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Poisonous Range Plants of Temperate North America a

Poisonous Range Plants of Temperate North America a

Scientific and Common Names

Habitat and Distribution

Affected Animals

Important Characteristics

Toxic Principle and Effects

Comments and Treatment

Dangerous Season: Spring and Fall

Allamanda cathartica, A blanchetti (Apocynaceae)

Allamanda, Yellow allamanda, Golden trumpet, Purple allamanda

Native to tropical America (2 cultivated taxa in North America); indoors and as ornamentals.

Sheep, cattle, and goats

Perennial, evergreen shrub, climbing; leaves simple, whorled; leathery, margins entire, axillary glands at base; large showy, yellow or purple petal flowers; fruit is spiny capsule with numerous winged seeds.

The entire plant contains alkyliridoid-type terpinoids (allamandin, qallamandin, allamandacin), iridioids plumericin and plumieride, and little cardiotoxin. GI irritants in all parts (highest concentrations in the sap and roots). On ingestion, causes excess salivation, ruminal atony, abdominal cramps, diarrhea, dehydration, and electrolyte imbalance. Little cardiotoxic effects and no deaths. Lethal dose (fresh foliage) in cattle is 30 g/kg body wt.

Supportive, antidiarrheals

Cicuta spp

Water hemlock

Cicuta douglasii (Water hemlock)
Cicuta douglasii (Water hemlock), close-up
Cicuta douglasii (Water hemlock), tuber

Open, moist to wet environments; throughout North America


White flower, umbels. Veins of leaflets ending at notches. Stems hollow except at nodes. Tuberous roots from chambered rootstock.

Resinoids (cicutoxin, cicutol) in roots, stem base, young leaves. Toxicity retained when dry, except in hay. Rapid onset of clinical signs, with death in 15–30 min. Salivation, muscular twitching, dilated pupils. Violent convulsions, coma, death. Poisoning in people common.

Sedatives to control spasm and heart action. Prognosis good if alive 2 hr after ingestion.

Hymenoxys odorata


Hymenoxys odorata (Bitter rubberweed)

Roadways, lakebeds, flooded areas, overgrazed range; southwest

Sheep, rarely cattle

Multibranched annual or perennial up to 2 ft high. Yellow flower head. Leaves divided into narrow glandular segments.

Sesquiterpene lactone (hymenovin) in fresh or dry plant. Salivation, vomiting, green nasal discharge, depression, anorexia, abdominal pain. Lesions include inflammation of GI tract, foreign body pneumonia, renal degeneration.

Toxin cumulative. Avoid overgrazing. Remove from pasture.

Hymenoxys richardsonii

Pingue, Colorado rubber weed

Hymenoxys richardsonii (Colorado rubber weed)

Arid foothills (6,000–8,000 ft [1,800–2,400 m]); western

Sheep, cattle, goats

Perennial herb. Leaves bright green, divided into narrow glandular segments.

Same as for H odorata (above).

Same as for H odorata.

Oxalis spp, O corniculata (Oxalidaceae)

Wood sorrel, Creeping lady’s sorrel, Creeping yellow wood sorrel

Herb/ornamentals found as weeds, growing from rhizomes/bulbs in fields and/or grazing pasture; worldwide

Sheep, rarely cattle

Annual/perennial with palmately compound leaves with 3 leaflets on erect or ascending stem. Inflorescence cymes or umbel or solitary flower; fruits are capsules with many seeds and basal ariels.

High oxalate contents throughout. Acute, subacute, or chronic manifestation after chronic ingestion. Clinical signs—progression from depression, weakness, labored respiration to prostration, coma, and death in 1–2 days in acute cases. Chronic cases—weight loss, anorexia, polyuria, edema, increased BUN and creatinine levels, failure to concentrate urine, presence of oxalate crystals in urine sediments, and renal failure.

Parenteral calcium solution. Supportive care to allow for tubular regeneration.

Zephyranthes atamasco (Amaryllidaceae)

Atamasco lily, Rain lily, Zephyr lily, Easter lily

Ornamental, commonly grows from bulbs in low woods and wet meadow areas.

Horses, cattle, and indoor pets (cats)

Basal leaves with star-shaped white flowers turning pink on fading.

Phenanthridine (lycorine, tazettine) and other alkaloids primarily in the bulbs but also in the leaves and flowers. Anticholinergic-type effects (inhibitor of protein synthesis, decreases heart rate, and cardiac abnormalities) in cats. Vomiting, excess salivation, bloody diarrhea (dehydration and electrolyte imbalance), seizures, cardiac function changes, and dermatitis.

