Deadly Plants

Dogs love to play, and they can easily get bored and chew on things or dig up things that they shouldnt. This is a normal activity for dogs, but sometimes the substances they discover and ingest can be dangerous or deadly. Protect your dog from poisonous plants by keeping them out of his reach.

Castor Bean, Castor Oil Plant

Toxicity Rating: Extremely high. Death is likely if your dog consumes even small amount of castor bean, although unbroken seeds may pass with no harm done.

Dangerous Parts: The seeds are the primary source of toxin, but the rest of the plant may also be slightly toxic.

Symptoms: Stomach irritations, diarrhea, abdominal pain, increased heart rate, profuse sweating, collapse, convulsions and death.

Plant Description: This robust shrublike plant with reddish to purple stems may reach 12 feet in height. A perennial in the tropics, it is grown as a garden annual and the beans are processed commercially for oil. It originated in Africa and grows best in warm climates. In the northern United States, it is not unusual to see castor beans planted in public parks. The large (4 to 30 inches across), umbrellalike leaves have five to nine pointed, fingerlike lobes. Long purple leaf stems grow near the centers of the leaf blades. Greenish-white or reddish-brown flowers appear in narrow, upright clusters. The fruit is a three-lobed, green or red capsule with a soft, spiny exterior. One large, mottled seed develops in each lobe. The shiny black-and-brown seeds look like large ticks.

The seed is only toxic if the outer shell is broken or chewed open, which dogs can do. Seeds swallowed intact usually pass without incident. Signs of toxicity may not manifest for 18 to 24 hours after ingestion. Dogs first show signs of depression and a mild increase in temperature. Later, gastrointestinal signs predominate -- including vomiting and diarrhea (which may be bloody), colic and abdominal pain. An affected dog may go into convulsions, collapse and die. Death generally occurs within 36 hours of consumption as a result of severe gastrointestinal irritation, anaphylaxis and shock. The toxin in castor bean is closely related to the toxin in rosary pea.

First Aid: If you see your dog eating castor bean, call a veterinarian immediately. If you discover consumption several hours later, a veterinarian will be able to provide supportive care and treatment for shock, but death may still result.

Prevention: Do not allow pets access to this plant. Do not allow seeds or any other part of the plant to be incorporated into your dogs food. Do not let castor beans grow where the dog can get at them. To decrease the chances of intoxication, snip off the flower heads before they develop into seeds; this will protect children as well as pets.


Water Hemlock

Toxicity Rating: High. This is one of the most toxic plants in the United States.

Dangerous Parts: The roots contain the highest concentration of toxin, but all parts are toxic. A dog may drink from tainted water or eat the roots.

Symptoms: Nervousness, respiratory difficulties, muscle tremors, collapse, convulsions (seizures) and death, which may be sudden.

Plant Description: One or more species of water hemlock can be found in wet fields and swampy ground all over the United States and Canada. The perennial stem of water hemlock may grow to 7 feet in height from its cluster of two to eight fleshy or tuberous roots. Stems are smooth, branching, swollen at the base, purple-striped or mottled, and hollow except for partitions at the junction of the root and stem. A yellow, oily liquid smelling like parsnip exudes from cut stems and roots.

Leaves alternately resemble a feather and are toothed, with the leaf veins extending to the leaf notches. Leaf petioles (leafstalk) partially sheath the stems. The small, white flowers are borne in flat-topped, umbrellalike clusters at the tips of stems and branches. Seed pods are small and dry with rounded, prominent ribs. Water hemlock grows in swampy areas and marshes, wet meadows and pastures and along stream banks and low roadsides.

Signs: Water hemlock is one of the most toxic plants in the United States. A very small amount can cause death. Humans have died after only one or two bites of what they thought were parsnips (water hemlock root resembles a parsnip). The roots are toxic at all times, even when dry. Dogs have been poisoned by drinking water that had been contaminated with trampled water hemlock roots.

