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University Library, University of Illinois at Urbana-Champaign

Plants Toxic to Animals

D

Datura stramonium L. (Jimsonweed)

Other common names: Jamestown Weed, Thorn Apple, Devil's Trumpet, Mad Apple, Stink Weed
Description

Jimsonweed is a stout, coarse annual herb 2 to 5 feet tall, with spreading branches. It has a pale-green stem and large, ovate, green or purplish, strong-scented leaves, coarsely toothed on their margins. Its flowers are large, white, and tubular, 2 to 4 inches long, and set on short stalks in the axils of branches. Its circular seeds, about 1/8 inch across, are contained in a hard, prickly capsule which, when ripe, splits lengthwise into four parts.

Distribution

Jimsonweed is sometimes grows in cultivated fields, overgrazed pastures, and waste lots. It prefers rich soil and may be found throughout Illinois as well as other states from New England to Texas and Florida.

Conditions of Poisoning

All parts of the Jimsonweed are poisonous, but because of its strong odor and unpleasant taste, animals rarely eat enough of the green plant to be poisoned. Poisoning in animals occurs primarily when hungry animals are turned into a Jimsonweed-infested area where better forage is absent. Most cases of animal poisoning result from a quantity of the dried plant being fed in hay, while poisoning in chickens is due to eating of the seeds. Occasionally Jimsonweeds are accidentally included when the silo is filled. When the silage is fed to the animals poisoning occurs.

Jimsonweed is also known as Jamestown weed because of the mass poisoning of soldiers in Jamestown, Virginia in 1676. Jimsonweed poisoning is more common among humans than in animals.

Control

Hungry animals should never be allowed to graze where there is Jimsonweed. In meadows where the plant grows, hay should not be made until after all Jimsonweeds have been removed. The custom of destroying this plant should be practiced on all farms. 

Toxic Principles

Tropane alkaloids:

  • Hyoscyamine = an isomer of atropine.
  • Scopalamine = L-hyoscine = epoxidized hyoscyamine. 
Clinical Signs

Early signs of poisoning include: rapid pulse, rapid breathing, dilated pupils, restlessness, nervousness, muscular twitching, polydipsia, frequent urination, diarrhea, depression, anorexia, and weight loss. In fatal cases the pulse remains rapid but weak, breathing becomes slow and irregular, body temperature becomes subnormal, urine may be retained, and convulsions or coma precede death.

  • In cattle: excitability, tremors, rumen atony, nervousness, bloat, tenesmus, and anorexia. Death occasionally reported.
  • In goats: Datura stramonium ingestion was accompanied by tachypnea, tremors, drowsiness, recumbency, and altered locomotion.
  • In sheep: Datura stramonium ingestion was associated with ataxia, inability to stand, tachypnea, reduced drinking and mild tremors.
Animals Affected

Cattle, goats, sheep

Delphinium tricorne Michx. and other species (Larkspur, Dwarf and Other Larkspurs)

Dwarf LarkspurDefinition

Dwarf larkspur is an erect, little-branched herb 1 to 3 feet tall. Its leaves, alternately placed and slender-stalked, are deeply divided into 5 to 7 nearly separate lobes, each lobe itself again rather deeply lobed or toothed. Its stout stem ends in a flower-bearing part that carries several blue or white, spurred blossoms 1 to 1 1/2 inches long. Three short-pointed rather fragile, widely spreading pods about 1/2 inch long develop from each blossom. These pods contain numerous small, dark seeds.

The rocket larkspur (Delphinium ajacis L.), which is cultivated and sometimes escapes, may be recognized from the above general description. It is supposed, in common with all other larkspurs, to be poisonous.

Distribution

The dwarf larkspur occurs principally in the southern third of Illinois, where it is most often found in ravines and along streams in wooded sections. Northward it becomes less frequent and probably does not grow in the northernmost two or three tiers of counties.

The rocket larkspur, also, is most abundant in southern counties, where it is most often found in open woods and fallow fields.

