List of poisonous plants
Plants cannot move to escape their predators, so they must have other means of protecting themselves from herbivorous animals. Some plants have physical defenses such as thorns, spines and prickles, but by far the most common type of protection is chemical. Over millennia, through the process of natural selection, plants have evolved the means to produce a vast and complicated array of chemical compounds in order to deter herbivores. Tannin, for example, is a defensive compound that emerged relatively early in the evolutionary history of plants, while more complex molecules such as polyacetylenes are found in younger groups of plants such as the Asterales. Many of the known plant defense compounds primarily defend against consumption by insects, though other animals, including humans, that consume such plants may also experience negative effects, ranging from mild discomfort to death.
Many of these poisonous compounds also have important medicinal benefits. The varieties of phytochemical defenses in plants are so numerous that many questions about them remain unanswered, including:
- Which plants have which types of defense?
- Which herbivores, specifically, are the plants defended against?
- What chemical structures and mechanisms of toxicity are involved in the compounds that provide defense?
- What are the potential medical uses of these compounds?
These questions and others constitute an active area of research in modern botany, with important implications for understanding plant evolution and for medical science.
Below is an extensive, if incomplete, list of plants containing poisonous parts that pose a serious risk of illness, injury, or death to humans or animals. There is significant overlap between plants considered poisonous and those with psychotropic properties, some of which are toxic enough to present serious health risks at recreational doses. It is also important to remember that there is a distinction between plants that are poisonous because they naturally produce dangerous phytochemicals, and those that may become dangerous for other reasons, including but not limited to infection by bacterial, viral, or fungal parasites, the uptake of toxic compounds through contaminated soil or groundwater, and/or the ordinary processes of decay after the plant has died; this list deals exclusively with the former. Many plants, such as peanuts, also produce compounds that are only dangerous to people who have developed an allergic reaction to them, and with a few exceptions, those plants are not included on this list (see list of allergens instead). Human fatalities caused by poisonous plants – especially resulting from accidental ingestion – are rare in the United States.
Poisonous food plants
Many plants commonly used as food possess toxic parts, are toxic unless processed, or are toxic at certain stages of their lives. Some only pose a serious threat to certain animals (such as cats, dogs, or livestock) or certain types of people (such as infants, the elderly, or individuals with pathological vulnerabilities). Most of these food plants are safe for the average adult to eat in modest quantities. Notable examples include:
- Apple (Malus domestica). Seeds are mildly poisonous, containing a small amount of amygdalin, a cyanogenic glycoside. The quantity contained is usually not enough to be dangerous to humans, but it is possible to ingest enough seeds to provide a fatal dose.
- Cassava (Manihot esculenta). Roots and leaves contain two cyanogenic glycosides, linamarin and lotaustralin. These are decomposed by linamarase, a naturally occurring enzyme in cassava, liberating hydrogen cyanide . Cassava varieties are often categorized as either sweet or bitter, respectively signifying the absence or presence of toxic levels of cyanogenic glycosides. The 'sweet' cultivars can produce as little as 20 milligrams of cyanide per kilogram of fresh roots, whereas bitter ones may produce more than 50 times as much (1 g/kg). Cassavas grown during drought are especially high in these toxins. A dose of 40 mg of pure cassava cyanogenic glycoside is sufficient to kill a cow. It can also cause severe calcific pancreatitis in humans, leading to chronic pancreatitis. Processing (soaking, cooking, fermentation, etc.) of cassava root is necessary to remove the toxins and avoid getting sick. In the tropics, where cassava farming is a major industry, "Chronic, low-level cyanide exposure is associated with the development of goiter and with tropical ataxic neuropathy, a nerve-damaging disorder that renders a person unsteady and uncoordinated. Severe cyanide poisoning, particularly during famines, is associated with outbreaks of a debilitating, irreversible paralytic disorder called konzo and, in some cases, death. The incidence of konzo and tropical ataxic neuropathy can be as high as 3 percent in some areas." For some smaller-rooted sweet varieties, cooking is sufficient to eliminate all toxicity. The cyanide is carried away in the processing water and the amounts produced in domestic consumption are too small to have environmental impact. The larger-rooted, bitter varieties used for production of flour or starch must be processed to remove the cyanogenic glycosides. Industrial production of cassava flour, even at the cottage level, may generate enough cyanide and cyanogenic glycosides in the effluvia to have a severe environmental impact.
- Cherry (Prunus cerasus), as well as other Prunus species such as peach (Prunus persica), plum (Prunus domestica), almond (Prunus dulcis), and apricot (Prunus armeniaca). Leaves and seeds contain amygdalin, a cyanogenic glycoside.
- Grape (Vitis spp.). Potentially toxic to dogs, although the precise mechanism is not fully understood. See grape and raisin toxicity in dogs.
- Indian pea (Lathyrus sativus). A legume grown in Asia and East Africa as an insurance crop for use during famines. Like other grain legumes, L. sativus produces a high-protein seed. The seeds contain variable amounts of β-N-Oxalyl-L-α,β-diaminopropionic acid or ODAP, a neurotoxic amino acid. ODAP causes wasting and paralysis if eaten over a long period, and is considered the cause of the disease neurolathyrism, a neurodegenerative disease that causes paralysis of the lower body and emaciation of gluteal muscle (buttocks). The disease has been seen to occur after famines in Europe (France, Spain, Germany), North Africa and South Asia, and is still prevalent in Eritrea, Ethiopia and parts of Afghanistan when Lathyrus seed is the exclusive or main source of nutrients for extended periods.