The toxin is cicutoxin, a yellow gummy substance with a carrotlike odor. Cicutoxin affects the central nervous system. The dose needed to cause clinical signs and the lethal dose are nearly the same, a little more than 1 gram of water hemlock per kilogram of body weight; 8 ounces (approximately 230 grams) will kill a horse.

Once the dog has ingested even a small amount of the plant, signs will develop within an hour, possibly as soon as 10 to 15 minutes. The syndrome is typically very violent. Stimulation of the central nervous system begins with nervousness and dilated pupils. Later, muscle tremors occur, and consequently, the animal has respiratory difficulty, falls down, and goes into convulsions. Death, from respiratory paralysis and terminal convulsions, is a typical outcome, occurring within 30 minutes of the onset of signs. If a sublethal dose is consumed and the animal survives for 4 to 6 hours, he may recover, but may suffer from temporary or permanent damage to heart or skeletal muscle.

First Aid: If you see your dog eating water hemlock, especially the roots, get him away from the plant and call a veterinarian immediately. Emergency measures may be tried, but death may still occur. Seizures cause severe damage to the heart and skeletal muscle, and this damage can be avoided if the seizures are controlled. However, this is rarely possible under farm and field conditions because the toxin acts so quickly.

Prevention: Prevent access to areas where water hemlock grows or completely remove the plant (most importantly the roots) before letting animals into the area, especially in the spring or when the roots may be exposed due to plowing, ditch maintenance or other similar activity.


Poison Hemlock

Toxicity Ratings: Moderate to high.

Dangerous Parts of the Plant: All parts, especially young leaves and seeds.

Symptoms: Nervousness, trembling, loss of coordination, depression, coma and death.

Plant Description: This biennial herb came to the United States and Canada from Europe and grows as a weed. It can reach 3 to 8 feet in height and has a smooth, purple-spotted stem and triangular, finely divided leaves with bases that sheathe the stem. Fresh leaves and roots have a rank, disagreeable odor that is reminiscent of parsnips. Small but attractive white flowers, arranged in umbrellalike clusters open in early summer. The fruit is tiny, flattened and ridged. Underground is a fleshy, unbranched white taproot. There are no hairs on the stems or leaves of poison hemlock and no branching, feathery bracts beneath the flower clusters. These plants are commonly found along roadsides, edges of cultivated fields, railroad tracks, irrigation ditches and stream banks and in waste areas.

Signs: Affected dogs manifest signs within 2 hours of eating the plant, tend to become nervous, and will tremble and become uncoordinated. After the excitement phase, the animal becomes depressed. The heart and respiratory rates slow down, the legs, ears and other extremities become cold, and bloating may occur. Even at this stage, the animal may not die, but may remain like this for several hours to days, then recover.

In lethal cases, the animals tend to die within 5 to 10 hours after the onset of clinical signs, typically from respiratory failure, in which case the mucus membranes will appear blue. Affected animals are reported to give off a mousy odor.

Spring is the primary season for poison hemlock, possibly because the plant is more palatable then. Toxicity increases throughout the growing season, and the roots become toxic only later in the year. Once dried, toxicity is reduced but not eliminated.

First Aid: If your dog eats poison hemlock, call a veterinarian immediately. Treatment consists of eliminating the toxin from the gastrointestinal tract and providing supportive care. If the dog becomes comatose but does not die, he will require intense nursing care until he recovers.

Prevention: Even small amounts are lethal to dogs. It is best to keep all dogs away from areas that have poison hemlock. Also note that poison hemlock may be difficult to eradicate.



Toxicity Rating: Extremely high.

Dangerous Parts: The seeds and seedlings contain the highest quantity of toxin, but the whole plant can be considered toxic. The seed burs can cause mechanical damage, especially to dogs.

Symptoms: Gastrointestinal irritation, weakness, respiratory difficulty, behavioral changes, cardiac abnormalities and death.