Conditions of Poisoning

Larkspurs are among the early spring plants, blossoming in late April and May. Animals turned out to graze in woods in the spring may eat the plant, especially if other herbage is scant. Cattle are the animals most often poisoned. Horses are susceptible to the poisoning but generally avoid larkspurs. Sheep, although seemingly resistant, can be poisoned by large amounts. Fatal poisoning of an animal may result from a single day's consumption of 1 percent or less of the animal's body weight of larkspur plants.

Control

Animals, especially cattle, should not be grazed in woodland pastures infested with larkspurs until there is an abundance of other herbage for them to browse. Heavily infested pastures probably should not be used until the larkspurs have been destroyed. In woods, where it is hard to use chemical weed-killers, the only way to eliminate the plant is to dig it out by the roots. 

Toxic Principle

Although larkspurs contain several other alkaloids, the main poison is the glucoside delphinin. 

Clinical Signs

Symptoms of larkspur poisoning vary according to the amount eaten and the animal's tolerance of the poison. Small amounts may cause loss of appetite, excitability, staggering, or muscular incoordination, and constipation. Severe symptoms include slobbering, nausea, vomiting, colic, bloating, and convulsive movements. Fatal poisoning brings convulsions and paralysis of the respiratory system. Autopsies reveal inflammation, or at least congestion of the windpipe, stomach and small intestine, congestion of the superficial blood vessels, and dark, extremely congested kidneys.

Animals Affected

Cattle, horses, sheep, dogs, cats

References Used

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/larkspur

Dicentra cucullaria (L.) Bernh. & Dicentra canadensis (Goldie) Walp. (Dutchman's Breeches & Squirrel Corn)

Description

Dutchman's Breeches is a low, delicate herb, with slender leaf stalks and flower stalks, both rising from an underground, scaly bulb. Its lacy leaves are 3-parted and finely divided. The flower stalks are 5 to 10 inches long and bear several nodding blossoms 1/2 to 3/4 inch long. The blossoms are odorless, white, and flattened; their peculiar shape suggests the common name of the plant. Seeds are produced in small spindle-shaped pods.

A closely related Dicentra Canadensis (squirrel corn) grows 6-12 inches tall from a horizontal rhizome with small round tubers at the base of the plant. Below ground it has a long rootstock bearing yellowish flattened, orbicular corms. Other than the fact the spurs of D. canadensis are short and not divergent, the two species of Dicentra are very much alike, except that squirrel corn has fragrant flowers.

Distribution

Both Dutchman's breeches and squirrel corn occur throughout the state in wooded areas. Dutchman's breeches is in many places abundant, especially on wooded slopes that have well-drained soil and rich deposits of leaf mold. Squirrel corn, although preferring the same habitat, is much rarer.

Generally Dicentra spp. grow naturally in rich, moist woodlands of eastern to midwestern North America, ranging from New York and southern Ontario to northern Alabama and as far west as eastern Kansas and Nebraska.

Conditions of Poisoning

All parts of the plants are poisonous, and poisoning can occur through ingestion or skin contact. Poisoning generally only occurs after ingesting large amounts of the plant, and skin irritation caused by the plant is minor and quick to fade.

Control

Where Dutchman's Breeches is abundant in pastures, keep cows out until other forage is plentiful -- usually late in May. Let sheep graze infested pastures first. Although Dutchman's Breeches is hard to destroy, heavy grazing by sheep is reported to nearly rid woods pastures of this pest.

Toxic Principle

Isoquinoline alkaloids.

Clinical Signs

Eating the leaves and roots produce poisoning similar to that of Bleeding Heart, a common garden plant. The most common symptom of poisoning by Dutchman's breeches and squirrel corn is a staggering gait, which gives the common name staggerweed to both plants. After eating these plants, cows give less milk.

Experimental feeding of these plants to steers caused sudden trembling which increased in severity, frothing of the mouth, ejection of partially digested stomach contents, and convulsions. The eyes became glassy, and the animals went down and moaned as if in pain. Death from Dutchman's Breeches poisoning is rare, particularly if animals are kept away from the plant after the first symptoms appear.