- Kidney bean or common bean (Phaseolus vulgaris). The toxic compound phytohaemagglutinin, a lectin, is present in many varieties of common bean but is especially concentrated in red kidney beans. The lectin has a number of effects on cell metabolism; it induces mitosis, and affects the cell membrane in regard to transport and permeability to proteins. It agglutinates most mammalian red blood cell types. Consumption of as few as four or five raw kidney beans may be sufficient to trigger symptoms, which include nausea, vomiting, and diarrhea. Onset is from 1 to 3 hours after consumption of improperly prepared beans, and symptoms typically resolve within a few hours. Phytohaemagglutinin can be deactivated by cooking beans at 100 °C (212 °F) for ten minutes, which is required to degrade the toxin and is much shorter than the hours required to fully cook the beans themselves. For dry beans the U.S. Food and Drug Administration (FDA) also recommends an initial soak of at least 5 hours in water, after which the soaking water should be discarded. However, lower cooking temperatures may have the paradoxical effect of potentiating the toxic effect of haemagglutinin. Beans cooked at 80 °C (176 °F) are reported to be up to five times as toxic as raw beans. Outbreaks of poisoning have been associated with the use of slow cookers, the low cooking temperatures of which may be unable to degrade the toxin.
- Lima bean or butter bean (Phaseolus lunatus). Raw beans contain dangerous amounts of linamarin, a cyanogenic glycoside.
- Lupin. Some varieties have edible seeds. Sweet lupines have less and bitter lupines more of the toxic alkaloids lupinine and sparteine.
- Lemon, as well as lime, orange and other citrus fruits are known to contain aromatic oils and compounds of Psoralen which is toxic to dogs, cats, and some animals. The acid is found all over the entire plant. Symptoms include vomiting, diarrhea, depression and photosensitivity.
- Mango tree. Mango peel and sap contain urushiol, the allergen in poison ivy and poison sumac that can cause urushiol-induced contact dermatitis in susceptible people. Cross-reactions between mango contact allergens and urushiol have been observed. Those with a history of poison ivy or poison oak contact dermatitis may be most at risk for such an allergic reaction. Urushiol is also present in mango leaves and stems. During mango's primary ripening season, it is the most common source of plant dermatitis in Hawaii.
- Nutmeg (Myristica fragrans). Contains myristicin, a naturally occurring insecticide and acaricide with possible neurotoxic effects on neuroblastoma cells. It has psychoactive properties at doses much higher than used in cooking. Raw nutmeg produces anticholinergic-like symptoms, attributed to myristicin and elemicin. The intoxicating effects of myristicin can lead to a physical state somewhere between waking and dreaming; euphoria is reported and nausea is often experienced. Users also report bloodshot eyes and memory disturbances. Myristicin is also known to induce hallucinogenic effects, such as visual distortions. Nutmeg intoxication has an extremely long delay before peak is reached, sometimes taking up to seven hours, and effects can be felt for 24 hours, with lingering effects lasting up to 72 hours.
- Onions and garlic. Many members of the Allium genus contain thiosulphate, which in high doses is toxic to dogs, cats and some types of livestock. Cats are more sensitive to Allium.
- Potato (Solanum tuberosum). Potatoes contain toxic compounds known as glycoalkaloids, of which the most prevalent are solanine and chaconine. Solanine is also found in other members of the Solanaceae plant family, which includes Atropa belladonna ("deadly nightshade") and Hyoscyamus niger ("henbane") (see entries below). The concentration of glycoalkaloid in wild potatoes is sufficient to produce toxic effects in humans. The toxin affects the nervous system, causing headaches, diarrhea and intense digestive disturbances, cramps, weakness and confusion, and in severe cases coma and death. Poisoning from cultivated potatoes occurs very rarely, however, as toxic compounds in the potato plant are generally concentrated in the green portions of the plant and in the fruits, and cultivated varieties contain smaller concentrations than wild plants. Cooking at high temperatures (over 170 °C or 340 °F) also partly destroys the toxin. However, exposure to light, physical damage, and age can increase glycoalkaloid content within the tuber, the highest concentrations occurring just underneath the skin. Tubers that are exposed to light turn green from chlorophyll synthesis, thus giving a visual clue as to areas of the tuber that may have become more toxic; however, this does not provide a definitive guide, as greening and glycoalkaloid accumulation can occur independently of each other. Some varieties of potato contain greater glycoalkaloid concentrations than others; breeders developing new varieties test for this, and sometimes have to discard an otherwise promising cultivar. Breeders try to keep solanine levels below 200 mg/kg (200 ppmw). However, when these commercial varieties turn green, even they can approach concentrations of solanine of 1000 mg/kg (1000 ppmw). The U.S. National Toxicology Program suggests that the average American consume no more than 12.5 mg/day of solanine from potatoes (the toxic dose is actually several times this, depending on body weight).
- Rhubarb (Rheum rhaponticum). The leaf stalks (petioles) are edible, but the leaves themselves contain notable quantities of oxalic acid, which is a nephrotoxic and corrosive acid present in many plants. Symptoms of poisoning include kidney disorders, convulsions and coma, though it is rarely fatal. The LD50 (median lethal dose) for pure oxalic acid in rats is about 375 mg/kg body weight, or about 25 grams for a 65 kg (~140 lb) human. Although the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%, so almost 5 kg of the extremely sour leaves would have to be consumed to reach the LD50. Cooking the leaves with soda can make them more poisonous by producing soluble oxalates. However, the leaves are believed to also contain an additional, unidentified toxin, which might be an anthraquinone glycoside (also known as senna glycosides). In the edible leaf stalks, the concentration of oxalic acid is much lower, contributing only about 2–2.5% of the total acidity, which is dominated by malic acid. This means that even the raw stalks may not be hazardous (though they are generally thought to be in the US). However, the tart taste of the raw stalks is so strong as to be unpalatable to most consumers.
- Tomato (Solanum lycopersicum). Like many other members of the nightshade family (Solanaceae), tomato leaves and stems contain solanine that is toxic if ingested, causing digestive upset and nervous excitement. Use of tomato leaves as an herbal tea (infusion) has been responsible for at least one death. Leaves, stems, and green unripe fruit of the tomato plant also contain small amounts of the poisonous alkaloid tomatine, although levels are generally too small to be dangerous. Ripe tomatoes do not contain any detectable tomatine. Tomato plants can be toxic to dogs if they eat large amounts of the fruit, or chew plant material.
