, and have short hairs on the upper surface, edges, and veins. Leaf veins, consisting of the midrib and a simple vein on either side (3-nerved), are easy to discern on both the upper and lower surfaces. Stems and leaf stalks (petioles) of young plants are often purple-stained.

  • Stems:

    Stems are erect, leafy, 2 to 3 feet tall, and much branched near the top. Stems may be solitary or several may emerge in a cluster from the same root system.

  • Leaves:

    Leaves are opposite (2 leaves per node), thin, 2 1/2 to 7 inches long, broadly oval to lance-shaped, and 3-nerved. Larger leaves have a rounded base, sharp teeth around the edge, and taper to a point at the tip. Leaves attach to the stem by way of a slender petiole that is at least 1/4 as long as the leaf.

  • Flowers:

    Numerous flower heads are grouped into loosely-branched, flat-topped clusters arising from the axils of upper leaves. Each flower head is about 1/4 inch wide and contains 8 to 30 bright-white disk flowers.

  • Fruits and Seeds:

    The single-seeded fruits are brown or black, about 1/16 inch long, cigar-shaped, and tipped with a tuft of white hairs (pappus).

Similar Species:

White snakeroot can be separated from other Eupatorium species such as bonesets, Joe-Pye weeds, other snakeroots, and thoroughworts by its distinctive leaves that are opposite, sharply-toothed, 3-nerved, and attached to long petioles.


White snakeroot generally begins to flower in July and continues until September. The weed does not persist in cultivated areas. Plants should be pulled as soon as they appear or mowed close to the ground several times during the season before seeds form. Improving drainage may aid in control of this poisonous plant.


Leaves and stems of white snakeroot plants contain tremetol, which is extremely poisonous. The plant is unpalatable to animals, but they will consume it if other forage is scarce. If sufficient amounts of white snakeroot are consumed, animals develop a condition known as ”trembles” that may cause death. Lactating animals excrete the toxin in their milk, which can then pass to humans drinking the milk. The condition produced, known as “milk sickness”, was common in early colonial times. A great milk sickness epidemic occurred in local areas of the eastern U.S. in the early nineteenth century resulting in many deaths. Abraham Lincoln’s mother, Nancy Hanks Lincoln, was among those who died. Eventually, the toxin in white snakeroot was identified as the cause. The condition is rare today because it is common to pool milk from different areas and herds for commercial production thereby diluting any tremetol present. Meat of animals that eat white snakeroot can also contain tremetol at levels toxic to humans consuming it. Dried plants in hay are toxic but not as poisonous as fresh plants.

Facts and Folklore:

  • Native Americans used the plant as a treatment for snakebites as well as for various diseases.


Scientific Name(s): Aristolochia serpentaria L.
Common Name(s): Aristolochiae Radix, Birthwort, Caulis Aristolochiae Manshuriensis, Herba Aristolochiae Mollissima, mǎdōu líng, Pelican flower, Red River snakeroot, Sangree root, Sangrel, Snakeroot, Snakeweed, Texas snakeroot, Virginia snakeroot

Medically reviewed by Drugs.com. Last updated on Aug 12, 2019.

Clinical Overview


Despite traditional claims of efficacy for snakebite, among other uses, toxicity of Aristolochia extracts precludes their use.

Toxicity of Aristolochia extracts precludes their use.


Avoid use. Aristolochia extracts are toxic. Avoid use in pregnancy.


Avoid use. Aristolochia extracts are known to be toxic. Abortifacient effects of aristolochic acids have been documented in animal studies.

None well documented.

Extracts of Aristolochia are known to be toxic (carcinogenic and nephrotoxic). Safety concerns regarding use of products containing aristolochic acids exist.

Aristolochia extracts are carcinogenic and nephrotoxic.

