Plants Poisonous to Animals: Poisoning: The Merck Manual for Pet Health

Poisonous Houseplants and Ornamentals
Common Name	Scientific Name (Family)	Toxic Parts and Effects	Treatment
Autumn crocus, Crocus, Fall crocus, Meadow saffron, Wonder bulb	Colchicum autumnale (Liliaceae, Colchicaceae)	Entire plant is toxic. Milk of lactating animals is a major excretory pathway. Observed signs are thirst, difficult swallowing, abdominal pain, profuse vomiting and diarrhea, weakness, and shock within hours of ingestion. Death from respiratory failure.	Prolonged course due to slow excretion of the toxin. Flush out stomach contents; supportive care for dehydration and electrolyte losses (fluid therapy); central nervous system, circulatory, and respiratory disturbances. Analgesics and atropine recommended for abdominal pain and diarrhea.
Avocado pear, Alligator pear	Persea americana (Lauraceae)	All above-ground parts (leaves in particular) reported toxic to cattle, horses, goats, rabbits, canaries, ostriches, and fish. Toxicity associated with loss of milk production (cattle, rabbits, goats), lung congestion, irregular heart beat, swelling of the jaw, sudden death (rabbits, caged birds, goats), respiratory distress, generalized congestion, subcutaneous swelling, and fluid around the heart (suggestive of cardiac failure, caged birds). In caged birds, signs may be seen within 24 hours (usually after 12 or more hours), with death 1 to 2 days after exposure.	Primarily symptomatic and supportive (see Poisoning: Avocado)
Azalea, Rhododendron	Rhododendron species (Ericaceae)	Entire plant, including pollen and nectar. Within hours of ingestion of toxic dose (1 gram/kilogram), drooling, tearing, vomiting, diarrhea, difficulty breathing, muscle weakness, convulsions, coma, and death. Signs may last several days, but toxin is not cumulative.	Supportive; flush out stomach contents, activated charcoal, saline cathartics, calcium injection, and antibiotics to control possible pneumonia suggested.
Barbados aloe, Curacao aloe	Aloe Barbadensis (Liliaceae)	Latex of the leaves; higher concentrations in younger leaves. Upon eating, causes abrupt, severe diarrhea and/or low blood sugar, with vomiting in some cases.	Supportive; control diarrhea and fluid loss.
Caladium, Fancy leaf caladium, Angel wings	Caladium species (Araceae)	Entire plant is toxic. Ingestion causes immediate intense pain, irritation to mucous membranes, excess drooling, swollen tongue and pharynx, diarrhea, and difficulty breathing. Pets' access to plant associated with rhizomes brought indoors for winter storage.	Supportive
Century plant, American aloe	Agave americana (Agavaceae)	Leaves, seeds, and sap. Upon eating, causes skin and mouth irritation and swelling.	Supportive
Cherry pepper, Chili pepper, Ornamental pepper, Capsicum	Capsicum annuum (Solanaceae)	Capsaicinoids (capsaicin) in the mature fruits, solanine and scopoletin in foliage; irritating to the stomach and intestinal tract, with vomiting and diarrhea. Not likely to be lethal.	Supportive; irritation relief—flush with cool water, topical or oral mineral or vegetable oil. Rarely topical anesthetics.
Chinese evergreen, Painted drop tongue	Aglaonema modestum (Araceae)	Entire plant. Upon eating, causes mouth irritation and swelling.	Supportive
Coontie, Florida arrowroot, Seminole bread, Cycad	Zamia pumila (Zamiaceae)	Leaves, seeds, and stem. Ingestion associated with liver and stomach and intestinal disturbances and incoordination. Signs are persistent vomiting, diarrhea, abdominal pain, depression, and muscular paralysis.	No specific therapy; intravenous fluids and supportive care recommended.
Cyclamen, Snowbread, Shooting star	Cyclamen species (Primulaceae)	Tuberous rhizomes cause stomach and intestine irritation, thereby increasing absorption and severe toxicity. Reduced appetite, diarrhea, convulsions, and paralysis can occur. Pets have greater access to these plants over winter months (both pets and plants are indoors).	Supportive
Daffodils	Narcissus species (Amaryllidaceae)	Same as for hyacinths (see below).	Same as for hyacinths (see below).
Dragon tree	Dracaena species (Agavaceae)	Leaves. Vomiting and severe diarrhea indicative of stomach and intestinal irritation expected. No cases have been reported.	Supportive, to correct fluid and electrolyte (salt) imbalance.
Dumbcane	Dieffenbachia species (Araceae)	Entire plant, including sap. On ingestion, immediate intense pain, burning, and inflammation of mouth and throat, no appetite, vomiting, and possibly diarrhea, with tongue extended, head shaking, excessive drooling, and difficulty breathing. Immediate pain limits amount consumed. Death infrequent.	Supportive
Easter lily, Trumpet lily	Lilium longiflorum; L. tigrinum (Liliaceae)	Entire plant is toxic. Kidney system failure in cats 2 to 4 days post-ingestion. Not reported toxic to other species. Vomiting, depression, loss of appetite within 12 hours post-ingestion.	Emetics (induce vomiting), activated charcoal, saline cathartic, and nursing care—as for renal failure—within hours of ingestion. Delayed treatment is associated with poor prognosis.
English holly, European holly	Ilex aquifolium (Aquifoliaceae)	Leaves, fruits, and seeds. Abdominal pain, vomiting, and diarrhea seen after ingestion of 2 or more berries. Death is rare.	Supportive (at best)
Foxglove	Digitalis purpurea (Scrophulariacae)	Entire plant is toxic. Generally, sudden abdominal pain, vomiting, bloody diarrhea, frequent urination, irregular slow pulse, tremors, convulsions, and rarely death.	Supportive
Hyacinths	Hyacinthus species (Liliaceae)	Bulbs. After ingestion of toxic dose (bulbs), vomiting, diarrhea, and rare deaths reported. Bulbs in storage may be accessible to pets.	Supportive
Jerusalem cherry	Solanum pseudocapsicum (Solanaceae)	Leaves and fruits. Loss of appetite, abdominal pain, vomiting, diarrhea with blood, drooling, progressive weakness or paralysis, difficulty breathing, irregular heartbeat, circulatory collapse, dilated pupils, and convulsions reported.	Supportive; flush out stomach contents, activated charcoal, electrolytes and fluids, and anticonvulsants suggested.
Kalanchoe, Air-plant, Cathedral-bells	Kalanchoe species (Crassulaceae)	Leaves. Within hours of ingesting toxic dose, depression, rapid breathing, teeth grinding, lack of coordination, paralysis, muscle spasms (rabbit), and death (rat).	Supportive; atropine has been effective in rabbits.
Lily-of-the-valley, Conval lily, Mayflower	Convallaria majalis (Liliaceae)	Leaves, flowers, rhizome, and water in which flowers have been kept. Variable period before signs arise depending on dose. Stomach and intestinal signs (vomiting, trembling, abdominal pain, diarrhea), progressive heart irregularities, and death. High blood pressure in sudden cases. Inflammation of the stomach and intestine, bleeding of small capillaries throughout.	Aimed at gut decontamination (flushing of stomach contents) and at correcting irregular heart beats and electrolyte (salt) imbalances. Monitoring of EKG and serum potassium necessary.