Other poisonous plants
Countless other plants not commonly used as food are also poisonous, and care should be taken to avoid accidentally contacting or ingesting them:
- Abrus precatorius (known commonly as jequirity, crab's eye, rosary pea, 'John Crow' bead, precatory bean, Indian licorice, akar saga, giddee giddee, jumbie bead, ruti, and weather plant). The attractive seeds (usually about the size of a ladybug, glossy red with one black dot) contain abrin, a ribosome-inactivating protein related to ricin, and very potent. Symptoms of poisoning include nausea, vomiting, convulsions, liver failure, and death, usually after several days. Ingesting a single seed can kill an adult human. The seeds have been used as beads in jewelry, which is dangerous; inhaled dust is toxic and pinpricks can be fatal. The seeds are unfortunately attractive to children.
- Aconitum genus (several species, commonly called aconite, wolfsbane and monkshood). All parts are poisonous. The poison is an alkaloid called aconitine, which disables nerves, lowers blood pressure, and can stop the heart. Even casual skin contact should be avoided; symptoms include numbness, tingling, and cardiac irregularity. It has been used as poison for bullets (by German forces during World War II), as a bait and arrow poison (ancient Greece), and to poison water supplies (reports from ancient Asia). If ingested, it usually causes burning, tingling, and numbness in the mouth, followed by vomiting and nervous excitement. It is usually a quick-acting poison, and has been used in the past for killing wolves (hence one of the common names).
- Actaea pachypoda (also known as doll's eyes or white baneberry). All parts are poisonous, especially the berries, the consumption of which has a sedative effect on cardiac muscle tissue and can cause cardiac arrest.
- Adenium obesum (also known as sabi star, kudu or desert-rose). The plant exudes a highly toxic sap which is used by the Meridian High and Hadza in Tanzania to coat arrow-tips for hunting.
- Aesculus hippocastanum (commonly known as horse-chestnut). All parts of the plant are poisonous, causing nausea, muscle twitches, and sometimes paralysis.
- Agave genus. The juice of a number of species causes acute contact dermatitis, with blistering lasting several weeks and recurring itching for several years thereafter.
- Ageratina altissima (commonly known as white snakeroot). All parts are poisonous, causing nausea and vomiting. Often fatal. Milk from cattle that have eaten white snakeroot can sicken, or kill, humans (milk sickness).
- Agrostemma githago (commonly known as corn cockle). Contains the saponins githagin and agrostemmic acid. All parts of the plant are reported to be poisonous and may produce chronic or acute, potentially fatal poisoning, although it has been used in folk medicine to treat a range of ills, from parasites to cancer. There are no known recent clinical studies of corn cockle which provide a basis for dosage recommendations, however doses higher than 3 g (of seeds) are considered toxic.
- Aquilegia genus (several species commonly known as columbine). Seeds and roots contain cardiogenic toxins which cause both severe gastroenteritis and heart palpitations if consumed. The flowers of various species were consumed in moderation by Native Americans as a condiment with other fresh greens, and are reported to be very sweet, and safe if consumed in small quantities. Native Americans also used very small amounts of the root as an effective treatment for ulcers. However, medical use of this plant is difficult due to its high toxicity; columbine poisonings are easily fatal.
- Areca catechu (commonly known as betel nut palm and pinyang). The nut contains an alkaloid related to nicotine which is addictive. It produces a mild high, some stimulation, and lots of red saliva, which cannot be swallowed as it causes nausea. Withdrawal causes headache and sweats. Use is correlated with mouth cancer, and to a lesser extent asthma and heart disease.
- Arum maculatum (commonly known as cuckoo-pint, lords and ladies, jack-in-the-pulpit, wake robin, wild arum, devils and angels, cows and bulls, Adam and Eve, bobbins and starch-root). All parts of the plant can produce allergic reactions. The bright red berries contain oxalates of saponins and can cause skin, mouth and throat irritation, resulting in swelling, burning pain, breathing difficulties and stomach upset. One of the most common causes of plant poisoning.
- Asparagus genus (several species including Asparagus officinalis and Asparagus densiflorus). Though asparagus plants cultivated for food are typically harvested before they reach reproductive maturity, the berries of the mature plant are poisonous, containing furostanol and spirostanol saponins. Rapid ingestion of more than five to seven ripe berries can induce abdominal pain and vomiting. Sulfur compounds in the young shoots are also considered at least partially responsible for mild skin reactions in some people who handle the plant.
- Atropa belladonna (commonly known as deadly nightshade, belladonna, devil's cherry and dwale, an Anglo-Saxon term meaning "stupifying drink"). One of the most toxic plants found in the Western hemisphere, all parts of the plant contain tropane alkaloids - as do those of its equally deadly sister species A.baetica, A.pallidiflora and A.acuminata. The active agents are atropine, hyoscine (scopolamine), and hyoscyamine, which have anticholinergic properties. The symptoms of poisoning include dilated pupils, sensitivity to light, blurred vision, tachycardia, loss of balance, staggering, headache, rash, flushing, dry mouth and throat, slurred speech, urinary retention, constipation, confusion, hallucinations, delirium, and convulsions. The root of the plant is generally the most toxic part, though this can vary from one specimen to another. Ingestion of a single leaf of the plant can be fatal to an adult. Casual contact with the leaves can cause skin pustules. The berries pose the greatest danger to children because they look attractive and have a somewhat sweet taste. The consumption of two to five berries by children and ten to twenty berries by adults can be lethal. In 2009, a case of A. belladonna being mistaken for blueberries, with six berries ingested by an adult woman, was documented to result in severe anticholinergic syndrome. The plant's deadly symptoms are caused by atropine's disruption of the parasympathetic nervous system's ability to regulate involuntary activities such as sweating, breathing, and heart rate. The antidote for atropine poisoning is physostigmine or pilocarpine. A. belladonna is also toxic to many domestic animals, causing narcosis and paralysis. However, cattle and rabbits eat the plant seemingly without any harmful effects. In humans its anticholinergic properties will cause the disruption of cognitive capacities like memory and learning.
- Brugmansia genus (commonly known as angel's trumpet). All parts of all plants in this genus contain the tropane alkaloids scopolamine and atropine; often fatal. These plants are closely related to and were once grouped with members of the Datura genus, which contain the same deadly alkaloids.