Scientific Family

  • Aristolochiaceae (birthwort)


The genus Aristolochia (Dutchman’s pipe) comprises more than 300 species of herbs and vines, including A. serpentaria (also known as Virginia snakeroot). Synonyms include Aristolochia convolvulacea, Aristolochia hastate, Aristolochia nashi, and Endodeca serpentaria. “Snakeroot” is a term also applied to the unrelated white snakeroot (Ageratina altissima), rattlesnake root (genus Prenanthes), Canadian blacksnakeroot (Sanicula canadensis), black snakeroot (Actaea racemose), and Sampson’s snakeroot (Orbexilum pedunculatum).USDA 2016

A. serpentaria is a low-growing (up to 0.6 m in height) perennial found primarily in the forests of the central and southern United States. The leaves of the plant are heart-shaped. Its exotic, brownish-purple, tube-like flowers are lined with hairs and possess a foul, fruit-like odor that attracts insects. Insects become caught in the hairs of the flowers, then become covered with pollen while struggling to escape; upon escape, the insect carries the pollen to other flowers, resulting in cross-pollination. The dried rhizome of the plant has been traditionally used as an herbal tonic for its gastric stimulant and diuretic effects.Sharp 2014

Several species of butterfly larvae feed on A. serpentaria, transferring the toxic aristolochic acids of the plant to the adult butterflies for use as a defense mechanism against predators.Pinto 2009, Wu 2000


Aristolochia spp. have been widely and extensively used in traditional Chinese medicine, as well as in England and the Americas. Chewed snakeroot was traditionally applied to wounds and used as a cure for snakebite by American Indians. Colonial and European physicians sometimes used snakeroot for infectious fevers, malaria, and rabies. Use in obstetrics, arthritis, eczema, cancer, and weight loss, and as an aphrodisiac, antiviral, and antibacterial agent has been recorded.Heinrich 2009, Kuo 2012, Luciano 2015, Tang 1992

Toxicity of A. serpentaria was reported as early as 1825; in 2000, the US Food and Drug Administration (FDA) issued a warning regarding preparations containing aristolochic acids.FDA 2014, Stegelmeier 2015 In 2004, the European Union ceased approving herbal preparations containing aristolochic acids. The compound has also been removed from the Pharmacopoeia of the People’s Republic of China.Kuo 2012 However, products containing toxic substances such as aristolochic acids are still available, either on unregulated websites or as adulterants in other preparations.Luciano 2015


A. serpentaria and other members of the genus contain aristolochic acids and associated aristolactams and aporphines; protoberberine-, isoquinoline-, and benzylisoquinoline-type alkaloids; and amides, flavonoids, lignans, coumarins, terpenoids, benzenoids, and steroids. Research has focused on identifying aristolochic acids and associated chemicals because of their toxicity.Duke 1996, Kuo 2012, Michl 2014, Tang 1992

Uses and Pharmacology

Toxicity of Aristolochia preparations precludes their use.FDA 2014


Animal data

Ethanolic root extracts of Aristolochia ringens showed inhibition of solid tumor growth (in vivo in rodents) and were significantly active in leukemia models.Akindele 2015 In vitro, activity against leukemia has been demonstrated with aristolochic acids extracted from other plants.Goun 2002

Clinical data

Research reveals no clinical data regarding the use of Aristolochia spp. in cancer; toxicity precludes use for this purpose.

Other uses

Limited studies in rodents suggest Aristolochia extracts may exert neutralizing effects against certain snake venom.Otero 2000, Shabbir 2014

Potential use of Aristolochia extracts as an insecticide, particularly against the malarial vector Anopheles stephensi, has been investigated.Pradeepa 2015


Toxicity of Aristolochia extracts precludes their use.FDA 2014

Pregnancy / Lactation

Avoid use. Aristolochia extracts are known to be toxic. Abortifacient effects of aristolochic acids have been documented in dogs and rodentsWang 1984; the plant has been traditionally used for this purpose.Che 1984, Ganguly 1986


None well documented. Aristolochic acids have been shown to have antithrombin activity.Goun 2002 In vitro evidence suggests that use with Panax ginseng may increase the renal toxicity of Aristolochia.Bunel 2015

Adverse Reactions

Aristolochia extracts are carcinogenic and nephrotoxic (see Toxicology section).


