Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.

University Library, University of Illinois at Urbana-Champaign

Plants Toxic to Animals

A

Acer rubrum (Red Maple)

Description

Trees are large and can reach heights of approximately 100 feet when mature. Leaves have three to five lobes and are simple and opposite with red petiole, shiny green topside and white/gray underside. Leaves turn red during the fall. 

Distribution

Red maple trees are common throughout most of eastern North America and south to Florida and Texas. They adapt to moist or dry areas and are often planted as ornamental trees.

Conditions of Poisoning

Poisoning usually occurs when horses consume wilted or dried leaves of the red maple. Most poisonings occur in the fall when the bulk of the leaves drop. 

Control

Maintain a good feeding program for horses and remove red maple leaves and fallen branches from horse enclosures. Do not plant red maple trees in or near horse enclosures.

Toxic Principle

Pyrogallol.

Clinical Signs

Consumption of the wilted leaves is known to cause oxidative damage to equine erythrocytes that may result in intravascular or extravascular hemolysis, Heinz body formation, and/or methemoglobinemia. After consumption, horses exhibit clinical signs within 1 to 2 days. Symptoms include destruction of red blood cells (anemia), weakness, dark urine, difficulty breathing, abortion, and death. The fatality rate after consumption has been reported to be between 50-65%.

Animals Affected

Horses, alpacas, zebras

References Used

Wilson, D. A., DVM. (2012). Clinical veterinary advisor: The horse. St. Louis, MO: Elsevier Saunders.

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

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

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

Aesculus glabra Willd. (Buckeye, Horse Chestnut)

Description

A tree which reaches a maximum height of 50-70 feet with a rough bark that has disagreeable odor. The leaves are made up of 5 rather large, leaf-like leaflets set like the fingers or a hand, at the end of the leafstalk.

Blossoms: Large clusters of pale yellowish-green blossoms appear at the ends of the branches. They are usually seen in May after the leaves appear.

Fruit: A globular, spine-roughened capsule which contains 1-3 large glossy chocolate-colored nuts each with a large whitish scar. 

Distribution

The buckeye grows in woods throughout Illinois, preferring rich, moist soils. In the northern part of the state it is infrequent. Southward it is more common, but nowhere in Illinois does it occur other than as an occasional tree. 

Conditions of Poisoning

Sprouts, leaves, and nuts of the plant are reported to have caused illness or death in cattle, sheep, and pigs when these animals were pastured where sprouts were present and where other forage was scarce. Especially poisonous are the young sprouts and the seeds. Poisoning does not always follow when animals feed on the tree. In experimental feeding, symptoms of poisoning appeared in only a small number of the animals.

Control

Until grass or other forage is abundant, animals should not be allowed to graze in woodland pastures where there are buckeye sprouts. Sprouts and seedlings should be grubbed out of pastures. If the trees are few, as they usually are, it may be advisable to collect the nuts in order to keep hogs from getting them. The tree has little commercial value, but since it is uncommon, it should not be unnecessarily destroyed. 

Toxic Principle

Glycosides, especially a glycosidic saponin called aesculin and possibly a narcotic alkaloid. Note: Glycoside is defined as a molecule containing a carbohydrate (sugar) moiety, particularly any such natural product in plants.

Clinical Signs

In simple stomached animals, vomiting and gastroenteritis are the primary effects of the toxic glycoside.

Animals Affected

Cattle, sheep, pigs, goats

References Used

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

Allium spp. (Wild Onion)

Description

Wild onion (A. validum or A. canadense) is a bulbous herb of the Amaryllis family and is a close relative of cultivated onion (Allium cepa L.). It has a distinct onion odor. It has slender grass-like leaves and reaches about 2 feet in height when flowers appear in late summer. Leaves are narrow, long, and with parallel edges arising from the small underground bulb. Flowers, varying in color, depending on the species,  from white to pink, appear at the top of a leafless stem and eventually become bulblets which drop to the ground and propagate. 