Marijuana, Mary Jane, Grass, Pot, Hashish, Indian hemp, Reefer, Weed	Cannabis sativa (Cannabaceae)	Leaves, stems, and flower buds of mature plants. Lethal dose for dogs is more than 3 grams/kilogram body weight. Pets' exposure usually from accidental access to this plant being used for in-home treatment of cancer patient or for illegal recreational uses by owner. Pets (dogs primarily) show incoordination, vomiting, dilated pupils, prolonged depression, excessive or irregular heartbeats, drooling, hyperexcitability, tremors, and fever. Death results when vital central nervous system regulatory centers are severely depressed.	Remove animal from source. Effectiveness of emetics limited by antiemetic effect of THC (the toxic compound in the plant). Oral tannic acid, activated charcoal followed by saline cathartics have been recommended. Stimulants (cardiac and respiratory) along with supportive therapy essential in severely depressed animals. Recovery slow at best (see Poisoning: Marijuana).
Mistletoe	Phoradendron flavescens (Viscaceae)	Entire plant is toxic. Vomiting, profuse diarrhea, dilated pupils, rapid labored breathing, shock, and death from cardiovascular collapse within hours of ingesting toxic dose.	Supportive
Philodendron	Philodendron species (Araceae)	Entire plant is toxic. On ingestion, immediate pain, local irritation to mucous membranes, excessive drooling, swollen tongue and pharynx, difficulty breathing, and kidney system failure. Excitability, nervous spasms, convulsions, and occasional brain swelling reported in cats.	Supportive
Poinsettia, Christmas flower, Christmas star	Euphorbia pulcherrima (Euphorbiaceae)	Milky sap. Irritates mucous membranes and causes excessive drooling and vomiting but not death.	Supportive; flush out stomach contents, activated charcoal, and saline cathartics should be considered.
Sansevieria, Snake plant, Mother-in-law's tongue	Sansevieria species (Agavaceae)	Leaves and flowers. Vomiting, drooling, diarrhea, and rupture of red blood cells related to stomach and intestinal activity of these compounds.	Supportive; fluids and electrolytes may be necessary.
Schefflera, Umbrella tree	Schefflera species (Araliaceae)	Leaves. Mucous membrane irritation, drooling, loss of appetite, vomiting, and if severe enough, diarrhea.	Supportive
Spider plant, St. Bernard's lily, Airplane plant	Chlorophytum species (Liliaceae)	Leaves and plantlets. Vomiting, drooling, retching, and varying degrees of loss of appetite seen in cats within hours of ingestion. Deaths and diarrhea not reported.	Supportive
Yesterday-today-and-tomorrow, Lady-of-the-night	Brunfelsia pauciflora floribunda (Solanaceae)	Flowers, leaves, bark, and roots. Upon eating, animals show abnormal heart rhythms, dry mouth, dilated pupils, difficulty breathing, tremors, depression, urinary retention, and sometimes coma (deep sedation). Not reported to cause death.	In severely depressed animals, stimulants (respiratory and cardiac), along with supportive therapy recommended.
Yew	Taxus species (Taxaceae)	Entire plant except the fleshy aril. Nervousness, trembling, incoordination, difficulty breathing, collapse; irregular heartbeats progressing to the heart stopping and death without struggle. Empty right side of heart; dark, tarry blood in left side of heart.	Supportive at best; usually futile once signs appear. Atropine may be helpful.

Poisonous Range Plants of Temperate North America
Common and Scientific Names	Habitat and Distribution	Affected Animal(s)	Toxic Parts and Effects	Comments and Treatment
Dangerous Season: Spring and Fall
Water hemlock; Cicuta species	Open, moist to wet environments; throughout North America	All	Roots, stem base, young leaves. Toxicity retained when dry, except in hay. Rapid onset of signs, with death in 15 to 30 minutes. Drooling, muscular twitching, dilated pupils. Violent convulsions, coma, death. Poisoning in humans common.	Sedatives to control spasm and heart action. Outlook good if alive 2 hours after ingestion.
Dangerous Season: Spring
African rue; Peganum harmala	Arid to semiarid ranges; southwest	Horses likely	Seeds, leaves, stems; seeds more toxic. Loss of appetite, hindleg weakness, knuckling of fetlock, listlessness, excess drooling, subnormal temperature, frequent urination. Tissue changes include inflammation of the stomach and intestine, with bleeding on heart and under liver capsule.	Unpalatable. Eaten only under drought conditions.
Cocklebur; Xanthium species	Fields, waste places, exposed shores of ponds or rivers; throughout North America. Dangerous season spring and occasionally fall.	All animals	Seeds and young seedlings. Loss of appetite, depression, nausea, vomiting, weakness, rapid weak pulse, difficulty breathing, muscle spasms, convulsions. Tissue changes include inflammation of the stomach, intestines, liver, and kidney.	Seedlings or grain contaminated with seeds. Oils and fats given by mouth may be beneficial; warmth, stimulants given in the muscle.
Death camas; Zygadenus species	Foothill grazing lands, occasionally boggy grasslands, low open woods; throughout North America	Horses	Entire plant. Drooling, vomiting, muscle weakness, incoordination or laying down, fast weak pulse, coma, death. No distinctive tissue changes.	Seeds most toxic. Leaves and stems lose toxicity as plant matures. Atropine and picrotoxin may be effective.
Oaks; Quercus species	Most deciduous woods; throughout North America	Horses	Young leaves and swollen or sprouting acorns. Loss of appetite, constipation, followed by dark tarry diarrhea, dry muzzle, frequent urination, rapid weak pulse, death. Tissue changes include swelling around the kidneys with inflammation, inflammation of the stomach and intestine.	Diet must consist of more than 50% oak buds and young leaves for a period of time. Kidney failure with diet history diagnostic. Treatment symptomatic. Oral ruminatorics helpful. (Also see Poisoning: Quercus Poisoning (Oak Bud Poisoning, Acorn Poisoning).)
Pokeweed, Poke; Phytolacca americana	Disturbed rich soils such as recent clearings, pastures, waste areas; eastern North America	Horses, people	Entire plant; roots most toxic. Vomiting, abdominal pain, bloody diarrhea, low blood cell counts. Terminal convulsions, death from respiratory failure. Tissue changes include open inflammation of the stomach and intestine, bleeding of the mucosa, dark liver.	Oils and protectants (stomach and intestinal tract). Dilute acetic acid orally, stimulants. Blood transfusion (hemolytic anemia).
Dangerous Season: Spring and Summer
Buckeye; Aesculus species	Woods and thickets; eastern US and California	Horses	Entire plant, especially seeds and leaves. Depression, incoordination, twitching, paralysis, inflammation of mucous membranes.	Young shoots and seeds especially poisonous. Stimulants and purgatives.
Coffeepod, Sicklepod; Cassia obtusifolia	Found in cultivated (corn, soybean, or sorghum) and abandoned fields, along fences, roadsides; naturalized in eastern US	Horses	Toxic principles thought to be same as in Cassia occidentalis. Signs, although similar, less severe with Cassia obtusifolia.	Treatment ineffective in down animals.