Based on case reports of nephrotoxicity, including end-stage renal disease and aristolochic acid–related DNA adducts in the renal tissue of some patients, the FDA issued a warning in 2000 regarding the nephrotoxicity and carcinogenicity of herbal products containing aristolochic acids.Duke 2002, FDA 2014 Aristolactams and 4,5-dioxoaporphine derivatives are related chemical constituents also reported to be toxic.Michl 2014

Mechanisms of action of the toxic aristolochic acids have been describedLuciano 2015, Michl 2014, Poon 2015 and associations between aristolochic acid and urothelial carcinoma made based on formation of covalent adducts with DNA, which is rarely caused by other carcinogens.Kuo 2012, Luciano 2015, Yang 2014

Index Terms

  • Aristolochia convolvulacea
  • Aristolochia hastate
  • Aristolochia nashi
  • Endodeca serpentaria

Akindele AJ, Wani Z, Mahajan G, et al. Anticancer activity of Aristolochia ringens Vahl. (Aristolochiaceae). J Tradit Complement Med. 2015;5(1):35-41.26151007 Aristolochia serpentaria. USDA, NRCS. The PLANTS Database (http://plants.usda.gov, July 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA. Accessed July 2016.Bunel V, Antoine MH, Nortier J, Duez P, Stévigny C. In vitro effects of Panax ginseng in aristolochic acid-mediated renal tubulotoxicity; apoptosis versus regeneration. Planta Med. 2015;81(5):363-372.25798640Che CT, Ahmed MS, Kang SS, et al. Studies on Aristolochia III. Isolation and biological evaluation of constituents of Aristolochia indica roots for fertility-regulating activity. J Nat Prod. 1984;47(2):331-341.6539809Duke J. Dr. Duke’s Phytochemical and Ethnobotanical Databases. Agricultural Research Service website. http://www.ars-grin.gov/duke/. Updated June 13, 1996.Duke J, Bogenschutz-Godwin M, duCellier J, Duke P. Handbook of Medicinal Herbs. 2nd ed. Boca Raton, FL: CRC Press; 2002.Ganguly T, Pakrashi A, Pal AK. Disruption of pregnancy in mouse by aristolic acid: I. Plausible explanation in relation to early pregnancy events. Contraception. 1986;34(6):625-637.3829677Goun E, Cunningham G, Solodnikov S, Krasnykch O, Miles H. Antithrombin activity of some constituents from Origanum vulgare. Fitoterapia. 2002;73(7–8):692-694.12490231Heinrich M, Chan J, Wanke S, Neinhuis C, Simmonds MS. Local uses of Aristolochia species and content of nephrotoxic aristolochic acid 1 and 2–a global assessment based on bibliographic sources. J Ethnopharmacol. 2009;125(1):108-144.19505558Kuo PC, Li YC, Wu TS. Chemical constituents and pharmacology of the Aristolochia (mădōu ling) species. J Tradit Complement Med. 2012;2(4):249-266.24716140Letter to Health Professionals regarding safety concerns related to the use of botanical products containing aristolochic acid. Food and Drug Administration website. http://www.fda.gov/Food/RecallsOutbreaksEmergencies/SafetyAlertsAdvisories/ucm111200.htm. Updated June 4, 2014. Accessed January 18, 2016.Luciano RL, Perazella MA. Aristolochic acid nephropathy: epidemiology, clinical presentation, and treatment. Drug Saf. 2015;38(1):55-64.25446374Michl J, Ingrouille MJ, Simmonds MS, Heinrich M. Naturally occurring aristolochic acid analogues and their toxicities. Nat Prod Rep. 2014;31(5):676-693.24691743Otero R, Núñez V, Barona J, et al. Snakebites and ethnobotany in the northwest region of Colombia. Part III: neutralization of the haemorrhagic effect of Bothrops atrox venom. J Ethnopharmacol. 2000;73(1-2):233-241.11025161Pinto CF, Troncoso AJ, Urzúa A, Niemeyer H. Aristolochic acids affect the feeding behaviour and development of Battus polydamas archidamas larvae (Lepidoptera: Papilionidae: Troidini). Eur J Entomol. 2009;106(3):357-361.Poon SL, Huang MN, Choo Y, et al. Mutation signatures implicate aristolochic acid in bladder cancer development. Genome Med. 2015;7(1):38.26015808Pradeepa V, Sathish-Narayanan S, Kirubakaran SA, Thanigaivel A, Senthil-Nathan S. Toxicity of aristolochic acids isolated from Aristolochia indica Linn (Aristolochiaceae) against the malarial vector Anopheles stephensi Liston (Diptera: Culicidae). Exp Parasitol. 2015;153:8-16.25660198Shabbir A, Shahzad M, Masci P, Gobe GC. Protective activity of medicinal plants and their isolated compounds against the toxic effects from the venom of Naja (cobra) species. J Ethnopharmacol. 2014;157:222-227.25291011Sharp J, Whitson M. Aristolochia serpentaria. Virginia Snakeroot. Encyclopedia of Life. http://www.eol.org/. Updated 2014. Accessed Jan 18, 2016.Stegelmeier BL, Brown AW, Welch KD. Safety concerns of herbal products and traditional Chinese herbal medicines: dehydropyrrolizidine alkaloids and aristolochic acid. J Appl Toxicol. 2015;35(12):1433-1437.26152912Tang W, Eisenbrand G, eds. Aristolochia spp. Chinese Drugs of Plant Origin: Chemistry, Pharmacology, and Use in Traditional and Modern Medicine. Berlin: Springer; 1992:145-157.Wang WH, Zheng JH. The pregnancy terminating effect and toxicity of an active constituent of Aristolochia mollissima Hance, aristolochic acid A. Yao Xue Xue Bao. 1984;19(6):405-409.6536147Wu TS, Leu YL, Chan YY. Aristolochic acids as a defensive substance for the aristolochiaceous plant-feeding swallowtail butterfly, Pachilopta aristolochiae interpositus. J Chin Chem Soc (Taipei). 2000;47(1):221-226.Yang HY, Chen PC, Wang JD. Chinese herbs containing aristolochic acid associated with renal failure and urothelial carcinoma: a review from epidemiologic observations to causal inference. Biomed Res Int. 2014;2014:569325.25431765