- Caladium genus (commonly known as angel wings, elephant ear and heart of Jesus). All parts of all plants in this genus are poisonous. Symptoms are generally irritation, pain, and swelling of tissues. If the mouth or tongue swell, breathing may be fatally blocked.
- Cerbera odollam (commonly known as the suicide tree). The seeds contain cerberin, a potent toxin related to digoxin. The poison blocks the calcium ion channels in heart muscle, causing disruption of the heart beat. This is typically fatal and can result from ingesting a single seed. Cerberin is difficult to detect in autopsies and its taste can be masked with strong spices, such as a curry. It is often used in homicide and suicide in India; Kerala's suicide rate is about three times the Indian average. In 2004, a team led by Yvan Gaillard of the Laboratory of Analytical Toxicology in La Voulte-sur-Rhône, France, documented more than 500 cases of fatal Cerbera poisoning between 1989 and 1999 in Kerala. They said "To the best of our knowledge, no plant in the world is responsible for as many deaths by suicide as the odollam tree.' A related species is Cerbera tanghin the seeds of which are known as tanghin poison nut and have been used as an 'ordeal poison'.
- Chelidonium majus (also known as greater celandine). The whole plant is toxic in moderate doses as it contains a range of isoquinoline alkaloids, but there are claimed to be therapeutic uses when used at the correct dosage. The main alkaloid present in the herb and root is coptisine, with berberine, chelidonine, sanguinarine and chelerythrine also present. Sanguinarine is particularly toxic with an LD50 of only 18 mg per kg body weight. The effect of the fresh herb is analgesic, cholagogic, antimicrobial and oncostatic, with action as a central nervous system sedative. In animal tests, Chelidonium majus is shown to be cytostatic. Early studies showed that the latex causes contact dermatitis and eye irritation. Stains on skin of the fingers are sometimes reported to cause eye irritation after rubbing the eyes or handling contact lenses. The characteristic latex also contains proteolytic enzymes and the phytocystatin chelidostatin, a cysteine protease inhibitor.
- Cicuta genus (commonly known as water hemlock, cowbane, wild carrot, snakeweed, poison parsnip, false parsley, children's bane and death-of-man). The root, when freshly pulled out of the ground, is extremely poisonous and contains the toxin cicutoxin, a central nervous system stimulant that induces seizures. When dried, the poisonous effect is reduced. The most common species is C. maculata; one of the species found in the Western USA, C. douglasii, often found in pastures and swamps, has especially thick stems and very large and sturdy flowers which are sometimes harvested for flower displays. This is inadvisable as the sap is also toxic.
- Cleistanthus collinus.
- Colchicum autumnale (commonly known as autumn crocus and meadow saffron). The bulbs contain colchicine. Colchicine poisoning has been compared to arsenic poisoning; symptoms typically start 2 to 5 hours after a toxic dose has been ingested but may take up to 24 hours to appear, and include burning in the mouth and throat, fever, vomiting, diarrhea, abdominal pain and kidney failure. Onset of multiple-system organ failure may occur within 24 to 72 hours. This includes hypovolemic shock due to extreme vascular damage and fluid loss through the GI tract, which may result in death. Additionally, sufferers may experience kidney damage resulting in low urine output and bloody urine, low white blood cell counts (persisting for several days), anemia, muscular weakness, and respiratory failure. Recovery may begin within 6 to 8 days. There is no specific antidote for colchicine, although various treatments do exist. Despite dosing issues concerning its toxicity, colchicine is prescribed in the treatment of gout, familial Mediterranean fever, pericarditis and Behçet's disease. It is also being investigated for its use as an anti-cancer drug.
- Conium maculatum (commonly known as hemlock, poison hemlock, spotted parsley, spotted cowbane, bad-man's oatmeal, poison snakeweed and beaver poison). All parts of the plant contain the alkaloid coniine which causes stomach pains, vomiting, and progressive paralysis of the central nervous system; can be fatal. Not to be confused with hemlock trees (Tsuga spp.), which, while not edible, are not nearly as toxic as the herbaceous plant.
- Consolida subgenus (commonly known as larkspur). Young plants and seeds are poisonous, causing nausea, muscle twitches, and paralysis; often fatal. Other plants in the parent Delphinium genus are also poisonous and commonly called larkspur.
- Convallaria majalis (commonly known as lily of the valley). Contains 38 different cardiac glycosides.
- Coriaria myrtifolia (commonly known as redoul). A Mediterranean plant containing the toxin coriamyrtin, ingestion of which produces digestive, neurological and respiratory problems. The poisonous fruits superficially resemble blackberries and may mistakenly be eaten as such. Can be fatal in children.
- Cytisus scoparius (commonly known as broom or common broom). Contains toxic alkaloids that depress the heart and nervous system. The alkaloid sparteine is a class 1a antiarrhythmic agent, a sodium channel blocker. It is not FDA approved for human use as an antiarrhythmic agent, and it is not included in the Vaughn Williams classification of antiarrhythmic drugs.
- Daphne genus. The berries (either red or yellow) are poisonous, causing burns to mouth and digestive tract, followed by coma; often fatal.
- Datura genus (several species commonly known as jimson weed, thorn apple, stinkweed, Jamestown weed, angel's trumpets, moonflower, and sacred datura). Containing the tropane alkaloids scopolamine, hyoscyamine, and atropine, all parts of these plants are poisonous, especially the seeds and flowers. Ingestion causes abnormal thirst, hyperthermia, severe delirium and incoherence, visual distortions, bizarre and possibly violent behavior, memory loss, coma, and often death; it is a significant poison to grazing livestock in North America. Datura has been used as an entheogenic drug by the indigenous peoples of the Americas and others for centuries, though the extreme variability in a given plant's toxicity depending on its age and growing environment make such usage an exceptionally hazardous practice; the difference between a recreational dose and a lethal dose is minuscule, and incorrect dosage often results in death. For this same reason, Datura has also been a popular poison for suicide and murder, particularly in parts of Europe and India. Reports of recreational usage are overwhelmingly negative; the majority of those who describe their use of Datura find their experiences extremely unpleasant and often physically dangerous.