It is thought that the name Chicago is derived from the smell of wild onions:

"Indians, mainly Potawatomi, who were the most powerful tribe around the south end of Lake Michigan, hunted, traded furs, and occasionally camped in the area they called "Checagou," evidently referring to the garlic wild onion smell which permeated the air." -- Encyclopedia of Illinois, 2nd. Edition. Somerset Publishers, New York, 1994. p. 138.

Distribution

Wild onion is found in meadows and woodlands in the northeastern and north central United States. Other species grow throughout the western United States. Several species of wild onion are found in Illinois with Allium canadense found in all counties. 

Conditions of Poisoning

Cattle are susceptible to onion poisoning and eating large amounts of this plant can cause death in this species. In areas where culled onions are grown commercially, they can be fed to cattle with few problems when the feed is mixed with ample amounts of other feed components. Poisoning may occur when cool spring weather delays growth of grass and wild onions are available in comparatively large amounts for cattle to graze. Horses and sheep are less susceptible, with goats being the least susceptible. In some cases, sheep may eat onions and show nothing more than slight hemoglobinemia. 

Control

Due to its easily-separable bulbs and thin, waxy leaves, wild onion can be difficult to remove both by hand pulling and through the use of herbicides. Using a trowel to dig up the entire bulb and roots can be effective and can help reduce the number of bulb and bulblets left in the ground. Steps to remove the plants should be taken during late fall in November and again in late winter/early spring before new plants are produced in March.

Toxic Principle

Both wild and cultivated onions contain the same toxic principle, N-propyl disulfide which primarily affects erythrocytes. The principle effects are related to hemolysis (rupture of red blood cells). This is believed to be secondary to oxidant-associated effects, and Heinz bodies may sometimes be evident in red blood cells. Other compounds are believed to be responsible for the lacrimator (tear producing) and antithrombotic (anti-clotting) effects associated with onions and garlic. Various sulfur-containing metabolites are probably responsible for the odors associated with ingestion of onions and garlic.

Clinical Signs

Urine discoloration may vary from wine red to almost black. Muscle weakness, rapid breathing, and a rapid heart rate may be noted if hemolysis is sufficiently severe. Some animals may be icteric (jaundiced) and/or have a characteristic onion odor to the breath. Loss of weight and appetite may also occur. Although severe toxicoses may be lethal, doses may cause only taste and odor problems in the milk of dairy cows.

Animals Affected

Cattle, cats, dogs, horses, sheep, goats

References Used

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

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

https://lee.ces.ncsu.edu/2015/02/wild-onionwild-garlic-kill-control-prevent-it-2/

Amaranthus retroflexus L. (Pigweed)

Other common names: Carelessweed, Redroot, Red-rooted pigweed
Description

Pigweed is a stout, rapidly growing annual plant that can reach 3-4 feet tall. The stems are branched and hairy, and can be red to purple in color. The leaves of the plant are alternate, petiolate, ovate to lanceolate, and pointed at the apex. The flowers are light green and grow in dense spikes or panicles approximately 3-8 inches long. The taproot of redroot pigweed is bright red in color, and seeds are black and shiny.

Distribution

A variety of pigweed species grow throughout North America, with redroot pigweed (Amaranthus retroflexus) being the most common and typical of the genus. It can be found in cultivated and disturbed soils along roadsides and waste areas, and is also common in and around animal enclosures. Prostrate pigweed (A. blitoides), tumble pigweed (A. albus), and Palmer amaranth (A. palmeri) are also frequently seen and have similar characteristics to the redroot pigweed.

Conditions of Poisoning

Poisoning occurs when the plant is ingested. Pigs and cattle should not be allowed to graze in areas where pigweed is present, and plants should be removed if seen growing in or near animal enclosures.

Control

The plant spreads and grows quickly from wind-blown seeds, so effort should be taken to remove the plants from the desired areas before flowering and the areas should remain under close observation if mature plants are seen in the vicinity.

Toxic Principle

Significant quantities of oxalates and nitrates may accumulate in the plant over time, and other currently unknown toxic substances may also be present.