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medicinal herbsWhite SnakerootAgeratina altissima

Herb: White Snakeroot

Latin name: Ageratina altissima

Synonyms: Eupatorium ageratoides, Eupatorium rugosum, Eupatorium urticifolium

Family: Compositae

Medicinal use of White Snakeroot:

The root is diaphoretic, diuretic, febrifuge, stimulant and tonic. It has been used in the treatment of diarrhoea, gravel and urinary diseases. It has also been used in herbal sweat baths to encourage sweating. A decoction or infusion of the root has been taken to treat a fallen or inflamed womb. The root has been chewed and held in the mouth as a treatment for toothache.

Description of the plant:




2 m
(6 1/2 foot)


August to

Habitat of the herb:

Low woods in river valleys in Texas.

Propagation of White Snakeroot:

Seed – sow spring in a cold frame, only just covering the seed. When large enough to handle, prick the seedlings out into individual pots and plant them out in the summer. Division in spring.

Cultivation of the herb:

Low woods in river valleys in Texas.

Known hazards of Ageratina altissima:

The plant contains tremetol, a complex alcohol, and glycosides. These toxins cause a fatal disease known as ‘staggers’ in cattle. The toxin can be passed through the milk and has caused fatalities in humans who have drunk affected cow’s milk.
Plant information taken from the Plants For A Future.

Garden News Blog

Weed of the Month: White Snakeroot

By Saara Nafici | October 20, 2016

Fall-blooming white snakeroot is that nondescript weed that has been inconspicuously growing in shady spots all spring and summer. You barely notice the one- to four-foot-tall plant with toothy, dark green leaves until suddenly—poof! It’s everywhere you turn, all abloom with fluffy white flowers. One of the last wild natives to flower, Ageratina altissima is a godsend to hungry insects like bees, moths, and flies furiously foraging before the weather turns cold and food becomes scarce.

After blooming, its seeds are dispersed primarily by wind, their fuzzy tails carrying them far and wide. The plant also spreads by rhizomes (underground stems), so you’re as likely to see a colony as a single specimen. Originally a woodland plant, white snakeroot is also perfectly at home in the sidewalks, vacant lots, and shady gardens of Brooklyn.

Sadly, white snakeroot played an unfortunate role in American history. In the early 19th century, European settlers, unfamiliar with the plant, allowed cows and other domestic animals to feed on it. A toxin in the plant called tremetol tainted the cow’s milk, causing sickness and death to those who drank it, calves as well as humans. Milk sickness, as it was called, claimed the lives of thousands of people, including, it is thought, Abraham Lincoln’s mother. Native Americans, who made poultices with snakeroot, knew of its toxic properties, but their botanical knowledge was frequently overlooked by settlers, to their detriment.