Coffee senna, Coffee weed, Styptic weed, Wild coffee; Cassia occidentalis	Common along roadsides, waste areas and pastures; naturalized in eastern US	Horses, rabbits	Entire plant. Associated with stomach and intestinal dysfunction and degeneration of muscle. No fever, incoordination with diarrhea and coffee-colored urine. Affected animals are unable to stand but eat and are alert shortly before death. High blood pressure frequent. Tissue changes include heart and skeletal muscle degeneration. Congestion, fatty degeneration and tissue death in the liver and kidneys also reported. Death probably due to high blood pressure causing heart failure.	No specific treatment known. Symptomatic and supportive care essential. Although tissue changes are similar to those of vitamin E/selenium deficiency, this therapy is contraindicated. Remove animals from source.
Fly poison, Staggergrass, Crow poison; Amianthium muscaetoxicum	Open woods, fields, and acid bogs; eastern North America	Horses	Entire plant. Drooling, vomiting, rapid and irregular respiration, weakness, death from respiratory failure.	No practical treatment. Especially dangerous for animals new to pasture. Keep animals well fed.
Larkspurs; Delphinium species	Either cultivated or wild, usually in open foothills or meadows and among aspen; mostly western. Dangerous season spring and summer, also seeds in fall.	Horses	Entire plant, fresh or dry. Straddled stance, arched back, repeated falling, forelegs first. Constipation, bloat, drooling, vomiting. Death (respiratory and heart failure). Most often no tissue changes.	Young plants and seeds more toxic. Toxicity decreases with maturity.
Dangerous Season: Summer and Fall
Black locust, False acacia, Locust tree; Robinia pseudoacacia	Open woods, roadsides, pinelands, on clay soils preferably; eastern US	Horses	Entire plant, although flowers have been suggested as the toxic principles. Diarrhea, loss of appetite, weakness, hind end paralysis, depression, dilated pupils, cold extremities; frequently weak pulse. Death infrequent; recovery period extensive. Tissue changes after death restricted to stomach and intestinal tract.	Laxatives and stimulants suggested. Treatment supportive.
Dogbanes; Apocynum species	Open woods, roadsides, fields; throughout North America	All	Leaves and stems of green or dry plants. Increased temperature and pulse, dilated pupils, loss of appetite, discolored mucous membranes, cold extremities, death.	Intravenous fluids and stomach protectants suggested.
Flatweed, Cat's-ear, Gosmore; Hypochaeris radicata	Native to the Mediterranean and South America; widely distributed in the US, including Pacific, eastern and southeastern states	Horses	Unknown; associated with but not proven cause of a neurologic condition called stringhalt, sudden onset of abnormal gait, knuckling of lower limb joints; paralysis of larynx; recovery possible, but condition could be permanent.	Tranquilizers, sedatives, mephenesin, and thiamine (questionable effectiveness); longterm phenytoin therapy seems helpful. Treatment with baclofen also reported helpful. Surgery reported helpful for gait problems.
Nightshades, Jerusalem cherry, Potato, Horse nettle, Buffalo bur; Solanum species	Fence rows, waste areas, grain and hay fields; throughout North America	All	Leaves, shoots, and unripe berries. Inflammation of the stomach and intestine with bleeding, weakness, excess drooling, difficulty breathing, trembling, progressive paralysis, laying down, death.	Pilocarpine, physostigmine, gastrointestinal protectants. Seeds may contaminate grain.
Perilla mint, Beefsteak plant; Perilla frutescens	Ornamental originally from India, escaped to moist pastures, fields, roadsides, and waste places; eastern North America	Horses	Green or dry plant. Signs 2 to 10 days after exposure include difficulty breathing (especially on exhaling), open-mouth breathing, lowered head, reluctance to move, death on exertion. Tissue changes include fluid and swelling in the lungs.	Treatment ineffective once signs are severe. Injectable steroids, antihistamines, and antibiotics may help. Handle gently (prevents exertion and death).
Red maple; Acer rubrum	Moist land and swamps; eastern North America	Horses	Wilted leaves. Anemia, and destruction of blood cells; weakness, rapid breathing, rapid heart beat, depression, jaundice, poor oxygenation of blood, brownish discoloration of blood and urine.	Not common. Fluids, oxygen, and blood transfusion can be helpful. Methylene blue therapy not rewarding.
Russian knapweed; Centaurea repens	Waste areas, roadsides, railroads, and overgrazed rangeland; not common in cultivated or irrigated pastures; mostly western and upper midwestern US	Horses	Fresh or dried plant. Chronic exposure, but sudden onset of signs. Inability to eat or drink, loss of facial tone, chewing, yawning, standing with head down, severe facial swelling, gait normal, head pressing, aimless walking or excitement most severe the first 2 days, become static thereafter. Death from starvation, dehydration, aspiration pneumonia.	More toxic than yellow star thistle (C. solstitialis; see below) but with similar pathology and prognosis. Some relief with massive doses of atropine but not an effective treatment. Euthanasia recommended.
White snakeroot; Eupatorium rugosum	Woods, cleared areas, waste places, usually the moister and richer soils; eastern North America	Sheep, cattle, horses	Complex benzyl alcohol (tremetol in leaves and stems). Excreted via milk; cumulative. Weight loss, weakness, trembling (muzzle and legs) prominent after exercise, constipation, acetone odor, fatty degeneration of liver, partial paralysis of throat, death in 1 to 3 days.	“Milk sickness” or “trembles.” Supportive treatment. Heart and respiratory stimulants and laxatives may be necessary. Remove animal from access to plant.
Yellow star thistle, Yellow knapweed; Centaurea solstitialis	Waste areas, roadsides, pastures; mostly western North America	Horses	Entire plant. Involuntary chewing movements, twitching of lips, flicking of tongue. Mouth commonly held open. Unable to eat; death from dehydration, starvation, aspiration pneumonia.	Horses graze because of lack of other forage. Extended period of consumption essential for toxicity. Death of certain brain areas is diagnostic. No treatment. Euthanasia recommended.
Dangerous Season: Fall and Winter
Black walnut; Juglans nigra	Native to eastern US; now from eastern seacoast, west to Michigan and most of the Midwest, south to Georgia and Texas	Horses	Shavings with as little as 20% black walnut are toxic within 24 hours of exposure. Reluctance to move; depression; increased temperature, pulse, respiration rate, abdominal sounds, digital pulse, hoof temperature; distal limb swelling; lameness. Severe laminitis with continued exposure.	Nonfatal; laminitis and edema of lower limbs. Remove shavings promptly. Treat for limb edema and laminitis. Improvement in 1 to 2 days with no complications.
Bladderpod, Rattlebox, Sesbane, Coffeebean; Sesbania vesicaria	Mostly open, low ground, abandoned cultivated fields; southeastern US coastal plain	All	Green plant and seeds.	Green seeds are more toxic. Remove animal from source immediately. General supportive treatment—saline purgatives, intravenous fluids.