- Deathcamas. Various genera in the Melanthieae family have species whose common names include "deathcamas", including Amianthium, Anticlea, Stenanthium, Toxicoscordion and Zigadenus. All parts of these plants are toxic, due to the presence of alkaloids. Grazing animals, such as sheep and cattle, may be affected and human fatalities have occurred.
- Delphinium genus (also known as larkspur). Contains the alkaloid delsoline. Young plants and seeds are poisonous, causing nausea, muscle twitches, paralysis, and often death.
- Dendrocnide moroides (also known as stinging tree and gympie gympie). Capable of inflicting a painful sting when touched. The stinging may last for several days and is exacerbated by touching, rubbing, and cold temperatures; can be fatal.
- Dicentra cucullaria (also known as bleeding heart and Dutchman's breeches). Leaves and roots are poisonous and cause convulsions and other nervous symptoms.
- Dichapetalum cymosum (also known as gifblaar). Well known as a livestock poison in South Africa, this plant contains the metabolic poison fluoroacetic acid.
- Dieffenbachia genus (commonly known as dumbcane). All parts are poisonous; the culprits are needle-shaped crystals of calcium oxalate called raphides, which can cause intense burning, reddening of the skin, irritation, and immobility of the tongue, mouth, and throat if ingested. Swelling can be severe enough to block breathing, leading to death, though this is rare; in most cases, symptoms are mild and can be successfully treated with basic analgesics, antihistamines, or charcoal.
- Digitalis purpurea (commonly known as foxglove). The leaves, seeds, and flowers are poisonous, containing cardiac or other steroid glycosides. These cause irregular heartbeat, general digestive upset, and confusion; can be fatal.
- Euonymus europaeus (commonly known as spindle, European spindle or spindle tree). The fruit is poisonous, containing amongst other substances, the alkaloids theobromine and caffeine, as well as an extremely bitter terpene. Poisonings are more common in young children, who are enticed by the brightly coloured fruits. Ingestion can result in liver and kidney damage and even death. There are many other species of Euonymus, many of which are also poisonous.
- Excoecaria agallocha (commonly known as milky mangrove, blind-your-eye mangrove and river poison tree). Contact with latex can cause skin irritation and blistering; eye contact can cause temporary blindness.
- Gelsemium sempervirens (commonly known as yellow jessamine). All parts are poisonous, causing nausea and vomiting. Often fatal. It is possible to become ill from ingesting honey made from jessamine nectar.
- Grevillea sp. (commonly known as silky oak and spiderflower). A few species such as Grevillea 'Robyn Gordon', G. robusta, G. banksii, G. bipinnatifida and others can cause severe contact dermatitis.
- Hedera helix (also known as common ivy). The leaves and berries are poisonous, causing stomach pains, labored breathing, and possible coma.
- Helleborus niger (also known as Christmas rose). Contains protoanemonin, or ranunculin, which has an acrid taste and can cause burning of the eyes, mouth and throat, oral ulceration, gastroenteritis and hematemesis.
- Heracleum mantegazzianum (also known as giant hogweed). The sap is phototoxic, causing phytophotodermatitis (severe skin inflammations) when affected skin is exposed to sunlight or to UV rays. Initially the skin becomes red and starts itching. Then blisters form as the reaction continues over 48 hours. They form black or purplish scars, which can last several years. Hospitalization may become necessary. Presence of minute amounts of sap in the eyes can lead to temporary or even permanent blindness.
- Heracleum sosnowskyi (commonly known as Sosnowsky's Hogweed). Plant has toxic sap and causes skin inflammation on contact.
- Hippomane mancinella (commonly known as manchineel). All parts of this tree, including the fruit, contain toxic phorbol esters typical of the Euphorbiaceae plant family. Specifically the tree contains 12-deoxy-5-hydroxyphorbol-6gamma, 7alpha-oxide, hippomanins, mancinellin, sapogenin, phloracetophenone-2, 4-dimethylether is present in the leaves, while the fruits possess physostigmine. Contact with the milky white latex produces strong allergic dermatitis. Standing beneath the tree during rain will cause blistering of the skin from even slight contact with this liquid (even a small drop of rain with the milky substance in it will cause the skin to blister). Burning tree parts may cause blindness if the smoke reaches the eyes. The fruit can also be fatal if eaten. Many trees carry a warning sign, while others have been marked with a red "X" on the trunk to indicate danger. In the French Antilles the trees are often marked with a painted red band a few feet above the ground. The Caribs used the latex of this tree to poison their arrows and would tie captives to the trunk of the tree, ensuring a slow and painful death. A poultice of arrowroot (Maranta arundinacea) was used by the Arawaks and Taíno as an antidote against such arrow poisons. The Caribs were also known to poison the water supply of their enemies with the leaves. Spanish explorer Juan Ponce de León was struck by an arrow that had been poisoned with manchineel sap during battle with the Calusa in Florida, dying shortly thereafter.
- Hyacinthus orientalis (commonly known as hyacinth). The bulbs are poisonous, causing nausea, vomiting, gasping, convulsions, and possibly death. Even handling the bulbs can cause skin irritation.
- Hyoscyamus niger (commonly known as henbane). Seeds and foliage contain hyoscyamine, scopolamine and other tropane alkaloids. Can produce dilated pupils, hallucinations, increased heart rate, convulsions, vomiting, hypertension and ataxia.
- Ilex aquifolium (commonly known as European holly). The berries cause gastroenteritis, resulting in nausea, vomiting and diarrhea.
- Jacobaea vulgaris (commonly known as ragwort). Contains many different alkaloids, including jacobine, jaconine, jacozine, otosenine, retrorsine, seneciphylline, senecionine, and senkirkine. Poisonous to livestock and hence of concern to people who keep horses and cattle. Horses do not normally eat fresh ragwort due to its bitter taste, however it loses this taste when dried, and becomes dangerous in hay. The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver. Signs that a horse has been poisoned include yellow mucus membranes, depression, and lack of coordination. The danger is that the toxin can have a cumulative effect; the alkaloid does not actually accumulate in the liver but a breakdown product can damage DNA and progressively kills cells. Jacobaea vulgaris is also theoretically poisonous to humans, although poisoning is unlikely as it is distasteful and not used as a food. However, some sensitive individuals can suffer from an allergic skin reaction after handling the plant because, like many members of the Compositae family, it contains sesquiterpine lactones (which are different from the pyrrolizidine alkaloids responsible for the toxic effects), which can cause compositae dermatitis.