Eventually, a frontier doctor in Illinois named Anna Pierce Hobbs Bixby learned of the cause of the sickness from a Shawnee medicine woman. Bixby helped control the disease locally by instructing settlers to remove white snakeroot from their fields, but she too was largely ignored by the medical community, and research confirming the connection between snakeroot and milk was only published much later. Today, for better or worse, industrial agriculture has all but eradicated milk sickness. Since milk from thousands of cows is now combined when processed, the occasional toxin-containing contribution would be diluted to harmless levels.

White snakeroot is most easily identifiable in the fall, when its fluffy white flower heads appear, but it has another distinctive characteristic that appears when it leafs out in spring. Look for elaborate, curving trails on some leaves. These are the work of a species of fly (Liriomyza eupatoriella) that makes white snakeroot its host. The fly lays its eggs on the leaf, and after they hatch, the larvae feed on the leaf tissue, tunneling their way around and creating the beautiful, albeit destructive patterns. Vegetable gardeners may recognize these patterns as the telltale sign of leaf miners that attack their chard, beet, spinach, and tomato plants in much the same way. The intricate tunnels don’t do these plants any good, though white snakeroot seems better able to tolerate them than some other species. Another wondrous peek into the complexities of nature: The same plant that could kill a cow is baby food for a tiny fly!

The Weed of the Month series explores the ecology and history of the common wild plants that most gardeners consider weeds.

Saara Nafici is the executive director of Added Value/Red Hook Community Farm. She is also the former coordinator of the Garden Apprentice Program at Brooklyn Botanic Garden and a longtime activist, feminist, bicyclist, naturalist, and youth educator. Follow her weedy plant adventures on Instagram.

By Steven Foster |

The autumn of 1818 was a difficult period for families in the small Indiana settlement of Little Pigeon Creek. Dennis Friend Hanks, a 19-year old, lived with his maternal grandparents, Thomas and Elizabeth Sparrows who died that fall from the milk sickness. The Sparrows lived on the homestead of their young niece whom they had raised, Nancy Hanks Lincoln along with her husband Thomas, and their children 11-year-old, Sarah, and 9-year-old Abraham. On October 5, 1818, Abraham Lincoln’s mother, Nancy Hanks Lincoln, also died from the “milk sickness” a disease that had only been described in 1810 by Daniel Drake as a brief notice of a “new disease” in Cincinnati. The “milk sickness” was a perplexing fatal disease that took the lives of thousands in the Western frontier in the nineteenth century. It often affected entire families and destroyed communities. The only way to contract the disease was by drinking milk or eating butter. The cause of the disease confounded science into the 1920s.

Attempting to secure milk for his party camped north of St. Louis in 1827, T. L. M’Kenny, Chief of the Bureau of Indian Affairs, was told by a settler that after early spring, people stopped using milk. M’Kenny was among the first to speculate that the milk must be tainted from the cows eating a poisonous weed. By the late nineteenth century one plant, a wildflower, with white, button-like flowerheads less than a 1/2-inch across emerged as a suspect—White Snakeroot. Blooming in late summer and early fall, this native weedy wildflower once called Eupatorium rugosum is now known as Ageratina altissima.

In 1908 a USDA researcher, A. C. Crawford authored a U.S.D.A Bulletin “The supposed relationship of white snakeroot to milksickness or trembles.” He had proven that the dried plant produced no symptoms of milk sickness. Science is not always as it seems. He missed an important clue. Milk sickness only occurred during the growing season before the first frost of autumn. He only tested dried plant material and only proved that the dried plant was inert.

In 1926, another USDA chemist, James F. Couch, showed that fresh—not dried—White Snakeroot caused milk sickness. The following year he isolated the chemical complex—tremetol—as the toxic component. The mystery of milk sickness which claimed Abraham Lincoln’s mother and countless thousands of other settlers had finally been solved.