Plant Description: The angled, sometimes red- or black-spotted stems of cocklebur grow 1 to 3 feet high. Leaves of this many-branched annual are alternate, hairy, rough-textured (like sandpaper), somewhat heart-shaped, toothed and lobed. Flowers are inconspicuous with male flowers in terminal spikes and female flowers in clusters in the leaf axils. The fruit is a hard, oval, prickly bur about inch long, containing two seeds. Because seeds germinate best after being soaked in water, the plants usually grow along the shores of ponds where water has receded. The edges of farm ponds may be lush with young cockleburs. Seedlings have small strap-shaped leaves inch wide by 1 inches long. They also pop up in gardens, fields, roadsides and other areas of nearly full sunlight. Cocklebur is a common weed that grows in all parts of the United States.

Signs: Liver damage may result from ingesting cocklebur, and death is likely if a dog consumes a sufficient dose (ingestion of green plant at approximately 0.75% of body weight). The bur can cause mechanical damage. Embedded seed heads can cause local irritation and infections or can become more deeply embedded in tissues and migrate into the body. Irritation and infection often develop, necessitating removal of the plant matter.

Signs depend on location of the bur and can include head shaking; sneezing; discharge from the nose or eyes; rubbing at the ears, eyes, or mouth; difficulty in chewing or swallowing; or signs of digestive disturbance. Toxic signs are most commonly seen from seedlings in late spring and early summer and from burs later in the summer. As the cocklebur plant matures, the toxicity decreases, except for the seeds. The seedlings are extremely dangerous and typically sprout in wet areas, such as along streams, at the edges of ponds, and in receding floodplains. Some animals recover, but this may take weeks.

First Aid: If a dog is observed eating cocklebur, contact a veterinarian immediately. In the meantime, prevent further consumption of the plant by all animals. Keep the dog quiet until the veterinarian arrives.

Prevention: Yard or pasture management is essential to prevent cocklebur poisonings. Mature, seed-bearing plants should be removed to prevent seeding and germination. If removal of the plants is impractical, fence off areas where seedlings are likely to germinate.


Jimsonweed, Thorn Apple, Datura

Toxicity Rating: Extremely high. The plant and seeds are extremely toxic. This plant is abused as a hallucinogen by humans, and deaths in humans and animals have been reported.

Dangerous Parts: All parts, especially seeds.

Symptoms: Dilated pupils, agitation, trembling and delirium. The victim may appear to be experiencing hallucinations and suffer from convulsions (which may be violent), coma and death.

Plant Description: This coarse annual grows to a height of 5 feet and has strongly scented, coarsely toothed, green or purplish alternate leaves. The large trumpet-shaped flowers are white or purplish and are formed singly at the forks in the stems. The fruits are hard, spiny capsules that split open along four lines at maturity to release numerous tiny black seeds. Jimsonweed commonly grows in cultivated fields, waste areas, barnyards, abandoned pastures, roadsides and feedlots. Several different species are found across North America.

Signs: Dogs will avoid eating jimsonweed whenever possible. The plants may become palatable after the application of herbicides, thus greatly increasing the risk of toxicosis.

Once the plant is consumed, signs may become apparent within a few minutes and up to several hours later. The alkaloids in jimsonweed act on the central nervous system as well as the autonomic nervous system that controls bodily functions. Animals may seek water to drink, have dilated pupils (especially if a seed is lodged in the eye), become agitated, exhibit increased heart rate, tremble, become delirious, appear to be experiencing hallucinations, have convulsions (which may be violent), become comatose, and possibly die. Consumption of jimsonweed during gestation may result in abortions or birth defects.

As much as 0.7% of the fresh weight of the leaves may be made up of toxic alkaloids. The seeds are the greatest risk, with alkaloid concentrations believed to be greater than the leaves and stems. Even the nectar is toxic.