- Kalanchoe delagoensis (commonly known as mother of millions). Contains bufadienolide cardiac glycosides which can cause cardiac poisoning, particularly in grazing animals. During 1997, 125 head of cattle died after eating mother-of-millions on a travelling stock reserve near Moree, New South Wales, Australia.
- Kalmia latifolia (commonly known as mountain laurel). Contains andromedotoxin and arbutin. The green parts of the plant, flowers, twigs, and pollen are all toxic, and symptoms of toxicity begin to appear about 6 hours following ingestion. Poisoning produces anorexia, repeated swallowing, profuse salivation, depression, uncoordination, vomiting, frequent defecation, watering of the eyes, irregular or difficult breathing, weakness, cardiac distress, convulsions, coma, and eventually death. Autopsy will show gastrointestinal irritation and hemorrhage.
- Laburnum genus. All parts of the plant and especially the seeds are poisonous and can be lethal if consumed in excess. The main toxin is cytisine, a nicotinic receptor agonist. Symptoms of poisoning may include intense sleepiness, vomiting, excitement, staggering, convulsive movements, slight frothing at the mouth, unequally dilated pupils, coma and death. In some cases, diarrhea is very severe and at times the convulsions are markedly tetanic.
- Ligustrum genus (several species, commonly known as privet). Berries and leaves are poisonous. Berries contain syringin, which causes digestive disturbances and nervous symptoms; can be fatal. Privet is one of several plants which are poisonous to horses. Privet pollen is known to cause asthma and eczema in sufferers. It is banned from sale or cultivation in New Zealand due to the effects of its pollen on asthma sufferers.
- Lilium genus (commonly known as lily). Most have an unidentified water-soluble toxin found in all parts of the plant. Extremely poisonous, yet attractive, to cats, causing acute renal failure; as few as two petals of the flowers can kill.
- Lolium temulentum (commonly called darnel or poison ryegrass). The seeds and seed heads of this common garden weed may contain the alkaloids temuline and loliine. Some experts also point to the fungus ergot or fungi of the genus Endoconidium, both of which grow on the seed heads of rye grasses, as an additional source of toxicity.
- Mandragora officinarum (commonly called mandrake).
- Melianthus major (also called honeybush). All parts of the plant are toxic.
- Menispermum genus (commonly known as moonseed). The fruits and seeds are poisonous, causing nausea and vomiting; often fatal.
- Narcissus genus (various species and garden cultivars commonly known as daffodil). The bulbs are poisonous and cause nausea, vomiting, and diarrhea; can be fatal. Stems also cause headaches, vomiting, and blurred vision.
- Nerium oleander (commonly known as oleander). All parts are toxic, the leaves and woody stems in particular. Contains nerioside, oleandroside, saponins and cardiac glycosides. Causes severe digestive upset, heart trouble and contact dermatitis. The smoke of burning oleander can cause reactions in the lungs, and can be fatal.
- Oenanthe crocata (commonly known as hemlock water dropwort). Contains oenanthotoxin. The leaves may be eaten safely by livestock, but the stems and especially the carbohydrate-rich roots are much more poisonous. Animals familiar with eating the leaves may eat the roots when these are exposed during ditch clearance – one root is sufficient to kill a cow, and human fatalities are also known in these circumstances. Scientists at the University of Eastern Piedmont in Italy claimed to have identified this as the plant responsible for producing the sardonic grin, and it is the most-likely candidate for the "sardonic herb," which was a neurotoxic plant used for the ritual killing of elderly people in Phoenician Sardinia. When these people were unable to support themselves, they were intoxicated with this herb and then dropped from a high rock or beaten to death. Criminals were also executed in this way.
- Passiflora caerulea (also known as the blue passion flower or the common passion flower). The leaves contain cyanogenic glycoside, which breaks down into cyanide.
- Peucedanum galbanum (commonly known as blister bush). All parts are poisonous, and contact causes painful blistering that is intensified with exposure to sunlight.
- Physostigma venenosum (commonly known as calabar bean and also as ordeal beans due to their former use in trials by ordeal). The toxin in the seeds is the parasympathomimetic alkaloid physostigmine, a reversible cholinesterase inhibitor. Symptoms of poisoning include copious saliva, nausea, vomiting, diarrhea, anorexia, dizziness, headache, stomach pain, sweating, dyspepsia and seizures., and can lead to cholinergic syndrome or "SLUDGE syndrome". Medicinal uses of physostigmine include the treatment of myasthenia gravis, glaucoma, Alzheimer's disease and delayed gastric emptying.
- Plumeria genus (commonly known as frangipani). Contact with the milky latex may irritate eyes and skin.
- Phoradendron genus (commonly known as American mistletoe; see also the related Viscum genus). Mistletoe is a common hemiparasite of trees and shrubs. Toxicity varies by species, but all parts of the plant, especially the leaves and berries, contain an array of dangerous chemicals, including proteins called phoratoxins and toxic alkaloids. Symptoms are very similar to those produced by Viscum species and may include acute gastrointestinal discomfort, diarrhea, weak pulse and/or slow heart rate, and even seizures; it is rarely lethal to adult humans, however, and many wild animals are adapted to eating its fruit.
- Phytolacca genus (commonly known as pokeweed). Leaves, berries and roots contain phytolaccatoxin and phytolaccigenin. The toxicity of young leaves can be reduced with repeated boiling and draining. Ingestion of poisonous parts of the plant may cause severe stomach cramping, persistent diarrhea, nausea, vomiting (sometimes bloody), slow and difficult breathing, weakness, spasms, hypertension, severe convulsions, and death.
- Podophyllum peltatum (commonly known as mayapple). Green portions of the plant, unripe fruit, and especially the rhizome contain the non-alkaloid toxin podophyllotoxin, which causes diarrhea and severe digestive upset.