Prompt resolution of dermatologic signs with discontinued exposure. Supportive care—antiemetics, antidiarrheals, and electrolyte replacement. Rarely lethal.

Dangerous Season: Spring

Baptisia spp (Papilionoideae, Leguminosae, Fabaceae)

False indigo, Wild indigo, Rattle weed, Yellow indigo, Indigo weed

Open woods in Eastern North America on clay, loam, and sandy soils

Horses, cattle, goats

Herbaceous perennials, branched solitary stem, palmately compound sessile/short petiole, 3-leaflet leaves; terminal or axillary raceme inflorescence. Flowers with variably colored petals; legumes stipitate with one to many seeds. Plants black-gray or silvery gray when dry in the field or as hay.

Contains quinolizidine alkaloid cystisine, pyridine alkaloids anagyrine and baptifoline, and other related nicotine-like alkaloids. Interact with nicotinic, muscarinic, and acetylcholinergic receptors. On ingestion, causes severe diarrhea in cattle, decreased appetite, excess salivation, incoordination, and tremors. Fetal anomalies can be produced.

Remove animals from plant source. Symptomatic and supportive care.

Caesalpinia spp (Leguminosae)

Nikals, Grey nicker bean

Grown in the tropics in dry, open shrub or lowland rain forest. Found in southwestern USA. Ornamentals cultivated in warmer areas.

Cattle, sheep, probably horses

Perennial tree, shrub, or herb armed with thorns, erect or climbing stem, 2 pinnately compound leaves, terminal racemes, showy yellow to orange or red flowers, legumes ovate with 2 to many seeds.

Gallotannins (30%–50%), phytohemagglutinins in fruit and flowers and diterpenoids pulcherralpin and caesalpin in the leaves. Within a few hours of ingestion, animals show vomiting, ± bloody diarrhea, abdominal discomfort, and dehydration. Not reported to cause death.

Supportive care—IV fluids, electrolytes, antiemetics, and antidiarrheals.

Nolina texana

Sacahuista, Beargrass

Nolina texana (Sacahuista, Beargrass)

Open areas on rolling hills and slopes; southwest USA and Mexico

Cattle, sheep, goats

Perennial with many clustered, long narrow leaves. Stem mostly underground. Several flower stems with many small, white flowers in clusters.

Unidentified hepatotoxin (buds, flowers, fruit). Photosensitization, anorexia, icterus, prostration. Dark urine, yellowish discharge from eyes, nostrils. Lesions include hepatic and renal degeneration, GI inflammation.

Remove animals from area where plant grows during blooming season. Oral daily zinc oxide (not zinc sulfate) supplementation at 30 mg/kg body wt appears promising. ( See also Photosensitization Photosensitization .)

Peganum harmala

African rue

Peganum harmala (African rue)

Arid to semiarid ranges; western USA

Cattle, sheep, probably horses and camels

Multibranched, leafy, perennial, bright green, succulent herb. Leaves divided. Flowers white, single.

Related β-carboline indole alkaloids (seeds, leaves, stems; seeds more toxic). Anorexia, hindleg weakness, knuckling of fetlock, listlessness, excess salivation, subnormal temperature, pollakiuria. Lesions include gastroenteritis, with hemorrhages on heart and under liver capsule.

Unpalatable. Eaten only under drought conditions. General supportive care most helpful.

Phytolacca americana

Pokeweed, Poke

Phytolacca americana (Pokeweed, Poke)
Phytolacca americana (Pokeweed, Poke), close-up
Phytolacca americana (Pokeweed, Poke), flowering plant

Disturbed rich soils such as recent clearings, pastures, waste areas; eastern half of USA

Pigs, cattle, sheep, horses, people

Tall (to 9 ft), glabrous, green, red-purple, perennial herbs. Berries black-purple, staining, in drooping racemes.

Oxalic acid, a saponin (phytolaccatoxin), and an alkaloid (phytolaccin) in all parts; roots most toxic. Vomiting, abdominal pain, bloody diarrhea, hemolytic anemia, drop in production (dairy cattle). Terminal convulsions, death from respiratory failure. Lesions include ulcerative gastritis, mucosal hemorrhage, dark liver.

No specific remedy for intoxication. Supportive and symptomatic care helpful. Monitor for hypotension and other cardiac effects. Oils and protectants (GI tract). Dilute acetic acid PO, stimulants. Blood transfusion (hemolytic anemia).