First Aid: Prevent further exposure to the plant. To avoid human injury, exercise caution when working with an affected dog. Contact a veterinarian if signs are severe, since there are medications that can counteract the effects of the toxin. Also, if consumption was recent, contact a veterinarian quickly because it may be possible to evacuate a large amount of the plant from the digestive tract before the toxicosis becomes severe. For less severely affected animals (a veterinarian will be able to assist in determining the degree of intoxication), the clinical signs will resolve within a day or two, so keep the dog quiet and undisturbed.

Prevention: If the plants are treated with herbicides, make sure they are completely dead before dogs are allowed into the area. Use caution, especially near the edges of fields where jimsonweed is likely to grow.


Cherry (All Types)

Toxicity Rating: Extremely high.

Dangerous Parts: Damaged leaves pose the greatest risk. All parts are potentially toxic.

Symptoms: Anxiety, respiratory problems, staggering, convulsions, collapse and death, which may be sudden.

Plant Description: Cherries may grow as a tree or shrub, commonly in fencerows, roadside thickets and open woods.

Signs: Black cherry contains cyanogenic precursors that release cyanide whenever its leaves are damaged by frost, trampling, drought, wilting or being blown down from the tree during storms. Most dogs can consume small amounts of healthy leaves, bark and fruit safely, but when hungry dogs consume large amounts of fresh leaves or small amounts of damaged leaves (as little as 2 ounces), clinical cases of poisoning will occur, and many dogs may die. When dogs are confined or bored, the chance for ingestion of toxic levels increase.

Cyanide poisoning prevents the body from using oxygen at the cellular level, so although the dogs physically can breathe, their tissues and cells suffocate. After consumption, signs will usually manifest within a few minutes, but sometimes up to an hour may pass. The dogs will try to breathe more rapidly and deeply, then become anxious and stressed. Later, trembling, incoordination, attempts to urinate and defecate, and collapse may occur, which can proceed to a violent death from respiratory or cardiac arrest within a few minutes to an hour. If an affected dog is still alive 2 or 3 hours after consumption, chances are good that he will live.

First Aid: The clinical signs of cyanide poisoning tend to come on rapidly, and dogs may be found dead without much warning. If your dog exhibits toxic signs, call a veterinarian immediately. There is an antidote, but it needs to be given intravenously and within a few minutes of the onset of signs, and it is often impossible to get help in time. Do not handle or stress affected dogs any more than absolutely necessary, since this will worsen the signs. Also, affected dogs are extremely stressed and may be dangerous to work with, so exercise caution to avoid human injury.

Prevention: Do not house or confine dogs near cherry trees, since boredom increases the likelihood that the plant will be eaten. For most species of cherry, the fruit is safe for consumption. It is the leaves and bark that pose the greatest risk.



Toxicity Rating: Extremely toxic, death is likely.

Plant Description: Several species of yew are planted as ornamental shrubs or hedges. They are woody perennials with flat, to1 inch long, evergreen leaves that are lighter green on the underside and broader than pine needles. The berry, technically called an aril, is grape-sized, juicy and bright scarlet. It has a hole in the end, which makes it look cuplike. Dark evergreen needles make yew a beautiful plant in all seasons of the year.

Symptoms: Sudden death is the typical sign. Occasionally respiratory problems, trembling, weakness, heart problems and stomach upset occur.

Signs: "Found dead" is the typical presenting sign. Very rarely dogs will show signs up to 2 days later: trembling, slow heart rate, respiratory difficulty, stomach upset and diarrhea. Yew is exceptionally toxic, with one mouthful able to kill a horse or cow within 5 minutes. Dogs may be poisoned accidentally when yew trimmings are thrown into the yard or when yew is planted as an ornamental within their reach. There are infrequent reports of stomach upset, diarrhea, seizures and aggressive behavior occurring after dogs chew the leaves.

First Aid: First aid is usually impractical, since the dog will die so quickly if he has consumed a toxic dose. Prevent other animals from being exposed and use caution around dogs showing clinical signs to prevent human injury. If a dog is still alive, contact a veterinarian. Cardiac drug therapy may be attempted, but success is unlikely.