Clinical Signs

Swelling of and around the kidneys can be caused by oxalates in the plant, if present. Renal tubular nephrosis can occur and has most likely been the cause of death of affected animals in previous cases, and it has been seen even in cases where oxalates were not present implying that there is an unknown compound in the plant that is the cause. Nitrate poisoning can occur if the plant has accumulated nitrates over its lifetime.

Animals Affected 

Pigs, cattle

References Used

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

Apocynum cannabinum L. and other species (Dogbanes)

Description

This is a perennial milky-juiced herb of the Dogbane family. It has opposite leaves which are simple, nearly 5 inches long and about half as wide, with smooth margins.

Distribution

This weed is scattered throughout the United States in open fields, pastures, along roadsides and streams. Sometimes the plant is cultivated for ornament and for use in medicine.

Conditions of Poisoning

This plant is reportedly very distasteful and animals usually avoid it, so poisoning is infrequent. It is consumed primarily when other forage is in short supply. Both green and dried dogbane are toxic. Fifteen to thirty grams of green leaves has been reported as causing death of a horse or a cow. The root of Apocynum cannabinum has been employed therapeutically to "retard the heart in systole" and was therefore used for "dropsy" and "heart trouble."

Control

Keep animals from grazing along roadsides, in abandoned fields, or in any other areas where dogbanes are growing. Do not cut hay from land infested with dogbanes. Get rid of these plants in all areas in which animals are grazed or from which hay is cut to be used as feed.

Toxic Principle

Cardiac glycosides.

Clinical Signs

Animals that have eaten appreciable quantities of dogbane show first a rise in body temperature, sweating, and a strong pulse but cold extremities. The pupils of the eyes are usually dilated. The inside of the mouth and nostrils becomes discolored, and later the mouth becomes so sore that the animal refuses food. In spite of this, bowel action may be frequent. Death is likely to follow.

Animals Affected

Horses, cattle, sheep, cats, dogs, goats

Arisaema spp. (Jack-in-the-Pulpit)

Emerging Jack-in-the-Pulpit

Description 

Jack-in-the-pulpit is a stemless plant, 8 inches to 2 feet tall, that grows in the woods. It has one or two long-stalked, 3-parted leaves; and at the tip of its flowerstalk, which is not quite as long as the leaves, it has a peculiar flowering structure, tinted shades of green, greenish-white, and purple.

The leaves and flower stalks rise from an underground, perennial corm, hard and turnip-shaped. The fruit is a mass of brilliant red or scarlet berries, each containing 1 to 5 seeds. 

Mature Fruit

Distribution

Jack-in-the-pulpit is common to abundant throughout Illinois in open and dense, moist woods and may be seen also in woods clearings and occasionally in pastures and at the edges of pastures that were formerly woodland. Though commonly regarded as an early spring plant, it persists through the growing season and is conspicuous in late summer and fall by its dense clusters of red berries. 

Conditions of Poisoning

Animals, if grazed in wooded pastures in early spring when other forage is not available, may eat the root of this plant. Susceptible species are cattle, sheep, goats, and swine. 

Control

Cattle should not be grazed in wooded pastures at any time when jack-in-the-pulpit is one of the few green plants available. Although there is no satisfactory way of eradicating it, its numbers will be considerably lessened if it is consistently dug when seen. 

Toxic Principle

The corms of the plant contain an unidentified volatile acrid principle, calcium oxalate crystals, and possibly an alkaloid. The corms are gathered, dried, and sold by drug collectors. 

Clinical Signs

Cattle, sheep, goats, and swine are susceptible to this poisoning, but they seldom eat enough of the plant to cause trouble. The corms would doubtless affect any animal that ate them. Eating the corms causes an intense burning and biting sensation in the mouth, throat, and stomach; large doses may cause inflammation of the stomach and intestine. Affected animals show evidence of colic, and they attempt to cool the mouth and throat with water. 