Onions, (cultivated and wild); Allium cepa, A. canadense	Cultivated and grown on rich soils throughout US	Cattle, horses, dogs	Entire parts. Livestock readily consume onions; low blood cell counts develop within days of exposure. Signs are hemoglobin in the urine, diarrhea, loss of appetite, jaundice, incoordination, collapse, and possible death if untreated. Hemolytic anemia reported in livestock ingesting wild onions. Swollen, pale, dying liver.	Signs similar to toxicity induced by S-methylcysteine sulfoxide (a rare toxic amino acid in Brassica species) in livestock. Susceptibility to onion poisoning varies across animal species: cattle more susceptible than horses and dogs, which are more susceptible than sheep and goats. Remove animals from source and prevent future access to cull onions. Symptomatic and supportive care essential.
Rattlebox, Purple serbane; Daubentonia unica	Cultivated and escaped, in waste places; southeastern US coastal plain	All	Rapid pulse, weak respiration, diarrhea, death.	Seeds poisonous. Remove animal from source. Saline purgatives.
Rayless goldenrod, Burroweed; Haplopappus heterophyllus	Dry plains, grasslands, open woodlands, and along irrigation canals; southwest US	Horses	Primarily nursing young and nonlactating animals. Reluctance to move, trembling, weakness, vomiting, difficulty breathing, constipation, lying down, coma, death.	“Milk sickness.” Separate foals from mares.
Sweet clover, White sweet clover; Melilotus officinalis and M. alba	Commonly found on alkaline soils, fields, roadsides, and waste places; forage crop in southern and northern US	Horses	Also see Poisoning: Sweet Clover Poisoning.	Aslso see Poisoning: Sweet Clover Poisoning.
Dangerous Season: Fall, Winter, and Spring
Chinaberry; Melia azedarach	Fence rows, brush, waste places; southeastern US	Horses	Entire plant, fruit most toxic. Restlessness, vomiting, constipation, blue-tinged gums, rapid pulse, difficulty breathing, death within 24 hours.	Gastroenteritis usual. Recovery may be spontaneous. Laxatives and stomach and intestinal protectants suggested.
Dangerous Season: All Seasons
Astragalus species (certain species only—selenium accumulators)	Areas high in selenium, mostly western and midwestern	Horses	Selenium (chronic). Slow growth, reproductive failure, loss of hair, sore feet, acute death.	Avoid grazing seleniferous plants for extended periods. Also see Poisoning: Selenium Poisoning.
Bracken fern; Pteridium aquilinum	Dry poor soil, open woods, sandy ridges	Horses	Also see Poisoning: Bracken Fern Poisoning.	Also see Poisoning: Bracken Fern Poisoning.
Castor bean; Ricinus communis	Cultivated in southern regions	All	Entire plant, seeds especially toxic. Short to long course (death or recovery). Violent purgation, straining with bloody diarrhea, weakness, drooling, trembling, incoordination.	Diagnosis based on presence of seeds, red blood cell clumping, precipitin test. Specific antiserum, ideal antidote; sedatives, arecoline hydrobromide, followed by saline cathartics suggested.
Chokecherries, Wild cherries, Peaches; Prunus species	Waste areas, fence rows, woods, orchards, prairies, dry slopes	Horses	Excitement leading to depression, difficulty breathing, incoordination, convulsions, prostration. Death may occur in 15 minutes.	Mucous membranes, bright pink color; blood, bright red color (see Poisoning: Cyanide Poisoning).
Corn cockle; Agrostemma githago	Weed, grainfields, and waste areas; throughout North America	All	Seeds. Short course. Profuse watery diarrhea, vomiting, dullness, general weakness, rapid breathing, hemoglobin in the urine, death.	Oils and stomach and intestinal protectants. Neutralize toxin. Blood transfusions may be necessary.
Crotalaria, Rattlebox; Crotalaria species	Fields and roadsides; eastern and central US	All	Entire plant, especially seeds. Chronic course. Horses—unthriftiness, incoordination, walking in circles, jaundice; Death may occur from a few weeks to months after ingestion.	Cumulative, fresh or dry. No treatment.
Day-blooming jessamine and night-blooming jessamine, respectively; Cestrum diurnum, C. nocturnum	Open woods and fields; Gulf Coast states (Florida, Texas) and California	Horses, and dogs (ingesting cholecalciferol-based rodenticides)	Entire plant, including fruit and sap. Inflammation of the stomach and intestine develops on ingestion of fruits. Vomiting, depression, loss of appetite, chronic weight loss with normal appetite, choppy stiff gait, increased pulse, persistent increases in blood calcemia and phosphate, calcium deposits in arteries, tendons, ligaments, and kidneys, destruction of the parathyroid glands, overgrowth of the thyroid gland, and increased bone density reported with chronic ingestion of leaves.	Prevent further access of animals to plants. In early stages, treatment might be effective. Correct fluid and electrolyte (salt) imbalances in cases with persistent vomiting or diarrhea. Reduce or prevent changes in blood calcium. Maintenance therapy of diuretics and steroids may be necessary.
Fraser's photinia, Chinese photinia, Red leaf photinia, Red tip photinia; Photinia fraseri, P. serrulata, P. glabra	Common ornamental (hedge or screen) in southern US	Horses	Same as for Nandina (see below).	Same as for Nandina (see below).
Groundsel, Senecio; Senecio species	Grassland areas; mostly western US	Horses, limited to US	Fresh or dry. Short-term poisoning not common. Dullness, aimless walking, increased pulse, rapid breathing, weakness, colic, delayed death (days to months). Nervous signs evident in later stages.	Liver biopsy diagnostic in early stages. No general treatment.
Hound's tongue; Cynoglossum officinale	Common in waste places, roadsides, and pastured areas throughout US	Horses	Foliage. Unpleasant odor discourages consumption when fresh, becomes palatable in hay and is readily consumed. Signs are poor appetite, depression, rough hair coat, bleeding, bloody feces, incoordination, jaundice, death.	Know source and quality of hay. Treatment symptomatic and supportive at best. Affected animals seldom recover.
Jimson weed, Thorn apple; Datura stramonium	Fields, barn lots, trampled pastures, and waste places on rich bottom soils; throughout North America	All	Entire plant, seeds in particular. Short course. Weak rapid pulse and heartbeat, dilated pupils, dry mouth, incoordination, convulsions, coma.	All parts, mainly in hay or silage. Urine from animal dilates pupils of laboratory animals (diagnostic). Treatment nonspecific; cardiac and respiratory stimulants.
Johnson grass; Sorghum halepense	Weed of open fields and waste places; southern and scattered north to New York and Iowa	Horses	Same as for Sorghum vulgare (see below).	Same as for Sorghum vulgare (see below).
Laurel, Ivybush, Lambkill; Kalmia species	Rich moist woods, meadows, or acid bogs; eastern and northwestern North America. Dangerous all seasons, especially winter and spring.	Horses	Vegetative parts. Short course. Incoordination, excess drooling, vomiting, bloat, weakness, muscular spasms, coma, death.	Treatment includes laxatives, demulcents, nerve stimulants, atropine.
Laurel cherry, Cherry laurel; Prunus caroliniana	Woods, fence rows, and often escaped from cultivation; southern regions. Dangerous all seasons, especially winter and spring.	Horses	Wilted leaves, bark, and twigs. Short course. Difficult breathing, bloat, staggering, convulsions, followed by prostration and death. Mucous membranes and blood bright red.	Also see Poisoning: Cyanide Poisoning.