Animals Affected

Cattle

References Used

https://plants.ces.ncsu.edu/plants/all/dicentra-cucullaria/

Digitalis purpurea L. (Foxglove)

Description

Foxglove is an erect herb found as a weed or as a cultivated ornamental grown in gardens. It typically grows up to approximately 5 feet tall. The leaves are alternate and the flowers are showy, pink, and bell-shaped. Flowers grow terminally on the stem on elongated racemes.

Distribution

Foxglove currently grows in the northwest states of the United States. It prefers rich soils and commonly grows along roadsides, fences, in open clearings in the woods, and in unused areas.

Conditions of Poisoning

Poisoning occurs when the plant is eaten. Livestock are infrequently poisoned, but will eat the plant occasionally either fresh or in hay. The plant remains toxic when dried.

Control

Do not allow animals to graze in areas where foxglove is present. The plant can be removed by pulling it from the ground, although you should be careful to remove all roots and to not shake seeds onto the surrounding soil. Use a waste bag to hold the removed plants to further contain the seeds. Process may take multiple seasons to remove all traces of foxglove from the area.

Toxic Principle

Cardiac glycosides such as digoxin, digitonin, and digitoxin are in all parts of the plant. 

Clinical Signs

Symptoms of poisoning include dizziness, vomiting, diarrhea (possibly bloody), irregular heart beat, weakness, stupor, and delirium or hallucinations. Poisoning can be fatal.

Animals Affected

All animals and humans are susceptible to varying degrees.

References Used

Burrows, George E., & Tyrl, Ronald J. (2013). Toxic plants of North America. Hoboken: Wiley-Blackwell.

E

Equisetum arvense L. (Horsetails)

Description

Herbaceous, perennial, leafless plants with hollow stems that readily separate at the nodes. The leaves are reduced to papery scales with black tips that surround the stems at each node. The stems are cylindrical, ridged and rough to the touch owing to the high silicate content. There are two types of stem, fertile and infertile. Fertile stems are unbranched, and are tipped by a cone-like structure containing spores. Infertile stems have multiple whorled branches at the nodes. The plant reproduces from a deeply buried rhizome and from terminal spore bearing cones. (Colorado State University's Veterinary Teaching Hospital's Guide to Poisonous Plants)

Distribution

Horsetail is a weed that grows in sandy soils in fields, ditches along roads, and along the banks of rivers. There are six species growing in North America, and they tend to prefer cooler, moist growing conditions. 

Conditions of Poisoning

Plants are toxic at all stages and remain toxic when in hay. Young horses are most susceptible to Equisetum poisoning. Plant is rarely eaten except when dried in hay. Hays containing 20% horsetail or bracken fern will result in thiamin-deficiency symptoms in 2-5 weeks.

Control

Animals suspected of being poisoned by horsetail varieties should be taken off of hay or pasture containing the plant and fed a nutritious diet that includes cereal grains rich in thiamine. Treatment with a large dose of thiamine hydrochloride (3-5 mg per kg of body weight) intravenously followed by several days of thiamine intramuscularly (1-2 mg per kg of body weight) provides rapid recovery and restores thiamine levels to normal.

Toxic Principle

Thiaminase is the suspected toxin. Also contains aconitic acid and polustrine, and silicates. All species of Equisetum should be considered potentially toxic to animals until proven otherwise. 

Clinical Signs

Initial weight loss followed several weeks later by incoordination of the hind legs. Diarrhea may also occur before the onset of weight loss and incoordination. Affected animals become progressively weaker and eventually recumbent, and staggers and tremors may be seen. Serum pyruvate levels increase while thiamin levels are depleted. Once horses are down and cannot get up, they usually die within 1 to 2 weeks. Cattle poisoned with horsetail generally show weight loss, decreased milk production, diarrhea, and hyperexcitability.