Animals Affected

Cattle, sheep, goats, swine

Asclepias syriaca L. (Milkweed, Common)

Description

Common milkweed is an herbaceous perennial that can grow from 2 to 6 feet tall, though typically only grows to 3-4 feet. The stems of the plant are stout and leaves are light green, simple, and oblong, and are alternate and opposite. Stems and leaves produce a milky juice when injured. Flowers are dusty pink or lavender and fragrant, and grow in domed, drooping umbels in the leaf axis. Seed pods are 2 to 4 inches long and have a warty appearance, and split open when ripe to release numerous silky-tailed seeds which are dispersed by the wind.

Distribution

Common milkweed can be found in all parts of the central to eastern United States. The plant can be found in fields, open woods, and by roadsides and railroad tracks.

Conditions of Poisoning

All parts of the plant are poisonous when eaten and toxicity is retained when dried.

Control

Milkweeds tend to grow singly or in small groups and can be controlled by digging out individual plants or selectively spraying an herbicide such as 2,4-dichlorophenoxyacetic acid (2,4-D). Care should be taken not to include milkweed when making hay, as toxicity is not reduced by drying.

Toxic Principle

Cardiac glycosides and resinoids. The cardiac glycosides affect myocardial conduction and contractility in the poisoned animal.

Clinical Signs

Signs of poisoning usually begin within 8-10 hours after ingestion and severity is influenced by how much of the plant was consumed. Symptoms include vomiting, stupor, weakness, spasms, and rapid and/or weak pulse.

Animals Affected

Milkweed species are known to affect sheep, goats, cattle, horses, domestic fowl, cats, and dogs

References Used

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

https://plants.ces.ncsu.edu/plants/all/asclepias-syriaca/

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=b480

C

Cannabis sativa (Hemp)

Description

Hemp is a rough, odorous herb with few or no branches and angular stems that are covered in short, stiff hairs. Resources differ regarding the size of the plant, but the reported range can be from 3-12 feet tall. Lower leaves are opposite and upper leaves are alternate, and the leaves are long-stalked and palmately divided into 3-7 toothed leaflets. Flowers are small and green.

Distribution

Hemp can be found in most areas of the United States, particularly where it was originally grown for its fiber. Habitats include borders of floodplain woodlands, borders of low-lying fields, weedy meadows along rivers, fence rows, and roadside ditches.

Conditions of Poisoning

Poisoning commonly occurs when large quantities of the plant are ingested. All parts of the plant are poisonous, but the greatest toxicity is found in the flower stalks. Poisoning symptoms can also occur from inhalation of the plant.

Control

Mammalian herbivores avoid browsing hemp when other plants are available, so be sure that animals grazing in areas infested with hemp have plentiful options for food.

Toxic Principle

Resins, including Delta-9-THC (tetrahydrocannabinol) and cannabidiol.

Clinical Signs

Prolonged depression, vomiting, incoordination, sleepiness or excitation, hypersalivaton, dilated pupils, blurred vision, low blood pressure, low body temperature, seizure, coma, death (rare). Consumption of the plant may also affect the flavor and odor of the milk produced by the poisoned animal.

Animals Affected

Dogs, cats, horses

References Used

https://plants.ces.ncsu.edu/plants/all/cannabis-sativa/

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/indian-hemp-0

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

Chenopodium album L. (Lamb's Quarters or Lambsquarters)

Description

Lamb's Quarters is an annual weed with branched stems. The stems have purple or red stripes or marks. The leaves alternate and are green with a grey underside. The leaves growing at the base of the stem have more of a serrated edge than the leaves towards the top of the plant do. The leaves at the top of the plant are smaller. Flowers grow at the end of the stems and are grey-green. 

Distribution

Lamb's Quarters is found throughout North America.

Conditions of Poisoning

Animals are poisoned when they consume large quantities of Lamb's Quarters. The leaves and grains of the plant used as a food source in some areas, and can be safely consumed in limited doses.

Toxic Principle

Lamb's Quarters is a Nitrate Accumulator. It can acquire toxic levels of nitrates if grown in rich soil or if it's fertilized like it would be if grown in cropland. It can also accumulate toxic levels of Oxalates and Sulfates. All parts of the plant are toxic. 