- Pteridium aquilinum (commonly known as bracken). Carcinogenic to humans and animals such as mice, rats, horses and cattle when ingested. The carcinogenic compound is ptaquiloside or PTQ, which can leach from the plant into the water supply, which may explain an increase in the incidence of gastric and oesophageal cancers in humans in bracken-rich areas.
- Quercus genus (several species, commonly known as oak). The leaves and acorns of oak species are poisonous in large amounts to humans and livestock, including cattle, horses, sheep and goats, but not pigs. Poisoning is caused by the toxin tannic acid, which causes gastroenteritis, heart trouble, contact dermatitis and kidney damage. Symptoms of poisoning include lack of appetite, depression, constipation, diarrhea (which may contain blood), blood in urine, and colic; it is rarely fatal, however, and in fact after proper processing acorns are consumed as a staple food in many parts of the world.
- Rhododendron genus (several species including those known as azalea). All parts are poisonous and cause nausea, vomiting, depression, breathing difficulties, and coma, though it is rarely fatal. The primary source of toxicity is a group of closely related compounds called grayanotoxins, which block sodium ion channels in cellular membranes and prevent electrical repolarization during action potentials. Honey made from the nectar of Rhododendron plants may contain dangerous concentrations of grayanotoxins, and has been historically used as a poison and in alcoholic drinks.
- Rhus genus (certain species commonly known as African sumac). Formerly grouped with poison ivy and the rest of the Toxicodendron genus, all parts of this tree contain low levels of a highly irritating oil with urushiol. Skin reactions can include blisters and rashes. The oil spreads readily to clothes and back again, and has a very long life. Infections can follow scratching. As urushiol is not a poison but an allergen, it will not affect certain people. The smoke of burning Rhus lancia can cause reactions in the lungs, and can be fatal.
- Ricinus communis (commonly known as castor oil plant, castor bean and Palma Christi). The seeds contain ricin, an extremely toxic and water-soluble ribosome-inactivating protein; it is also present in lower concentrations in other parts of the plant. Also present are ricinine, an alkaloid, and an irritant oil. According to the 2007 edition of the Guinness Book of World Records, the castor oil plant is the most poisonous in the world, though its cousin abrin, found in the seeds of the jequirity plant, is arguably more lethal. Castor oil, long used as a laxative, muscle rub, and in cosmetics, is made from the seeds, but the ricin protein is denatured during processing. Because ricin can quickly and repeatedly inactivate hundreds of ribosomes in multiple cells, the LD50 in adults is only about 22 μg/kg when injected or inhaled; ingested ricin is much less toxic due to the digestive activity of peptidases, although a dose of 20 to 30 mg/kg, or about 4 to 8 seeds, can still cause death via this route. Reports of actual poisoning are relatively rare. If ingested, symptoms may be delayed by up to 36 hours but commonly begin within 2–4 hours. These include a burning sensation in the mouth and throat, abdominal pain, purging and bloody diarrhea. Within several days there is severe dehydration, a drop in blood pressure and a decrease in urine. Unless treated, death can be expected to occur within 3–5 days; if victims have not succumbed after this time, they often recover. Toxicity varies among animal species: 4 seeds will kill a rabbit, 5 a sheep, 6 an ox or horse, 7 a pig, and 11 a dog. Poisoning occurs when animals ingest broken seeds or break the seed by chewing; intact seeds may pass through the digestive tract without releasing the toxin. Ducks have shown substantial resistance to the seeds: it takes an average of 80 to kill them.
- Robinia genus (also known as black locust and false acacia). All species produce toxic lectins. The poison is a complex mix of lectins with the highest concentration in the fruit and seed, followed by the root bark and the flower. There is little poison in the leaf. The lectins, generally called robin are less toxic than those of e.g. Abrus (abrin) or Ricinus (ricin), and in non-fatal cases the toxic effects tend to be temporary.
- Sambucus genus (commonly known as elder or elderberry). The roots, twigs, leaves, and unripe fruit are considered poisonous and cause nausea and digestive upset. Ripe berries must be cooked before consumption.
- Sanguinaria canadensis (commonly known as bloodroot). The rhizome contains morphine-like benzylisoquinoline alkaloids, primarily the toxin sanguinarine. Sanguinarine kills animal cells by blocking the action of Na+/K+-ATPase transmembrane proteins. As a result, applying S. canadensis to the skin may destroy tissue and lead to the formation of a large scab, called an eschar. Although applying escharotic agents, including S. canadensis, to the skin is sometimes suggested as a home treatment for skin cancer, these attempts can be severely disfiguring, as well as unsuccessful. Case reports have shown that in such instances tumor has recurred and/or metastasized. The United States Food and Drug Administration (FDA) has approved the inclusion of sanguinarine in toothpastes as an antibacterial or anti-plaque agent, although it is believed that this use may cause leukoplakia, a premalignant oral lesion. The safe level of sanguinarine in such products is subject to regulation and debate. S. canadensis extracts have also been promoted by some supplement companies as a treatment or cure for cancer, but the FDA has listed some of these products among its "187 Fake Cancer 'Cures' Consumers Should Avoid". Bloodroot is a popular red natural dye used by Native American artists, especially among southeastern rivercane basketmakers. However, in spite of supposed curative properties and historical use by Native Americans as an emetic, due to its toxicity internal use is not advisable (sanguinarine has an LD50 of only 18 mg per kg body weight).
- Solanum dulcamara (commonly known as bittersweet nightshade). All parts are poisonous, containing solanine and causing fatigue, paralysis, convulsions, and diarrhea. Rarely fatal.
- Solanum nigrum (commonly known as black nightshade). All parts of the plant except the ripe fruit contain the toxic glycoalkaloid solanine. Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, headache and dizziness. In more severe cases, hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils and hypothermia can result. In large quantities, solanine poisoning can be fatal.
- Solanum pseudocapsicum (commonly known as Jerusalem cherry, Madeira winter cherry and winter cherry). All parts, especially the berries, are poisonous, causing nausea and vomiting. It is occasionally fatal, especially to children.
- Sophora secundiflora (commonly known as mescal bean and Texas mountain laurel).