Animals Affected

Horses, cattle, sheep

Resources Used

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

Eupatorium rugosum Hout. (Snakeroot, White)
(formerly known as Eupatorium urticaefolium)

Description

White snakeroot is an erect, branched herb usually about 3 feet tall but varying from 1 to 5 feet. It has slender, round stems and branches bearing pointed, oval, oppositely placed leaves. These leaves, 3 to 5 inches long and petioled, are sharply toothed on the margins. Each leaf has 3 main veins that show prominently on the underside. The roots are fibrous, coarse, and shallow. 

 

Snakeroot with Flowers

In late summer, numerous small heads of minute white flowers appear at the top of the stem and the ends of the branches. These flower heads, except that they are white, are almost exactly like the flower heads of the familiar ageratum of gardens. Later the flowers are replaced in the heads by small black seeds each with a crown of soft white hairs.

Because the leaves of white snakeroot resemble those of the nettle, other plants with nettle-like leaves are often mistaken for it. Two such plants are the nettle-leaved sage and the nettle-leaved vervain. Even without flowers or fruit, these plants can be easily distinguished from white snakeroot. The nettle-leaved sage, a rare plant in some southern Illinois counties, has square stems; white snakeroot stems are round. The nettle-leaved vervain, a common weed throughout Illinois, has lance-shaped leaves; white snakeroot leaves are broad at the base but narrow quickly in a wedge-shaped part to the petiole.

Distribution

White snakeroot is found in woods of all types and along streams in wooded pastures throughout the Midwest. It persists after woods are cut, and often may be found many years after the land has been cleared, although usually in such areas it occurs only as scattered unthrifty plants. In prairie regions, it is not often found except in the woods bordering streams.

Conditions of Poisoning

An animal may die from eating either a large amount of white snakeroot at one time or small amounts over a long period. The eating of small quantities more or less continuously gives rise to the animal disease known as trembles. It is also the cause of the well-known and much-feared milk sickness of man -- a disease that is contracted from drinking milk or eating milk products from poisoned cows. Milk sickness claimed thousands of lives in the early 1800s, with perhaps the most well-known victim being Abraham Lincoln's mother. Nursing calves and lambs may die from mothers' milk that is contaminated with snakeroot even though the mother animals show no signs of poisoning. Cattle, horses, and sheep are the animals most often poisoned. 

Control

During the dry period of late summer, animals should not be pastured in woods or fields where there is white snakeroot. If the pasture is known to be infested, animals should be moved out of it within the first few days of July and should not be returned to it until the following year.

Eradication of white snakeroot is not easy. Chemical weed-killers cannot be used satisfactorily, because they endanger trees and other plants of the pasture. The best way to reduce the number of the plants is to pull them out by the roots and burn them; the best time to do this is in September, when the plants are more easily identified by their white blossoms. If the plants are pulled after a hard rain while the ground is soft, the shallow roots come out readily.

Toxic Principle
  • The apparent toxic principle in white snakeroot has been given the trivial name tremetol. It has been described as a fat-soluble, high molecular weight alcohol.
  • Crude tremetol, was later shown to be separable into a toxic ketone fraction (61%) (tested in goldfish) and a nontoxic sterol fraction (39%). The ketone fraction was later separated into tremetone, dihydrotremetone, and hydroxytremetone. These may all be components of a fragile tremetol molecule.
Clinical Signs

White snakeroot can endanger the lives of persons and animals other than those that have actually eaten the plant. Consumption of the plant may also affect the flavor and odor of the milk produced by the poisoned animal.

In Cattle and Sheep: 

Although animals that have fed on white snakeroot may be listless and somewhat inactive at first, the first noticeable manifestations of poisoning are loss of weight and trembling following exercise. Trembling is especially marked in the muzzle and legs. As poisoning progresses, cattle lose appetite, become constipated, lose weight, and gradually become weaker until they are not able to stand. Additional signs may include a peculiar odor to the breath and urine, excessive salivation, and quickened, difficult breathing. Later, complete relaxation without tremors and coma are seen, with death following in 2-10 days.

The clinical signs that are exhibited by poisoned sheep are similar to those shown by cattle. Death may occur in a few days or may be delayed.

In cases of chronic poisoning, post-mortem examination generally reveals extensive degenerative changes in the liver and kidney.