Clinical Signs

Signs of nitrate poisoning include difficulty breathing and the mucous membranes of the mouth and vulva turning brown due to methemoglobin in the blood. Other symptoms are depression, weakness, tremors, weak pulse, and coma. Sudden death can occur due to respiratory failure because of methemoglobin forming. 

Animals Affected

Cattle, sheep, goats

References Used

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

Cicuta maculata L. (Water Hemlock)

Description

This 2-10 feet tall herbaceous perennial or biennial native of the Umbelliferae family is very difficult to separate from other species of the same family. It has a tuberous root with 2-8 oblong tubers which are 1.5-3 inches long and about 1/2 inch thick at the thickest point near the middle and stem end. The purple-streaked stems are stout and erect with much branching. The stems are solid when very young, but become hollow with nodes where the leaflets are attached. The stems are chambered with horizontal diaphragm of pith tissue which are more closely arranged at the base of the stem. The horizontal plates of piths are most easily visible by cutting the stem base lengthwise.

The alternate leaves are pinnately 2-3 times compound. The leaves of most species are lanceolate, 2-5 inches long, and sharply toothed. The base of the long petioles clasp the stem.

Flowers are white and tiny (no more than 1/8 inch across), have 5 petals, and appear in loose compound umbels at branch ends in mid summer. Umbels measure from 2 to 8 inches across and become somewhat spherical in fruit. Fruits are ovoid and ribbed on the outer surface.

New growth begins from tubers as well as from seeds. 

Distribution

The water hemlock occurs throughout the state of Illinois. It is occasionally encountered in wet pastures and meadows and frequently in and along ditches, in the low ground near streams, in low woods, and around ponds and lakes. 

Conditions of Poisoning

Water hemlock is among the most poisonous plants in Illinois. Although the leaves and fruit, either green or dried in hay, can be eaten without danger, a relatively small amount of the tuber will kill a cow in a short time. There is little danger during summer and fall as stock are not likely to browse on the tall coarse plants. But in early spring, the livestock will eat the young leaves and stems sprouting from the ground, and in doing so may pull the shallow tubers out of the soft wet ground and eat them also. 

Control

In the early spring livestock should not be allowed to graze in meadows infested with water hemlock, for the young shoots are then springing up and animals can easily pull the poisonous tubers from the wet, soft ground.

Pastures should be free of this plant. It is easiest to remove plants in the early spring. If the plant is not to be removed, it can be kept from spreading by mowing the tops before the seeds form. If extensive marshy areas become infested, it may be necessary to drain the land and cultivate it for several years before animals can again be safely pastured there. 

Toxic Principle

The toxic principle of water hemlock has been called cicutoxin and is a resinoid. It is a thick, yellow liquid with a carrot-like or raw parsnip-like odor. It is concentrated especially in the roots and the base of the stem at or below ground surface. The roots are toxic all year. Young leaves are nearly as toxic as roots, but mature leaves have been consumed in summer and autumn without associated problems.

Ingestion of two ounces of water hemlock tubers can kill a sheep, and eight to ten ounces of mature plant can kill a cow.

Clinical Signs

The clinical signs of water hemlock poisoning often follow a rather definite sequence. Frothing at the mouth may occur first, but this is quickly followed by uneasiness, frenzied movements, and other evidence of intense abdominal pain. Jerking of the muscles, twisting backward of the head and neck (opisthotonus), together with stiffening of the limbs, dilated pupils, and rolling eyeballs are followed by spasms of the diaphragm (in some species this may be associated with vomiting), convulsions, and death. The poison acts so quickly that the affected animal may die 15 minutes after the first abnormalities are noticed. 

Animals Affected 

Cattle, sheep

Claviceps purpurea (Fr.) Tul. (Ergot)

Description

Ergot is a fungus that lives as a parasite in the blossoms of grasses. When the grass heads are nearly mature, it appears as jumbo grains protruding from the heads. Ergot grains, which are fungus bodies and not seeds, are several to many times the size of the grass seed. They are dark violet to almost black and are curved, hard, and hornlike. Ergot varies in abundance from year to year.