Prevention: Never allow yew plants or trimmings within reach of any dog likely to eat plants. Dogs, however, rarely chew on yew, so unless your dog is prone to chewing on plants, it is not necessary to remove yew from ornamental plantings. Toxicities in dogs often occur when puppies are confined to a pen with yew and chew the plant out of boredom. The fleshy red berry is not considered toxic, but consumption is not advised.



Toxicity Rating: High. Ingestion of even small amounts can kill.

Dangerous Parts: The entire plant is toxic. Consuming leaves, fresh or dried, will poison most dogs.

Symptoms: Gastrointestinal irritation, cardiac abnormalities and death, which may be sudden.

Plant Description: Oleander grows as an indoor plant in the northern United States and as an outdoor shrub in California, Florida and other warm regions. The leaves are lance-shaped, thick and leathery, and grow opposite each other. Sometimes leaves may grow in whorls. The leaves are 8 to 10 inches long, although smaller specimens will have shorter leaves. Flowers are showy, approximately 1 to 3 inches in diameter, and grow in large clusters at the ends of the branches. They can be white or any shade of pink or red.

Signs: Oleander contains the toxins oleandrin and nerioside, which are very similar to the toxins in foxglove (digitalis). Oleander is not palatable, but may still be eaten by hungry dogs. Dried or wilted leaves may be slightly more palatable than fresh leaves, but the leaves are toxic when wilted or dried. In one report, approximately pound of leaves (about 30 or 40 leaves) delivered a lethal dose to an adult horse.

Clinical signs may develop rapidly, and the dog may be found dead with no prior warning. In other cases, depression coupled with gastrointestinal distress is evident: vomiting, diarrhea (which may be bloody), and abdominal pain. Irregularities in the heart rate and rhythm will occur: the heart may speed up or slow down and beat erratically. As the toxicosis progresses, the extremities may become cold, and the mucous membranes pale. Trembling and collapse can occur, followed by coma and death within a few hours.

First Aid: If dogs are observed eating oleander, contact a veterinarian immediately. The toxin acts quickly and is lethal in small amounts. Emergency measures may be used to empty the gastrointestinal tract of remaining plant matter, and medications may be administered to control the effects that the toxin has on the heart. Despite emergency care, the dog may still die, but the sooner treatment is begun, the better the chance for survival.

Prevention: Be able to identify oleander and exercise extreme caution when pets (and humans) are in the vicinity of these plants. Never place oleander where your dogs can have contact. Take extra care in cases where leaves can fall into a yard or a pen occupied by a bored or hungry dog. Animals and humans can also be hurt by oleander, even without touching the plant. Breathing the smoke or burning branches can cause poisoning, and merely smelling the flowers may be harmful.


Rosary Pea

Toxicity Rating: High. Even one bean can kill.

Dangerous Parts: The beans are the primary risk.

Symptoms: Severe gastrointestinal irritation, vomiting, abdominal pain, collapse and death.

Plant Description: This twisting perennial vine grows naturally in tropical climates. Rosary pea is established in certain areas of southern Florida. Leaves are alternate and compound, with 8 to 15 leaflets. Flowers are small and can be any shade, from white to red to purple. The seed pod is about 1 inches long, containing several seeds that are bright red with a black spot.

Signs: Toxic signs resulting from rosary pea ingestion are very similar to those caused by castor bean, except that the rosary pea toxin is more powerful. One seed, if well-chewed, can kill an adult human. The toxins in rosary pea are a protein called abrin and a glycoside called abric acid, which cause severe gastrointestinal signs. This progresses to weakness, shock and death within a short time.

Seeds are used to make jewelry and rosaries. If the seed is swallowed without damage to the seed coat, poisoning is unlikely, and the seed will tend to pass without incident. In cases where the seed coat is chewed or opened (as in drilling to make jewelry), toxic signs and death are likely.