Quercus spp


Quercus spp (Oak)

Most deciduous woods; throughout North America

All grazing animals, mostly cattle

Mostly deciduous trees, rarely shrubs, with 2–4 leaves clustered at tips of all twigs. Diverse leaf shape. Acorn fruiting body.

Gallotannin thought to be the toxin (young leaves and swollen or sprouting acorn). Anorexia, rumen stasis, constipation, followed by dark tarry diarrhea, dry muzzle, frequent urination, rapid weak pulse, death. Lesions include perirenal edema, nephrosis, gastroenteritis.

Diet must consist of >50% oak buds and young leaves for a period of time. Increased BUN with diet history diagnostic. Treatment symptomatic. Oral ruminatorics helpful. See also Quercus Poisoning Quercus Poisoning .

Sarcobatus vermiculatus

Greasewood, Black greasewood

Sarcobatus vermiculatus (Greasewood, black greasewood)

Alkaline or saline bottom soils, not in higher mountains; arid west. Dangerous season spring; may be year-round.

Sheep, cattle

Large deciduous shrub with spiny stems. Fleshy, alternate, round in cross-section. Flowers inconspicuous.

Oxalates (sodium and potassium) 10%–15% dry weight (leaves primarily, less so in stems and fruits). Dyspnea, weakness, depression, some salivation, atony of GI tract, coma, death (neurologic effects and renal failure). Hyperkalemia, hypocalcemia, increased BUN. Lesions include hemorrhage and edema of rumen wall, ascites, swollen kidneys (renal tubular necrosis and dilation).

Toxic when large quantity consumed in short time. Do not allow hungry animals to graze plant. Parenteral calcium solution offers temporary relief but relapses.

Xanthium spp


Xanthium strumarium (Cocklebur)
Xanthium strumarium (Cocklebur), dried specimen

Fields, waste places, exposed shores of ponds or rivers; throughout North America. Dangerous season spring and occasionally fall.

All animals, more common in pigs

Coarse annual herb. Fruit covered with spines, 2-beaked, with 2 compartments.

Carboxyatractyloside (seeds and young seedlings). Anorexia, depression, nausea, vomiting, weakness, rapid weak pulse, dyspnea, muscle spasms, convulsions. Lesions include GI inflammation, acute hepatitis, nephritis.

Seedlings or grain contaminated with seeds. Oils and fats PO may be beneficial; parenteral glucose and bicarbonate are reported helpful; warmth, stimulants IM.

Zygadenus spp

Death camas, Meadow death camas, Grassy death camas

Zigadenus venosa (meadow death camas, grassy death camas, death camas)

Foothill grazing lands, occasionally boggy grasslands, low open woods; throughout North and Central America

Sheep, cattle, horses

Perennial, bulbous, unbranched herbs with basal, flat, grass-like leaves. Flowers greenish, yellow, or pink; in racemes or panicles. No onion odor.

Cevanine-type veratrum azasteroid alkaloids, steroidal alkaloids, glycoalkaloids, and ester alkaloids (all parts). Salivation, vomiting, muscle weakness, ataxia or prostration, fast weak pulse, coma, death (central respiratory depression). No distinctive lesions.

Seeds most toxic. Leaves and stems lose toxicity as plant matures. Atropine sulfate and picrotoxin SC.

Dangerous Season: Spring and Summer

Aesculus spp


Aesculus spp (Buckeye)
Aesculus spp (Buckeye), plant with fruit

Woods and thickets; eastern USA and California

All grazing animals

Trees or shrubs. Leaves opposite and palmately compound. Seeds large, glossy brown, with large white scar.

Glycoside, aesculin; also alkaloids and saponins in all parts, especially seeds and leaves. Depression, incoordination, twitching, paralysis, inflammation of mucous membranes.

Young shoots and seeds especially poisonous. Treatment only in severe cases. Stimulants and purgatives. Prevent access to toxic plant. Recovery in days. Rarely fatal.

Amianthium muscaetoxicum

Fly poison, Staggergrass, Crow poison, Gray fly poison

Open woods, fields, and acid bogs; eastern USA

All grazing animals

Bulbous perennial herb. Leaves basal, linear. White flowers in a compact raceme, the pedicels subtended by short, brownish bracts.

Unidentified alkaloid, similar to those with Zygadenus (all parts). Salivation, vomiting, rapid and irregular respiration, weakness, death from respiratory failure.

No practical treatment. Especially dangerous for animals new to pasture. Keep animals well fed.