Locoweed; Astragalus species, Oxytropis species (certain species only)	Mostly western North America	All grazing animals	Depression, emaciation, incoordination, dry lusterless hair. Abortions.	Avoid grazing of source. Both green and dry plants toxic.
Lupines, Bluebonnet; Lupinus species	Dry to moist soils, roadsides, fields, and mountains; throughout, but poisoning mostly western North America	Horses	Seeds (fresh and dry). Short course. No appetite, difficulty breathing, struggle, convulsions, death from respiratory paralysis.	Do not disturb sick animals; remove from source as they begin to recover. No effective treatment, but survivors recover completely. Also see Poisoning: Mycotoxic Lupinosis.
Milk vetch (and many other common names); Astragalus species (certain species only)	Nearly all	Horses	Hindlimb paralysis, goose-stepping, depression, rough coat, pulmonary emphysema, sudden death, spinal cord changes.	Avoid grazing of pre-flower stage.
Milkweeds; Asclepias species	Dry areas, usually waste places, roadsides, streambeds	All	Entire plant, green or dry. Staggering, tetanic convulsions, bloating, difficulty breathing, dilated pupils, rapid and weak pulse, coma, death.	Sedatives, laxatives, and intravenous fluids suggested.
Mustards, Crucifers, Cress; Brassica, Raphanus, Descurainia species	Fields, roadsides; throughout North America	Horses	Seeds and vegetative parts, fresh or dry. Sudden or long course. Loss of appetite, severe inflammation of the stomach and intestines, drooling, diarrhea, paralysis, sensitivity to light, hemoglobin in the urine.	Remove from source. Administer stomach and intestinal protectants (mineral oil).
Nandina, Heavenly bamboo, Chinese sacred bamboo; Nandina domestica	Common ornamental in southern US	Horses	Foliage and fruits. Hydrolyzed in stomach and intestinal tract to free cyanide, thereby affecting cellular respiration. Prognosis good if animal survives for 1 hour after signs begin. Also see Poisoning: Cyanide Poisoning.	Acute outcome precludes effective treatment for most; Intravenous sodium nitrite/sodium thiosulfate treatment of choice. Picrate test indicates toxic potential of the plant. Also see Poisoning: Cyanide Poisoning.
Oleander; Nerium oleander	Common ornamental in southern regions of the US	All	Entire plant, fresh or dry. Short course. Severe inflammation of the intestine and stomach, vomiting, diarrhea, increased pulse rate, weakness, death.	No specific treatment. Atropine in conjunction with propranolol reported helpful.
Poison hemlock; Conium maculatum	Roadside ditches, damp waste areas; throughout North America	All	Vegetative parts. Short course. Dilated pupils; weakness; staggering gait; slow pulse, progressing to rapid and thready. Slow, irregular breathing; death from respiratory failure.	Toxin excreted via lungs and kidneys, mousy odor of breath and urine diagnostic. Administer saline cathartics; neutralize alkaloids with tannic acid, together with stimulants.
Privet, Ligustrum, Hedge plant; Ligustrum species	An ornamental; common as hedge; found at abandoned farm home sites, along fences, and in bottomlands.	Horses	Leaves and fruit. Primarily intestine and stomach irritants. Diarrhea, abdominal pain, incoordination, muscle weakness, weak pulse, fever, convulsions, sometimes death.	Treatment symptomatic and supportive; correct dehydration.
Sorghum, Sudan grass, Kafir, Durra, Milo, Broom-corn, Schrock; Sorghum vulgare	Forage crops and escapes; throughout North America	All	Heavy in vegetative parts. Short course. Difficult breathing, bloat, staggering, convulsions, death. Blood bright red (cyanide) or chocolate brown (nitrate).	Hay safe for cyanide (volatile), not safe for nitrate (analyze). Also see Poisoning: Cyanide Poisoning and see Poisoning: Nitrate and Nitrite Poisoning.
St. John's-wort, Goatweed, Klamath weed; Hypericum perforatum	Dry soil, roadsides, pastures, ranges; throughout North America	Horses	Photodynamic pigment (hypericin). Short course. Sensitivity to light, pruritus and erythema, blindness, convulsions, diarrhea, hypersensitivity to cold water contact, death.	Remove animals from source and sunlight. Corticosteroids given by injection, topical antibiotics.
Tall fescue; Festuca arundinacea	A coarse, hardy, drought-resistant grass; Pacific Northwest, Missouri, Oklahoma, and Kentucky; major pasture grass in southeastern US	Horses	Also see see Poisoning: Fescue Poisoning (Summer Fescue Poisoning).	Also see see Poisoning: Fescue Poisoning (Summer Fescue Poisoning).
Yellow jessamine, Evening trumpet flower, Carolina Jessamine; Gelsemium sempervirens	Open woods, thickets; southeast	All	Entire plant. Short course. Weakness, incoordination, dilated pupils, convulsions, coma, death within 48 hours.	No specific treatment. Relaxants and sedatives suggested.
Yew; Taxus species	Most of North America; Japanese and English yew common ornamentals	All	Bark, leaves, seeds. Gaseous distress, diarrhea, vomiting, tremors, difficulty breathing, dilated pupils, respiratory difficulty, weakness, fatigue, collapse, coma, convulsions, irregular heartbeat, circulatory failure, death. Death may be rapid.	Poisoning usually results when branches and trimmings fed to livestock.

Poisonous Range Plants of Temperate North America

Common and Scientific Names

Habitat and Distribution

Affected Animal(s)

Toxic Parts and Effects

Comments and Treatment

Dangerous Season: Spring and Fall
Water hemlock; Cicuta species	Open, moist to wet environments; throughout North America	All	Roots, stem base, young leaves. Toxicity retained when dry, except in hay. Rapid onset of signs, with death in 15 to 30 minutes. Drooling, muscular twitching, dilated pupils. Violent convulsions, coma, death. Poisoning in humans common.	Sedatives to control spasm and heart action. Outlook good if alive 2 hours after ingestion.
Dangerous Season: Spring
African rue; Peganum harmala	Arid to semiarid ranges; southwest	Horses likely	Seeds, leaves, stems; seeds more toxic. Loss of appetite, hindleg weakness, knuckling of fetlock, listlessness, excess drooling, subnormal temperature, frequent urination. Tissue changes include inflammation of the stomach and intestine, with bleeding on heart and under liver capsule.	Unpalatable. Eaten only under drought conditions.
Cocklebur; Xanthium species	Fields, waste places, exposed shores of ponds or rivers; throughout North America. Dangerous season spring and occasionally fall.	All animals	Seeds and young seedlings. Loss of appetite, depression, nausea, vomiting, weakness, rapid weak pulse, difficulty breathing, muscle spasms, convulsions. Tissue changes include inflammation of the stomach, intestines, liver, and kidney.	Seedlings or grain contaminated with seeds. Oils and fats given by mouth may be beneficial; warmth, stimulants given in the muscle.
Death camas; Zygadenus species	Foothill grazing lands, occasionally boggy grasslands, low open woods; throughout North America	Horses	Entire plant. Drooling, vomiting, muscle weakness, incoordination or laying down, fast weak pulse, coma, death. No distinctive tissue changes.	Seeds most toxic. Leaves and stems lose toxicity as plant matures. Atropine and picrotoxin may be effective.