First Aid: If your dog ingests rosary pea, contact a veterinarian immediately. Prevent further exposure, and get other animals away from the source. Emergency measures may be used to eliminate the toxin from the stomach and intestines. Once gastrointestinal signs appear, it may be inadvisable to evacuate the stomach and intestines for fear of doing even greater damage, but a veterinarian will decide this. Care is primarily symptomatic and supportive of the digestive upset, weakness and shock. Affected dogs are likely to die even with care.

Prevention: Rosary pea should never be allowed in the home for the safety of dogs and humans alike. If jewelry or rosaries are made of rosary pea, discard them immediately.



Toxicity Rating: Extremely high. One mushroom can be fatal.

Dangerous Parts: The whole mushroom is poisonous.

Symptoms: Mushrooms can be poisonous in many different ways. Members of the gyromitra family, such as the false morel, contain a substance that may cause vomiting, abdominal pain and bloody diarrhea. More serious signs include seizures, coma and death.

Other mushrooms, such as the psilocybe species, contain a hallucinogen.

Most poisonous mushrooms are members of the amanita family, which are responsible for most of the mushroom-related deaths that occur in dogs each year. These mushrooms contain a substance that causes liver damage. They are so poisonous that one amanita mushroom cap can kill a dog. Tragically, these mushrooms do not produce symptoms until many hours after they are eaten. By that time, treatment is usually of little value. If the mushrooms are spoiled, there may be preliminary signs of illness.

Plant Description: Few individuals have the special training needed to identify mushrooms accurately. For this reason, it is often best to assume an unknown mushroom is poisonous and empty the dogs stomach.

Signs: Phallotoxins and amatoxins are the toxins responsible for fatalities in mushroom poisonings. When first ingested, mushrooms may actually taste quite good to your dog. The toxins, however, enter the bloodstream and within 2 to 5 hours, the phallotoxins are converted by liver enzymes into a compound that attacks liver cells. Only when it no longer helps to pump the stomach does the animal begin to suffer extreme pain. Dogs experience pain and muscle cramps, often in the limbs, as well as vomiting, lethargy and distorted vision.

Several days later, the slower acting, more toxic, amatoxins begin to take effect. During the interim the victim may feel somewhat better. The onset of severe pain then continues from 4 to 6 days and often culminates in death. Even when death does not occur, the illness lasts several weeks and may do permanent liver damage.

Other Mushroom Toxins:

Muscarine is a toxin that excites the parasympathetic nervous system, which results in the slowing of the heart, dilation of blood vessels, and constricting of the pupils of the eyes. Atropine has been used to counteract the effect of muscarine in poisonings. Once the dog recovers, there are no long-term effects.

Muscimol, ibotenic acid, pantherin, tricholomic acid, and related compounds are hallucinogenic substances that act on the central nervous system. They, and not the muscarine, constitute the psychoactive toxins in Amanita muscaria. When a large amount of Amanita muscaria containing these toxins is ingested, it often results in severe illness but dogs usually recover.

Psilocybin and psilocina are well-known compounds in the LSD family of hallucinogenic compounds (lysergic acid). They have a strong hallucinogenic effect on the central nervous system, producing visions, smothering sensations and optical distortions. Perhaps the most important factor is the presence of other toxic compounds in addition to the hallucinogenic agent. Species are common throughout the world and occur wherever cattle and horses are raised.

Monomethylhydrazine not only causes blood poisoning, but also affects the central nervous system. Symptoms include diarrhea, vomiting and incooordination.

First Aid: After your dog eats a mushroom, treatment must be started as soon as possible to make sure the animal does well. Contact your veterinarian as soon as possible. If a dog is already exhibiting symptoms, it may be necessary to bring him to the veterinarian for treatment. The poison center can assist your veterinarian by suggesting appropriate treatment.

Prevention: Because mushrooms can literally appear overnight, inspect your yard for mushrooms before allowing your pet outside, and be wary of mushrooms when in public places such as parks and woods.