Delphinium spp


Delphinium occidentale (Tall larkspur)
Delphinium nelsonii (Low larkspur)

Either cultivated or wild, usually in open foothills or meadows and among aspen; mostly western USA. Dangerous season spring and summer, also seeds in fall.

All grazing animals, mostly cattle; sheep are somewhat resistant.

Annual or perennial erect herbs. Flowers each with 1 spur, in racemes. Perennial with tuberous roots. Leaves palmately lobed or divided.

Polycyclic diterpenoid alkaloids (eg, delphinine) in all parts, fresh or dry. Straddled stance, arched back, repeated falling, forelegs first. Constipation, bloat, salivation, vomiting. Death from respiratory and cardiac failure. Most often no lesions.

Young plants and seeds more toxic. Toxicity decreases with maturity. Antidote physostigmine rather than atropine.

Descurainia pinnata

Tansy mustard

Dense stands especially in wet years; arid southwest


Annual to 2 ft tall, stem and leaves covered with fine pubescence. Leaves alternate, deeply pinnately dissected. Inflorescence on elongated raceme. Flower small with 4 spreading yellow to yellow-green petals. Fruit is copula with 2 carpels and long waxy seeds in 2 rows.

Toxic principle unknown; must be grazed over relatively long period. Partial or complete blindness, inability to use tongue or swallow, “paralyzed tongue,” “blind staggers,” wandering, head pressing, emaciation, death if not treated.

Administer 2–3 gal. (8–12 L) water bid with stomach tube. Include nourishment if animal weak. Prognosis good if treatment started early. Possibly mustards cause same condition.

Lantana spp


Lantana spp (Lantana)

Ornamentals and wild; in lower coastal plain of southeast USA, and southern California

All grazing animals except horses

Shrubs. Young stems 4-angled. Leaves opposite. Flowers in flat-topped clusters, yellow, pink, orange, or red. Berries black.

Triterpenes (lantadene A and B) and unknowns in all parts, especially leaves and green berries. Anorexia, jaundice, watery feces, photosensitization. Lesions include degenerative changes in liver and kidneys. Death due to liver insufficiency, renal failure, myocardial damage.

Remove plants from pasture (herbicide 2,4-D susceptible). Keep animals out of light sources after eating plant.

Senna obtusifolia

Coffeepod, Sicklepod

Senna obtusifolia (Coffeepod, Sicklepod)
Senna obtusifolia (Coffeepod, Sicklepod), seeds

Found in cultivated (corn, soybean, or sorghum) and abandoned fields, along fences, roadsides; naturalized in eastern USA

Annual shrub frequently found in same fields as S occidentalis. Distinguishing features include leaflets fewer in number and more rounded. Seed pods long, round to 4-sided and more curved. Seeds shiny, brown, and rhomboid.

Toxic principles thought to be same as in S occidentalis. Clinical signs, although similar, less severe with S obtusifolia.

Treatment ineffective in down animals; salvaging most economic. Heat labile toxins not known to persist as residue. Meat from affected animals should be safe for human consumption.

Senna occidentalis

Coffee senna, Coffee weed, Styptic weed, Wild coffee

Senna occidentalis (Coffee senna, Coffee weed, Styptic weed, Wild coffee)
Senna occidentalis (Coffee senna, Coffee weed, Styptic weed, Wild coffee), seeds

Common along roadsides, waste areas and pastures; naturalized in eastern USA

Cattle, horses, chickens, goats, sheep, rabbits

Annual herb >3 ft tall, with glandular, alternate pinnately compound leaves (8–12 ovate to lanceolate leaflets, terminal pair largest). Flowers are yellow, axillary, solitary, or in short racemes. Long, flat, straight to slightly curved pods with clearly outlined seed contents. Of the pods, seeds, and wilted foliage, seeds are most toxic.

Anthraquinones (emodinglycosides and oxymethylanthraquinone), chrysarobin and lectin (toxalbumins), and alkaloids are associated with GI dysfunction and myodegeneration. Afebrile, ataxic, with diarrhea and coffee-color urine, recumbent but eat and are alert shortly before death. Increased serum CK and isocitric dehydrogenase activities; hyperkalemia and myoglobinuria frequent. Lesions include cardiac and skeletal muscle degeneration. Congestion, fatty degeneration, and centrilobular necrosis (liver) in addition to tubular degeneration (kidneys) also reported. Death probably due to hyperkalemic heart failure.