Oaks; Quercus species	Most deciduous woods; throughout North America	Horses	Young leaves and swollen or sprouting acorns. Loss of appetite, constipation, followed by dark tarry diarrhea, dry muzzle, frequent urination, rapid weak pulse, death. Tissue changes include swelling around the kidneys with inflammation, inflammation of the stomach and intestine.	Diet must consist of more than 50% oak buds and young leaves for a period of time. Kidney failure with diet history diagnostic. Treatment symptomatic. Oral ruminatorics helpful. (Also see Poisoning: Quercus Poisoning (Oak Bud Poisoning, Acorn Poisoning).)
Pokeweed, Poke; Phytolacca americana	Disturbed rich soils such as recent clearings, pastures, waste areas; eastern North America	Horses, people	Entire plant; roots most toxic. Vomiting, abdominal pain, bloody diarrhea, low blood cell counts. Terminal convulsions, death from respiratory failure. Tissue changes include open inflammation of the stomach and intestine, bleeding of the mucosa, dark liver.	Oils and protectants (stomach and intestinal tract). Dilute acetic acid orally, stimulants. Blood transfusion (hemolytic anemia).
Dangerous Season: Spring and Summer
Buckeye; Aesculus species	Woods and thickets; eastern US and California	Horses	Entire plant, especially seeds and leaves. Depression, incoordination, twitching, paralysis, inflammation of mucous membranes.	Young shoots and seeds especially poisonous. Stimulants and purgatives.
Coffeepod, Sicklepod; Cassia obtusifolia	Found in cultivated (corn, soybean, or sorghum) and abandoned fields, along fences, roadsides; naturalized in eastern US	Horses	Toxic principles thought to be same as in Cassia occidentalis. Signs, although similar, less severe with Cassia obtusifolia.	Treatment ineffective in down animals.
Coffee senna, Coffee weed, Styptic weed, Wild coffee; Cassia occidentalis	Common along roadsides, waste areas and pastures; naturalized in eastern US	Horses, rabbits	Entire plant. Associated with stomach and intestinal dysfunction and degeneration of muscle. No fever, incoordination with diarrhea and coffee-colored urine. Affected animals are unable to stand but eat and are alert shortly before death. High blood pressure frequent. Tissue changes include heart and skeletal muscle degeneration. Congestion, fatty degeneration and tissue death in the liver and kidneys also reported. Death probably due to high blood pressure causing heart failure.	No specific treatment known. Symptomatic and supportive care essential. Although tissue changes are similar to those of vitamin E/selenium deficiency, this therapy is contraindicated. Remove animals from source.
Fly poison, Staggergrass, Crow poison; Amianthium muscaetoxicum	Open woods, fields, and acid bogs; eastern North America	Horses	Entire plant. Drooling, vomiting, rapid and irregular respiration, weakness, death from respiratory failure.	No practical treatment. Especially dangerous for animals new to pasture. Keep animals well fed.
Larkspurs; Delphinium species	Either cultivated or wild, usually in open foothills or meadows and among aspen; mostly western. Dangerous season spring and summer, also seeds in fall.	Horses	Entire plant, fresh or dry. Straddled stance, arched back, repeated falling, forelegs first. Constipation, bloat, drooling, vomiting. Death (respiratory and heart failure). Most often no tissue changes.	Young plants and seeds more toxic. Toxicity decreases with maturity.
Dangerous Season: Summer and Fall
Black locust, False acacia, Locust tree; Robinia pseudoacacia	Open woods, roadsides, pinelands, on clay soils preferably; eastern US	Horses	Entire plant, although flowers have been suggested as the toxic principles. Diarrhea, loss of appetite, weakness, hind end paralysis, depression, dilated pupils, cold extremities; frequently weak pulse. Death infrequent; recovery period extensive. Tissue changes after death restricted to stomach and intestinal tract.	Laxatives and stimulants suggested. Treatment supportive.
Dogbanes; Apocynum species	Open woods, roadsides, fields; throughout North America	All	Leaves and stems of green or dry plants. Increased temperature and pulse, dilated pupils, loss of appetite, discolored mucous membranes, cold extremities, death.	Intravenous fluids and stomach protectants suggested.
Flatweed, Cat's-ear, Gosmore; Hypochaeris radicata	Native to the Mediterranean and South America; widely distributed in the US, including Pacific, eastern and southeastern states	Horses	Unknown; associated with but not proven cause of a neurologic condition called stringhalt, sudden onset of abnormal gait, knuckling of lower limb joints; paralysis of larynx; recovery possible, but condition could be permanent.	Tranquilizers, sedatives, mephenesin, and thiamine (questionable effectiveness); longterm phenytoin therapy seems helpful. Treatment with baclofen also reported helpful. Surgery reported helpful for gait problems.
Nightshades, Jerusalem cherry, Potato, Horse nettle, Buffalo bur; Solanum species	Fence rows, waste areas, grain and hay fields; throughout North America	All	Leaves, shoots, and unripe berries. Inflammation of the stomach and intestine with bleeding, weakness, excess drooling, difficulty breathing, trembling, progressive paralysis, laying down, death.	Pilocarpine, physostigmine, gastrointestinal protectants. Seeds may contaminate grain.
Perilla mint, Beefsteak plant; Perilla frutescens	Ornamental originally from India, escaped to moist pastures, fields, roadsides, and waste places; eastern North America	Horses	Green or dry plant. Signs 2 to 10 days after exposure include difficulty breathing (especially on exhaling), open-mouth breathing, lowered head, reluctance to move, death on exertion. Tissue changes include fluid and swelling in the lungs.	Treatment ineffective once signs are severe. Injectable steroids, antihistamines, and antibiotics may help. Handle gently (prevents exertion and death).
Red maple; Acer rubrum	Moist land and swamps; eastern North America	Horses	Wilted leaves. Anemia, and destruction of blood cells; weakness, rapid breathing, rapid heart beat, depression, jaundice, poor oxygenation of blood, brownish discoloration of blood and urine.	Not common. Fluids, oxygen, and blood transfusion can be helpful. Methylene blue therapy not rewarding.
Russian knapweed; Centaurea repens	Waste areas, roadsides, railroads, and overgrazed rangeland; not common in cultivated or irrigated pastures; mostly western and upper midwestern US	Horses	Fresh or dried plant. Chronic exposure, but sudden onset of signs. Inability to eat or drink, loss of facial tone, chewing, yawning, standing with head down, severe facial swelling, gait normal, head pressing, aimless walking or excitement most severe the first 2 days, become static thereafter. Death from starvation, dehydration, aspiration pneumonia.	More toxic than yellow star thistle (C. solstitialis; see below) but with similar pathology and prognosis. Some relief with massive doses of atropine but not an effective treatment. Euthanasia recommended.
White snakeroot; Eupatorium rugosum	Woods, cleared areas, waste places, usually the moister and richer soils; eastern North America	Sheep, cattle, horses	Complex benzyl alcohol (tremetol in leaves and stems). Excreted via milk; cumulative. Weight loss, weakness, trembling (muzzle and legs) prominent after exercise, constipation, acetone odor, fatty degeneration of liver, partial paralysis of throat, death in 1 to 3 days.	“Milk sickness” or “trembles.” Supportive treatment. Heart and respiratory stimulants and laxatives may be necessary. Remove animal from access to plant.