- Strophanthus gratus. The ripe seeds of this African plant contain ouabain, a potent cardiac glycoside that, when sufficiently concentrated, can induce cardiac arrest by binding to and inhibiting the action of the sodium-potassium pump and thereby drastically slowing the contraction of cardiac muscle cells. It was once used medicinally in small doses to treat congestive heart failure and other heart conditions, but has largely been replaced by the structurally related digoxin. Extracts from Strophanthus gratus and the bark of Acokanthera species have long been used by Somali tribesmen to poison hunting arrows; if the concentration is high enough, an arrow poisoned with ouabain can kill an adult hippopotamus.
- Strychnos nux-vomica (commonly known as the strychnine tree). The seeds usually contain about 1.5% strychnine, an extremely bitter and deadly alkaloid. This substance throws a human into intense muscle convulsions and usually kills within three hours. The bark of the tree may also contain brucine, another dangerous chemical.
- Taxus baccata (commonly known as English yew, common yew and graveyard tree). Nearly all parts contain toxic taxanes (except the red, fleshy, and slightly sweet aril surrounding the toxic seeds). The seeds themselves are particularly toxic if chewed. Several people have committed suicide by ingesting leaves and seeds, including Catuvolcus, king of a tribe in what is now Belgium.
- Toxicodendron genus: several species, including Toxicodendron radicans (commonly known as poison ivy), Toxicodendron diversilobum (commonly known as poison-oak), and Toxicodendron vernix (commonly known as poison sumac). All parts of these plants contain a highly irritating oil with urushiol. Skin reactions can include blisters and rashes. The oil spreads readily to clothes and back again, and has a very long life. Infections can follow scratching. Despite the common names, urushiol is actually not a poison but an allergen, and because of this it will not affect certain people. The smoke of burning poison ivy can cause reactions in the lungs, and can be fatal.
- Urtica ferox (commonly known as ongaonga). Even the lightest touch can result in a painful sting that lasts several days.
- Veratrum genus (commonly known as false hellebore and corn lily). Several species, containing highly toxic steroidal alkaloids (e.g. veratridine) that activate sodium ion channels and cause rapid cardiac failure and death if ingested. All parts of the plant are poisonous, with the root and rhizomes being the most toxic. Symptoms typically occur between 30 minutes and 4 hours after ingestion and include nausea and vomiting, abdominal pain, numbness, headache, sweating, muscle weakness, bradycardia, hypotension, cardiac arrhythmia, and seizures. Treatment for poisoning includes gastrointestinal decontamination with activated charcoal followed by supportive care including fluid replacement, antiemetics for persistent nausea and vomiting, atropine for treatment of bradycardia, and vasopressors for the treatment of hypotension. Native Americans used the juice pressed from the roots to poison arrows before combat. The dried powdered root of this plant was also used as an insecticide. The plants' teratogenic properties and ability to induce severe birth defects were well known to Native Americans, although they also used minute amounts of the winter-harvested root (combined with Salvia dorii to potentiate its effects and reduce the toxicity of the herb) to treat cancerous tumors. The toxic steroidal alkaloids are produced only when the plants are in active growth, so herbalists and Native Americans who used this plant for medicinal purposes harvested the roots during the winter months when the levels of toxic constituents were at their lowest. The roots of V. nigrum and V. schindleri have been used in Chinese herbalism (where plants of this genus are known as "li lu" (藜蘆). Li lu is used internally as a powerful emetic of last resort, and topically to kill external parasites, treat tinea and scabies, and stop itching. However some herbalists refuse to prescribe li lu internally, citing the extreme difficulty in preparing a safe and effective dosage, and that death has occurred at a dosage of 0.6 grams. During the 1930s Veratrum extracts were investigated in the treatment of high blood pressure in humans. However patients often suffered side effects due to the narrow therapeutic index of these products. Due to its toxicity, the use of Veratrum as a treatment for high blood pressure in humans was discontinued.
- Viscum genus (commonly known as European mistletoe; see also the related Phoradendron genus). Mistletoe is a common hemiparasite of trees and shrubs. Toxicity varies by species, but all parts of the plant, especially the leaves and berries, contain an array of toxic chemicals, including several different viscotoxins, the alkaloid tyramine, and a ribosome-inactivating lectin called viscumin. Symptoms may include acute gastrointestinal discomfort, diarrhea, weak pulse and/or slow heart rate, and even seizures; it is rarely lethal to adult humans, however, and many wild animals are adapted to eating its fruit.
- Voacanga africana. The bark and seeds of this tropical tree contain a complex mixture of iboga alkaloids, including voacangine and voacamine. These compounds have been variously used as stimulants, psychedelic drugs, and poisons.
- Xanthium genus (several species commonly known as cocklebur). The common cocklebur (Xanthium strumarium), a native of North America, can be poisonous to livestock, including horses, cattle, and sheep. Some domestic animals will avoid consuming the plant if other forage is present, but less discriminating animals, such as pigs, will consume the plants and then sicken and die. The seedlings and seeds are the most toxic parts of the plants. Symptoms usually occur within a few hours, producing unsteadiness and weakness, depression, nausea and vomiting, twisting of the neck muscles, rapid and weak pulse, difficulty breathing, and eventually death. Xanthium has also been used for its medicinal properties and for making yellow dye, as indicated by its name (Greek xanthos = 'yellow').
- Zantedeschia genus (several species, also known as Lily of the Nile and Calla lily). All parts of these plants are toxic, containing calcium oxalate, which induces irritation and swelling of the mouth and throat, acute vomiting and diarrhea. Can be fatal.
|Plant||Fatal to Humans?||Origin and Distribution|
|Aconitum genus||yes||mountainous parts of the northern hemisphere|
|Aesculus hippocastanum||no||South East Europe|
|Agave||no||Mexico, Southeastern United States, South America|
|Ageratina altissima||yes||eastern and central North America|
|Agrostemma githago||yes||United States, parts of Canada, Australia and New Zealand|
|Aquilegia genus||yes||North America|
- List of plants poisonous to equines
- List of poisonous fungi
- Mushroom poisoning
- Psychedelic plants
- Secondary metabolite
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