A version of this story was published in my weekly “Eureka Nature” column in the October 17, 2013 edition of the Eureka Springs Independent Newspaper. I visited friends in Missouri on October 20th. They homestead a rich 80-acre Ozark farm in Douglas County, Missouri. They have goats. One died in the spring of 2013 of what a vet determined was “probably a parasitic infection.” The mother of four children suffered neurological symptoms. The family consumed a gallon of goat’s milk per day. Her husband stopped drinking goat’s milk that spring. It made him feel ill, leading him to the conclusion that he may have an allergy to goat’s milk. It made him nauseous. Once he stopped drinking goat’s milk, his health problems disappeared. The family’s and their livestocks’ collective symptoms, along with the presence of white snakeroot around their farm made me wonder—is milk sickness still with us, confined to small homesteads of back-to-the-landers, with symptoms of both livestock and humans completely unrecognized in modern medicine and thus unreported?

White snakeroot


A clump-forming plant reaching 2 to 4 feet high and 2 to 4 feet wide.
Spreads by shallow-rooted rhizomes or by seed.

Plant Care

Best in part shade to full shade. If grown in sun it requires adequate moisture.
Tolerant of dry shady conditions.
Cut back plants if they get too leggy and again in late fall to prevent seeds from disbursing.

Disease, pests, and problems

No serious diseases
Once thought to cure snake bites but in fact, the foliage and roots are toxic, especially to cattle and humans.

Native geographic location and habitat

Native to dry deciduous woods, borders, open woodland meadows and roadsides from SD to OK and eastern U.S..
C-Value: 4

Attracts birds or pollinators

Bees, wasps, butterflies and moths

Leaf description

Opposite, 2 to 5 inches long and 1 to 3 inches wide; lanceolate shaped leaves with coarse toothed (serrated) margins and pointed tips.
Leaves become smaller as they near the top of the stem. Medium green with pale underside, each with 3 prominent veins on upper surface.

Flower description

Compound (corymbs) or flat-headed clusters of panicles on terminal, slightly branches stems.
Individual flowers are bright white, fluffy and slightly fragrant. Flowers are disk flowers , no petals, and bloom in late summer into fall.

Fruit description

Flower heads develop into black seeds, each with silky hairs to help distribute in the wind.

White snakeroot, Eupatorium altissima (formerly known as Eupatorium ruguson) is found in shaded environments from the Rocky Mountains east and from Canada south through Texas. It thrives in established timber and woodland areas, riparian waterways, and windbreaks that are shady and often moist due to high levels of organic matter in the soil. It does not persist in sunny cultivated areas.

White snakeroot is a herbaceous perennial that normally grows to 3 ft. but can grow as tall as 5 ft. It has short branches with a smooth stem and leaves that are pointed ovals with sharply serrated edges. The leaves are arranged oppositely on the stem and branches. The roots are fibrous with rhizomes and very shallow. Reproduction takes place through either seeds or the rhizomes. The flowers are arranged as a flat topped or domed cluster of small white flowers, with each flower producing a single seed. Flowering takes place during the late summer.

White snakeroot is generally not aggressive enough to be considered a serious weed problem, but if left unchecked for extended periods can become more than just a nuisance. White snakeroot can become a problem if livestock consumes it. White snakeroot has been found to be toxic to all mammals that it has been tested on. All parts of the plant are considered toxic. Livestock may die from eating large amounts of the plant at one time or consuming smaller amounts over a longer period of time. Symptoms of poisoning include muscle tremors and weakness, constipation, and possible death. Nursing livestock that consume white snakeroot will transfer the toxin to their offspring, again resulting in the possible loss of the offspring.

The transfer of the toxin through milk can be an issue for people who consume milk from livestock that have grazed on white snakeroot. This is known as milk sickness. In the early 1800’s, milk sickness resulted in the death of thousands of people, most notably, Abraham Lincoln’s mother in 1818. Prior to the discovery of the plant’s toxic effects, milk sickness was thought to be a late summer/early fall infectious disease and also known as milk fever.

Control of white snakeroot may not be easy. The use of herbicides, both broad-spectrum, such as 2,4-D, and selective herbicides, such as glyphosate are toxic to other neighboring plant species so care must be taken when applications are made. Mechanical control, which includes hand pulling, is most successful when the plants are as young as possible prior to establishing their fibrous roots systems that include rhizomes. Once the rhizomes have developed, control becomes much more difficult. Rhizomes that detach from the roots when the plants are pulled can develop into new plants. Cutting the plants back prior to or during flowering but before seed development takes place will hamper seed development and reduce the amount of seed in the soils seed bank.

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