Yellow star thistle, Yellow knapweed; Centaurea solstitialis	Waste areas, roadsides, pastures; mostly western North America	Horses	Entire plant. Involuntary chewing movements, twitching of lips, flicking of tongue. Mouth commonly held open. Unable to eat; death from dehydration, starvation, aspiration pneumonia.	Horses graze because of lack of other forage. Extended period of consumption essential for toxicity. Death of certain brain areas is diagnostic. No treatment. Euthanasia recommended.
Dangerous Season: Fall and Winter
Black walnut; Juglans nigra	Native to eastern US; now from eastern seacoast, west to Michigan and most of the Midwest, south to Georgia and Texas	Horses	Shavings with as little as 20% black walnut are toxic within 24 hours of exposure. Reluctance to move; depression; increased temperature, pulse, respiration rate, abdominal sounds, digital pulse, hoof temperature; distal limb swelling; lameness. Severe laminitis with continued exposure.	Nonfatal; laminitis and edema of lower limbs. Remove shavings promptly. Treat for limb edema and laminitis. Improvement in 1 to 2 days with no complications.
Bladderpod, Rattlebox, Sesbane, Coffeebean; Sesbania vesicaria	Mostly open, low ground, abandoned cultivated fields; southeastern US coastal plain	All	Green plant and seeds.	Green seeds are more toxic. Remove animal from source immediately. General supportive treatment—saline purgatives, intravenous fluids.
Onions, (cultivated and wild); Allium cepa, A. canadense	Cultivated and grown on rich soils throughout US	Cattle, horses, dogs	Entire parts. Livestock readily consume onions; low blood cell counts develop within days of exposure. Signs are hemoglobin in the urine, diarrhea, loss of appetite, jaundice, incoordination, collapse, and possible death if untreated. Hemolytic anemia reported in livestock ingesting wild onions. Swollen, pale, dying liver.	Signs similar to toxicity induced by S-methylcysteine sulfoxide (a rare toxic amino acid in Brassica species) in livestock. Susceptibility to onion poisoning varies across animal species: cattle more susceptible than horses and dogs, which are more susceptible than sheep and goats. Remove animals from source and prevent future access to cull onions. Symptomatic and supportive care essential.
Rattlebox, Purple serbane; Daubentonia unica	Cultivated and escaped, in waste places; southeastern US coastal plain	All	Rapid pulse, weak respiration, diarrhea, death.	Seeds poisonous. Remove animal from source. Saline purgatives.
Rayless goldenrod, Burroweed; Haplopappus heterophyllus	Dry plains, grasslands, open woodlands, and along irrigation canals; southwest US	Horses	Primarily nursing young and nonlactating animals. Reluctance to move, trembling, weakness, vomiting, difficulty breathing, constipation, lying down, coma, death.	“Milk sickness.” Separate foals from mares.
Sweet clover, White sweet clover; Melilotus officinalis and M. alba	Commonly found on alkaline soils, fields, roadsides, and waste places; forage crop in southern and northern US	Horses	Also see Poisoning: Sweet Clover Poisoning.	Aslso see Poisoning: Sweet Clover Poisoning.
Dangerous Season: Fall, Winter, and Spring
Chinaberry; Melia azedarach	Fence rows, brush, waste places; southeastern US	Horses	Entire plant, fruit most toxic. Restlessness, vomiting, constipation, blue-tinged gums, rapid pulse, difficulty breathing, death within 24 hours.	Gastroenteritis usual. Recovery may be spontaneous. Laxatives and stomach and intestinal protectants suggested.
Dangerous Season: All Seasons
Astragalus species (certain species only—selenium accumulators)	Areas high in selenium, mostly western and midwestern	Horses	Selenium (chronic). Slow growth, reproductive failure, loss of hair, sore feet, acute death.	Avoid grazing seleniferous plants for extended periods. Also see Poisoning: Selenium Poisoning.
Bracken fern; Pteridium aquilinum	Dry poor soil, open woods, sandy ridges	Horses	Also see Poisoning: Bracken Fern Poisoning.	Also see Poisoning: Bracken Fern Poisoning.
Castor bean; Ricinus communis	Cultivated in southern regions	All	Entire plant, seeds especially toxic. Short to long course (death or recovery). Violent purgation, straining with bloody diarrhea, weakness, drooling, trembling, incoordination.	Diagnosis based on presence of seeds, red blood cell clumping, precipitin test. Specific antiserum, ideal antidote; sedatives, arecoline hydrobromide, followed by saline cathartics suggested.
Chokecherries, Wild cherries, Peaches; Prunus species	Waste areas, fence rows, woods, orchards, prairies, dry slopes	Horses	Excitement leading to depression, difficulty breathing, incoordination, convulsions, prostration. Death may occur in 15 minutes.	Mucous membranes, bright pink color; blood, bright red color (see Poisoning: Cyanide Poisoning).
Corn cockle; Agrostemma githago	Weed, grainfields, and waste areas; throughout North America	All	Seeds. Short course. Profuse watery diarrhea, vomiting, dullness, general weakness, rapid breathing, hemoglobin in the urine, death.	Oils and stomach and intestinal protectants. Neutralize toxin. Blood transfusions may be necessary.
Crotalaria, Rattlebox; Crotalaria species	Fields and roadsides; eastern and central US	All	Entire plant, especially seeds. Chronic course. Horses—unthriftiness, incoordination, walking in circles, jaundice; Death may occur from a few weeks to months after ingestion.	Cumulative, fresh or dry. No treatment.
Day-blooming jessamine and night-blooming jessamine, respectively; Cestrum diurnum, C. nocturnum	Open woods and fields; Gulf Coast states (Florida, Texas) and California	Horses, and dogs (ingesting cholecalciferol-based rodenticides)	Entire plant, including fruit and sap. Inflammation of the stomach and intestine develops on ingestion of fruits. Vomiting, depression, loss of appetite, chronic weight loss with normal appetite, choppy stiff gait, increased pulse, persistent increases in blood calcemia and phosphate, calcium deposits in arteries, tendons, ligaments, and kidneys, destruction of the parathyroid glands, overgrowth of the thyroid gland, and increased bone density reported with chronic ingestion of leaves.	Prevent further access of animals to plants. In early stages, treatment might be effective. Correct fluid and electrolyte (salt) imbalances in cases with persistent vomiting or diarrhea. Reduce or prevent changes in blood calcium. Maintenance therapy of diuretics and steroids may be necessary.
Fraser's photinia, Chinese photinia, Red leaf photinia, Red tip photinia; Photinia fraseri, P. serrulata, P. glabra	Common ornamental (hedge or screen) in southern US	Horses	Same as for Nandina (see below).	Same as for Nandina (see below).
Groundsel, Senecio; Senecio species	Grassland areas; mostly western US	Horses, limited to US	Fresh or dry. Short-term poisoning not common. Dullness, aimless walking, increased pulse, rapid breathing, weakness, colic, delayed death (days to months). Nervous signs evident in later stages.	Liver biopsy diagnostic in early stages. No general treatment.