Distribution

Ergot is well known as a disease of rye. It also attacks many of the wild grasses that grow along roads, in fence rows, woods, meadows, and pastures, and can often be found on wild rye, quack grass, red top, and bromegrass. It occurs throughout Illinois, being more abundant in some years than in others. 

Conditions of Poisoning

Animals get ergot either in the grain fed them or by grazing on infected grass. Obtained in either way, ergot may cause acute poisoning if a large quantity is eaten at one time. Also, because the effect of ergot is cumulative, poisoning may develop slowly if lesser quantities are eaten regularly. Experiments have shown, however, that a small amount of ergot is not injurious to dairy cattle that are amply provided with a balanced ration.

Control

Do not feed grain or hay that contains ergot. Clean contaminated grain before feeding it. Destroy infested hay. Before planting rye, clean the seed thoroughly either by mechanical means or by immersing it in a 25% salt solution. If using the salt solution, skim off ergots as they rise to the top; then wash the rye seed in water to remove the salt; dry, and plant. If wild grasses are infested, burn them to destroy the ergot.

Besides attacking many kinds of wild grasses, ergot is frequently abundant on rye in rye-fields and on volunteer rye in wheat-fields. Grain from these fields (or screenings used as feed) is very likely to cause poisoning. If there is much ergot in the grain, its effect can be very severe.

Toxic Principle

The toxic action of ergot is due to the numerous alkaloids (ergotamine, ergocristine, ergonovine, etc.) present in the sclerotia and other components--choline, ACH, histamine, sterols. Over 40 alkaloids have been identified which are derivatives of lysergic acid, some of which are inactive.

The important naturally occurring alkaloids are ergotamine and ergonovine. Of these, ergonovine is more readily absorbed. Both compounds are potent smooth muscle activators. LSD is also derived from ergot, and the smooth muscle contracting activity, although sometimes present, is not always seen. LSD causes depersonalization or hallucinations and may produce toxic psychosis.

Clinical Signs

Ergot poisoning, often called ergotism, produces two distinct types of clinical signs. Acute poisoning, which results from eating a large amount of ergot at one time, causes muscular trembling, discoordination, convulsions, and painful contraction of the muscles. In fatal cases the animal becomes delirious.

The gangrenous type of poisoning, which follows continued feeding on smaller amounts of ergot, causes the animal to become dull and depressed and to develop gangrene of the tail, feet, ears, or teats. Gangrene may vary from rather simple sores around the coronary band or top of the hoof, in the space between the claws, or on the teats to a loosening of the hoof or the sloughing of a larger part of a limb or of the tail, ears, or teats. Before sloughing occurs, a well-marked line of division can be seen between the healthy and gangrenous tissue, similar to the type of lesion that has been observed in selenium poisoning in such western states as Kansas, Nebraska, and Wyoming.

Nausea, vomiting, colic, and diarrhea may occur in both types of poisoning. Even when none of the above signs of ergotism are apparent, the presence of ergot in feed should be suspected whenever pregnant animals have an otherwise inexplicable tendency to abort.

Animals Affected

All animals and humans are susceptible to ergotism, but cattle are often the most affected.

References Used

https://beef.unl.edu/cattleproduction/ergot-poisoning-in-cattle

Conium maculatum L. (Poison Hemlock)

Description

Poison hemlock is a coarse biennial herb with a smooth, purple-spotted, hollow stem and leaves like parsley. It grows 3 to 6 feet tall and in late summer has many small white flowers in showy umbels. Its leaves are extremely nauseating when tasted.

Although sometimes confused with water hemlock, poison hemlock can be distinguished by its leaves and its roots. The leaf veins of the poison hemlock run to the tips of the teeth; those of the water hemlock run to the notches between the teeth. The poison hemlock root is long, white, and fleshy. It is usually unbranched and can be easily distinguished from the root of water hemlock, which is made up of several tubers. 

Distribution

Poison hemlock was introduced into North America from Europe, where it is native. It has become well established in all regions except desert. The plants are easily found along roadsides, on the banks of streams, ditches, and canals, and as a weed in fields. It is found in all parts of Illinois. 