No specific treatment known. Symptomatic and supportive care essential. Although gross lesions similar to those of vitamin E/selenium deficiency, this therapy is contraindicated. Mineralocorticoid therapy may facilitate potassium excretion. Remove animals from source. Salvaging for economic reasons (see Senna obtusifolia, above).

Tetradymia spp


Tetradymia canescens (Spineless horsebrush)
Tetradymia glabrata (Little leaf horsebrush)

Arid foothills and higher desert and sagebrush ranges, dense stands along trails; western USA


Shrubs with yellow flowers in spring, not later. Leaves spiny, silvery white. Early deciduous.

Furanoeremophilanes (tetradymol and others). Photosensitization, “bighead,” loss of hair and wool, skin ulcerations, blindness, secondary infections. Lesions include dermal necrosis and edema, hepatic and renal degeneration. Abortions may occur.

Photosensitization seen with concurrent ingestion of other green forages. Remove animals from plant source and sunlight. Antihistamines, topical antibiotics, and parenteral corticosteroids beneficial. Recovery slow and possibly incomplete.

Veratrum spp

False hellebore, Skunk cabbage

Veratrum californicum (False hellebore)

Low, moist woods and pastures, and high mountain valleys; western USA

Sheep, cattle

Erect herbs. Leafy throughout, leaves large and plaited. Flowers small and white or greenish.

Steroidal alkaloids. Vomiting, excess salivation, cardiac arrhythmia, bradycardia, dyspnea, muscle weakness and paralysis, coma, congenital cyclops in lambs from ewes exposed to V californicum.

Respiratory and heart stimulants.

Dangerous Season: Summer and Fall

Acer rubrum

Red maple

Acer rubrum (red maple), young plant

Moist land and swamps; eastern


A large tree at maturity. Leaves opposite, 2–6 in. across, palmately 3- or 5-lobed each, roughly triangular, and coarsely toothed. Red to yellow polygamous flowers. Fruit, a pair of 1-seeded winged units connected at base.

Unknown toxic principle(s) in wilted leaves. Methemoglobinemia, Heinz body anemia, and intravascular hemolysis; weakness, polypnea, tachycardia, depression, icterus, cyanosis, brownish discoloration of blood and urine.

Not common. Methemoglobinemia a prognostic indicator. Isotonic fluids, oxygen, and blood transfusion can be helpful. Methylene blue therapy not rewarding. Early ascorbic acid treatment essential for recovery.

Apocynum spp


Apocynum cannabinum (Hemp dogbane)
Apocynum spp, fruit (pods)

Open woods, roadsides, fields; throughout North America


Erect, branching, perennial herb with milky sap arising from creeping underground root stock. Leaves opposite. Flowers white to greenish white in terminal clusters. Fruit long, slender, paired, with silky-haired seeds.

A resinoid and glucoside with some cardioactivity found in leaves and stems of green or dry plants. Increased temperature and pulse, dilated pupils, anorexia, discolored mucous membranes, cold extremities, death.

Symptomatic (cardiotoxin) IV fluids and gastric protectants suggested.

Centaurea repens

Russian knapweed

Centaurea repens (Russian knapweed)

Waste areas, roadsides, railroads, and overgrazed rangeland; not common in cultivated or irrigated pastures; mostly western and upper midwestern USA


Perennial weed with slender rhizomes. Stems erect and well branched. Leaves pinnately lobed to entire, not spiny, narrowed basally but not petioled and of decreasing length up the plant. Thinly pubescent or glabrous. Blue, pink, or white flowers. One-seeded fruit with whitish, slightly ridged attachment scar.

Unidentified alkaloid in fresh or dried plant. Chronic exposure, acute onset of signs. Inability to eat or drink, facial dystonia, chewing, yawning, standing with head down, severe facial edema, 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 C solstitialis (below) but with similar pathology and prognosis. Some relief with massive doses of atropine but not an effective treatment. Euthanasia recommended.

Centaurea solstitialis

Yellow star thistle, Yellow knapweed

Centaurea solstitialis (Yellow star thistle, Yellow knapweed)

Waste areas, roadsides, pastures; mostly western


Annual weed. Leaves densely covered with cottony hair. Terminal spreading cluster of bright yellow flowers with spines below. Branches winged.

Unidentified alkaloid. 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. Liquefactive necrosis of substantia nigra and globus pallidus (brain) pathognomonic. No treatment. Euthanasia recommended.