In Horses:

The onset of clinical signs in white snakeroot poisoned horses is within 2 days to 3 weeks after initial ingestion (usually after at least several days of ingestion). The major effects are related to congestive heart failure. Tremors are inconsistently observed in horses with white snakeroot poisoning. Horses may stand with legs wide apart. Sweating may be evident especially between rear legs, and stumbling in the rear legs may be noted when horses are turned. Severe depression, bloody urine, and/or choking may also occur. Sometimes swelling is present in the lower neck area, near the thoracic inlet. They may exhibit a jugular pulse and a rapid heart rate. Changes in electrocardiogram include increased heart rate, ST elevation, and variable QRS complexes, and ventricular premature beats. Cardiac arrhythmias are often present.

In Guinea Pigs:

The refusal to eat by the animal is the first sign, followed by listlessness and crouching with half-closed eyes. The hair becomes rough. Muscular tremors may not be noticeable, but complete lack of muscular coordination and stupor precede death. (White snakeroot poisoning, by R. Graham and V.M. Michael. Circular #436, University of Illinois College of Agriculture,1935.)

Animals Affected

Cattle, sheep, horses, guinea pigs

References Used

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

Euphorbia milii (Crown of Thorns)

Description

A low-growing evergreen shrub with very thorny grooved stems and branches. The stems are purplish brown and are 1-2 feet tall on average, but can reach 3 feet in a warm climate. The thorns are sharp, pointed and are 1/2 inch long on avarage. The ovate leaves are 1-3 inches long, few in number, and are found mostly at the growing ends. The cyathia, a type of inflorescence characteristic of the genus Euphorbia, are born in small umbels and have showy, ovate and bright red bracts. The small flowers are produced in clusters of 2-8 at the tips of green flower stem about 1 inch long. Genus Euphorbia includes other commonly available plants such as poinsettia (E. pulcherrima) and snow-on-the-mountain (E. marginata).

Distribution

A native of Madagascar, Crown of Thorns is widely grown as a house plant in northern states including Illinois, and as a common garden plant in southern states, especially Florida.

Conditions of Poisoning

The poisonous principle is present in all parts of the plant. Euphorbia species generally are highly unpalatable, but animals may eat them due to lack of good forage. Drying does not destroy the toxicity of the plant, and Euphorbia in hay may be slightly more palatable to livestock. Contact with the white, milky sap may cause severe blistering as well as intense pain to open cuts or eyes. Honey made from the flowers of these plants may be toxic.

Control

Light infestations of pastures usually are not a problem since most Euphorbia can be grazed to a limited degree without noticeable reactions. Mowing and reseeding with hardy pasture plants is helpful for heavier infestations of Euphorbia, since most pasture species are annuals; light restocking rates also may help increase the predominance of desirable forage species. Supplemental feeding is suggested in some areas when desirable forage is scarce.

Toxic Principle

The poisonous principles have been identified as phorbol esters. Phorbol esters activate protein kinase C. Protein phosphorylation is increased by protein kinase C which may alter multiple enzyme and other protein functions. Effects may result in cytoskeletal damage and tumor promotion.

Clinical Signs

Generally horses, cattle, sheep, cats, dogs and humans are affected by Euphorbia and may experience severe irritation of the mouth and gastrointestinal tract, sometimes with hemorrhage and diarrhea. Other general signs include blistering, swelling about the eyes and mouth, excessive salivation and emesis, abdominal pain and weakness. The sap may cause dermatitis. Death is rare. Work horses may suffer severe blisters and loss of hair on the ankles. Approximately 3 kg of E. prostrata and E. marginata when fed to cattle produces severe scours and emaciation.

Animals Affected

Horses, cattle, sheep, cats, dogs

G

Glechoma hederacea L. (Ground Ivy)

Description

Ground ivy is a low, prostrate perennial herb with slender 4-sided stems that hug the ground, root at their joints, and often cover areas of many square feet. Its leaves, two at a joint, are raised on slender stalks. They are roundish and have scallop-like teeth on their margins. Its small bluish flowers, found in the axils of the leaves, appear from April to May and even into July.