Conditions of Poisoning

Animals allowed to graze pastures infested with this plant are most likely to be poisoned in early spring, when tender and succulent new leaves come from the root. Similar regrowth takes place in the early autumn. The root itself seems to be nearly harmless in spring, but later in the year all parts - roots, stem, leaves, and fruit - become extremely poisonous. It was the juice of poison hemlock with which the ancient Greeks killed Socrates. Many cases of human poisoning occur because the hemlock roots are mistaken for parsnips; the leaves, for parsley; and the roots and seeds, for anise. 

Control

Poison hemlock should be dug up and completely destroyed because it is dangerous to both animals and humans.

Toxic Principle

Piperidine (nicotinic) alkaloids in Conium include coniceine, coniine, N-methyl coniine, conhydrine, and pseudoconhydrine. The alkaloid content is variable with the stage of development and the stage of reproduction of the plant. During the first year of growth, the plant alkaloid content tends to be low. Plants in the second year, however, have alkaloid contents of approximately 1% in all plant parts. The alkaloid content is somewhat higher after sunny weather, as compared to rainy weather. The highest concentration of alkaloids occur in the seeds which can contaminate cereal grains. Coniine (2-propylpiperidine) and N-methyl coniine progressively increase in flowers and fruits, while coniceine decreases during plant maturation. In the vegetative stage - i.e. early growth - coniceine (W'-2 propylpiperidine) is the predominant alkaloid. Coniceine and coniine are the primary teratogenic alkaloids of Conium.

Clinical Signs

Susceptible species include cattle, pigs, elk, poultry, goats, sheep, and rabbits to some extent. Toxicosis has been experimentally reproduced in sheep and horses as well. Consumption of the plant may also affect the flavor and odor of the milk produced by the poisoned animal.

Systemic effects: After having eaten poison hemlock, animals may lose their appetites, salivate excessively, bloat, and have a rapid but feeble pulse. They also show evidence of muscular incoordination and appear to have great abdominal pain. Other signs include muscle tremors, frequent urination and defecation, recumbency, mydriasis, and "nervousness" followed by severe depression. In animals that die, breathing ceases due to respiratory paralysis before cardiac arrest. Convulsions, which occur in water-hemlock poisoning, do not follow the eating of poison hemlock.

Teratogenic effects: Birth defects due to ingesting poison hemlock occur in (at least) calves and piglets and may include crooked legs (crooked calf disease, arthrogryposis), cleft palate, and kinked tails. Arthrogrypotic skeletal malformations occur in calves when poison hemlock is ingested by pregnant cows between days 40 through 70 of gestation. Similar skeletal lesions occur in pigs between days 40 through 61 of gestation. Cleft palates can occur in piglets if pregnant swine ingest poison hemlock between days 30 through 45 of gestation.

Animals Affected

Humans, cattle, birds, sheep, goats, pigs, horses, dogs, cats

References Used

Vetter, J.  "Poison hemlock (Conium maculatum L.)." Food and Chemical Toxicology. 42 (2004):1373-1382. 

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

Convallaria majalis (Lily of the Valley)

Description

Lily of the Valley is perennial that originally grew in Europe. The leaves are oval or oblong shaped and dull green in color. The plant has an arched stem with typically 5-18 white, bell-shaped flowers growing on it. Lily of the Valley does occasionally grow small, red berries. It is a popular potted house plant.

Distribution

While it is native to Europe, Lily of the Valley has been introduced in North America and has now become naturalized in some parts.

Conditions of Poisoning

Lily of the Valley is poisonous when eaten, though it's more common for children to get poisoned than for animals. There have been few reports of animals getting poisoned from consuming Lily of the Valley. 

Toxic Principle

There are 38 different cardenolides which have been identified in Lily of the Valley, with a large concentration of them found in the plant's roots. All parts of the plant, including the bulb and roots, are toxic. 

Clinical Signs

Vomiting, salivation, limited diarrhea, irregular pulse or decreased heart rate, seizures.

Animals Affected

All animals, people

References Used

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