Hound's tongue; Cynoglossum officinale	Common in waste places, roadsides, and pastured areas throughout US	Horses	Foliage. Unpleasant odor discourages consumption when fresh, becomes palatable in hay and is readily consumed. Signs are poor appetite, depression, rough hair coat, bleeding, bloody feces, incoordination, jaundice, death.	Know source and quality of hay. Treatment symptomatic and supportive at best. Affected animals seldom recover.
Jimson weed, Thorn apple; Datura stramonium	Fields, barn lots, trampled pastures, and waste places on rich bottom soils; throughout North America	All	Entire plant, seeds in particular. Short course. Weak rapid pulse and heartbeat, dilated pupils, dry mouth, incoordination, convulsions, coma.	All parts, mainly in hay or silage. Urine from animal dilates pupils of laboratory animals (diagnostic). Treatment nonspecific; cardiac and respiratory stimulants.
Johnson grass; Sorghum halepense	Weed of open fields and waste places; southern and scattered north to New York and Iowa	Horses	Same as for Sorghum vulgare (see below).	Same as for Sorghum vulgare (see below).
Laurel, Ivybush, Lambkill; Kalmia species	Rich moist woods, meadows, or acid bogs; eastern and northwestern North America. Dangerous all seasons, especially winter and spring.	Horses	Vegetative parts. Short course. Incoordination, excess drooling, vomiting, bloat, weakness, muscular spasms, coma, death.	Treatment includes laxatives, demulcents, nerve stimulants, atropine.
Laurel cherry, Cherry laurel; Prunus caroliniana	Woods, fence rows, and often escaped from cultivation; southern regions. Dangerous all seasons, especially winter and spring.	Horses	Wilted leaves, bark, and twigs. Short course. Difficult breathing, bloat, staggering, convulsions, followed by prostration and death. Mucous membranes and blood bright red.	Also see Poisoning: Cyanide Poisoning.
Locoweed; Astragalus species, Oxytropis species (certain species only)	Mostly western North America	All grazing animals	Depression, emaciation, incoordination, dry lusterless hair. Abortions.	Avoid grazing of source. Both green and dry plants toxic.
Lupines, Bluebonnet; Lupinus species	Dry to moist soils, roadsides, fields, and mountains; throughout, but poisoning mostly western North America	Horses	Seeds (fresh and dry). Short course. No appetite, difficulty breathing, struggle, convulsions, death from respiratory paralysis.	Do not disturb sick animals; remove from source as they begin to recover. No effective treatment, but survivors recover completely. Also see Poisoning: Mycotoxic Lupinosis.
Milk vetch (and many other common names); Astragalus species (certain species only)	Nearly all	Horses	Hindlimb paralysis, goose-stepping, depression, rough coat, pulmonary emphysema, sudden death, spinal cord changes.	Avoid grazing of pre-flower stage.
Milkweeds; Asclepias species	Dry areas, usually waste places, roadsides, streambeds	All	Entire plant, green or dry. Staggering, tetanic convulsions, bloating, difficulty breathing, dilated pupils, rapid and weak pulse, coma, death.	Sedatives, laxatives, and intravenous fluids suggested.
Mustards, Crucifers, Cress; Brassica, Raphanus, Descurainia species	Fields, roadsides; throughout North America	Horses	Seeds and vegetative parts, fresh or dry. Sudden or long course. Loss of appetite, severe inflammation of the stomach and intestines, drooling, diarrhea, paralysis, sensitivity to light, hemoglobin in the urine.	Remove from source. Administer stomach and intestinal protectants (mineral oil).
Nandina, Heavenly bamboo, Chinese sacred bamboo; Nandina domestica	Common ornamental in southern US	Horses	Foliage and fruits. Hydrolyzed in stomach and intestinal tract to free cyanide, thereby affecting cellular respiration. Prognosis good if animal survives for 1 hour after signs begin. Also see Poisoning: Cyanide Poisoning.	Acute outcome precludes effective treatment for most; Intravenous sodium nitrite/sodium thiosulfate treatment of choice. Picrate test indicates toxic potential of the plant. Also see Poisoning: Cyanide Poisoning.
Oleander; Nerium oleander	Common ornamental in southern regions of the US	All	Entire plant, fresh or dry. Short course. Severe inflammation of the intestine and stomach, vomiting, diarrhea, increased pulse rate, weakness, death.	No specific treatment. Atropine in conjunction with propranolol reported helpful.
Poison hemlock; Conium maculatum	Roadside ditches, damp waste areas; throughout North America	All	Vegetative parts. Short course. Dilated pupils; weakness; staggering gait; slow pulse, progressing to rapid and thready. Slow, irregular breathing; death from respiratory failure.	Toxin excreted via lungs and kidneys, mousy odor of breath and urine diagnostic. Administer saline cathartics; neutralize alkaloids with tannic acid, together with stimulants.
Privet, Ligustrum, Hedge plant; Ligustrum species	An ornamental; common as hedge; found at abandoned farm home sites, along fences, and in bottomlands.	Horses	Leaves and fruit. Primarily intestine and stomach irritants. Diarrhea, abdominal pain, incoordination, muscle weakness, weak pulse, fever, convulsions, sometimes death.	Treatment symptomatic and supportive; correct dehydration.
Sorghum, Sudan grass, Kafir, Durra, Milo, Broom-corn, Schrock; Sorghum vulgare	Forage crops and escapes; throughout North America	All	Heavy in vegetative parts. Short course. Difficult breathing, bloat, staggering, convulsions, death. Blood bright red (cyanide) or chocolate brown (nitrate).	Hay safe for cyanide (volatile), not safe for nitrate (analyze). Also see Poisoning: Cyanide Poisoning and see Poisoning: Nitrate and Nitrite Poisoning.
St. John's-wort, Goatweed, Klamath weed; Hypericum perforatum	Dry soil, roadsides, pastures, ranges; throughout North America	Horses	Photodynamic pigment (hypericin). Short course. Sensitivity to light, pruritus and erythema, blindness, convulsions, diarrhea, hypersensitivity to cold water contact, death.	Remove animals from source and sunlight. Corticosteroids given by injection, topical antibiotics.
Tall fescue; Festuca arundinacea	A coarse, hardy, drought-resistant grass; Pacific Northwest, Missouri, Oklahoma, and Kentucky; major pasture grass in southeastern US	Horses	Also see see Poisoning: Fescue Poisoning (Summer Fescue Poisoning).	Also see see Poisoning: Fescue Poisoning (Summer Fescue Poisoning).
Yellow jessamine, Evening trumpet flower, Carolina Jessamine; Gelsemium sempervirens	Open woods, thickets; southeast	All	Entire plant. Short course. Weakness, incoordination, dilated pupils, convulsions, coma, death within 48 hours.	No specific treatment. Relaxants and sedatives suggested.
Yew; Taxus species	Most of North America; Japanese and English yew common ornamentals	All	Bark, leaves, seeds. Gaseous distress, diarrhea, vomiting, tremors, difficulty breathing, dilated pupils, respiratory difficulty, weakness, fatigue, collapse, coma, convulsions, irregular heartbeat, circulatory failure, death. Death may be rapid.	Poisoning usually results when branches and trimmings fed to livestock.