Distribution

Ground ivy, sometimes called Creeping Charlie, is a common weed of moist shaded places and is to be found in fence rows, about farmsteads, and in woodland pastures, gardens, and wastelands. It is also frequent near streams and ditches. A native of Europe, it has become a common plant throughout Illinois. 

Conditions of Poisoning

Ground-ivy poisoning is rare, probably because most animals do not like the bitter taste of the plant. Horses, the animals usually affected, are poisoned only after eating large quantities of the plant, either green or dried in hay.

Control

Reasonable care should be taken not to graze animals in areas that are heavily infested with ground ivy, particularly at times when other herbage is dry or scarce. Neither should hay be made in meadows where the plant is abundant. Ground ivy should be regarded as a weed and destroyed in all places where it is a danger to animals. It is easily destroyed by cultivation.

Toxic Principle

Like other members of the mint family, ground ivy contains a volatile, aromatic oil. It also contains a bitter substance of unknown chemical constitution. It is collected as a drug plant and is used medicinally in small amounts as a stimulant and tonic. 

Clinical Signs

After having eaten large amounts of ground ivy, poisoned animals, especially horses, slobber and sweat, and the pupils of their eyes become dilated. They pant for breath as if from overstimulation. Such poisoning is rarely fatal.

Animals Affected

Horses

Gymnocladus dioica (L.) Koch (Kentucky Coffee Tree)

Description

Kentucky coffee tree is a large round-barked tree belonging to the legume family and reaches heights of 60 to 100 feet. Its short trunk, 1 to 2 feet in diameter, divides into several large branches that end in contorted, stout twigs. Twice-compound leaves are arranged feather-fashion in 3-7 pairs of leaflets which are more or less ovalish without marginal teeth and 2-4 inches long. The tree is most easily identified in fall and winter for its large depressed leaf scars. The leaf which emerges late in spring is made up of a hundred or more separate oval leaflets arranged on the branches of the rib.

The flower, which blooms in May, is inconspicuous, greenish-white in terminal racemes, and has a tubular base about 1/2 inch long. Male and female flowers are found on the same tree. The fruit is a thick, flat pod, containing 4-7 flat broad seeds with a sticky pulp between them. The pulp dries at maturity and the seeds become olive-brown, 1/2 - 3/4 inches in diameter. 

Distribution

The Kentucky coffee tree grows in moist woods, creek banks, and flood plains. It is mainly found in the Midwest from western Ohio to eastern Kansas and Oklahoma, southern Michigan to northern Alabama and Tennessee. The tree was much planted around farm houses and may now be maintained as ornamentals around newer buildings.

Conditions of Poisoning

The leaves, seeds and pulp are poisonous and have affected sheep, cattle, horses, and humans. Sprouts eaten in the spring have produced toxicosis. Pods and seeds on the ground eaten in the fall or winter have produced poisoning. Leaves, young sprouts and seeds with the gelatinous material around them contain the toxin. 

Control

Until spring grasses and herbage are abundant, animals should not be grazed in woods where the Kentucky coffee tree grows or where it has been cut and allowed to sprout. Since there are never more than a few of these trees in any woodland, sprouts can be grubbed out periodically, and thus poisoning from them can be prevented.

The pods cling to the tree through the winter and are shed in the spring. To prevent animals from eating the fallen pods, large fruiting trees can be fenced in. Although the tree has little commercial value, it is so rare that unnecessary cutting of it is not recommended.

Toxic Principle

The toxic principle of this plant is uncertain. It is possibly the quinolizidine alkaloid, cytisine, which acts like nicotine.

Clinical Signs

Clinical signs include rapid onset (within 1 hour) of intense gastrointestinal irritation, profuse diarrhea and straining, vomiting, hypertension, bradycardia, respiratory depression, muscle paralysis, and convulsions. Animals often display depression. Death usually occurs within a day after clinical signs appear.

Animals Affected

Sheep, horses, cattle