Eupatorium rugosum

White snakeroot

Eupatorium rugosum (White snakeroot)

Woods, cleared areas, waste places, usually the moister and richer soils; eastern USA

Sheep, cattle, horses

Erect perennial herb. Tremetol leaves, opposite, simple, serrated. Flowers small, white, and many. Often grows in large patches.

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 1–3 days.

“Milk sickness” or “trembles.” Treatment nonspecific and symptomatic. Heart and respiratory stimulants and laxative may be necessary. Remove animal from access to plant, discard milk (hazardous to people).

Hypochaeris radicata

Flatweed, Cat’s-ear, Gosmore

Native to the Mediterranean and South America; widely distributed in the USA—Pacific states, eastern/southeastern USA


Perennial herb with viscid sap, stemless. Simple, serrated to lobed, basal, alternate leaves. One to several bright yellow flowers per plant.

Unknown; associated with but not proven cause of a neurologic condition in horses—stringhalt (hypermetria/hyperflexion of pelvic limb) in dry years. Sudden onset of abnormal gait; flexion/delayed extension of hocks, knuckling of carpal joints, laryngeal hemiplasia; spontaneous 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 (pelvic tenotomy of the lateral digital extensors) reported helpful.

Oxytenia acerosa, Iva acerosa


Oxytenia acerosa (Copperweed)
Oxytenia acerosa (Copperweed), flowering plant

Arid, alkaline soils in foothills, sagebrush plains; western USA

Cattle, sheep

Tall, annual/perennial herb with narrow leaflets. Flowers in many heads resembling goldenrod.

Unknown (pseudoguaianolide sesquiterpene lactones found in species–-consistent clinical signs with these toxins); all above-ground parts, green or dry. Metabolic disease, anorexia, marked depression, weakness, coma; death without struggle within 1–3 days.

No specific treatment. Supplement diet or change pasture.

Perilla frutescens

Perilla mint, Beefsteak plant

Perilla frutescens (Perilla mint, Beefsteak plant)

Ornamental originally from India, escaped to moist pastures, fields, roadsides, and waste places; southeastern USA

Cattle primarily, horses and other livestock susceptible

Annual, freely branched, squared stems. Opposite, purple or green, coarsely serrated leaves. White to purple flowers. Strong pungent odor when crushed.

Green or dry, 3-substituted furans (perilla ketone, egomaketone, isoegomaketone). Signs 2–10 days after exposure include dyspnea (especially on exhaling), open-mouth breathing, lowered head, reluctance to move, death on exertion. Lesions include pulmonary emphysema and edema.

Treatment ineffective once clinical signs severe. Parenteral steroids, antihistamines, and antibiotics may help. Handle gently (prevents exertion and death). Avoid/limit grazing during flowering and fruiting period.

Prosopis glandulosa


Dry ranges, washes, draws; southwest

Primarily cattle, also goats; sheep resistant

Perennials, deciduous shrub or small tree with smooth or furrowed gray bark, paired spines. Leaves divided. Legume pod long, constricted between seeds.

Unknown principle in the beans. Chronic wasting with rumen atony, excess salivation, continual chewing. Partial paralysis of tongue, facial muscle tremor, submandibular edema, anemia. Lesions include emaciation, small firm kidneys and liver, gastroenteritis, filled rumen.

High sucrose content of beans alters rumen microflora, inhibiting cellulose digestion and B vitamin synthesis if grazed for extended period.

Robinia pseudoacacia

Black locust, False acacia, Locust tree

Robinia pseudoacacia (Black locust, False acacia, Locust tree)
Robinia pseudoacacia (Black locust, False acacia, Locust tree), branch

Open woods, roadsides, pinelands, on clay soils preferably; eastern USA

All grazing animals, mostly horses

Tree or shrub. Deciduous, alternate, pinnately compound (>10 elliptic to ovate leaflets) leaves. Pair of spines at base of each leaf. Flowers in loose, fragrant, white to cream, drooping racemes. Flattened, brown pods containing 4–8 seeds.

The glycoside robitin, a lectin (hemagglutinin), and the phytotoxins robin and phasin found throughout plant, although flowers have been suggested as the toxic principles. Diarrhea, anorexia, weakness, posterior paralysis, depression, mydriasis, cold extremities; frequently laminitis and weak pulse. Death infrequent; recovery period extensive. Postmortem lesions restricted to GI tract.

Laxatives and stimulants suggested. Treatment symptomatic.

Rumex crispus

Curly dock, Dock, Sorrel

Rumex crispus (Curly dock, Dock, Sorrel)

Commonly found on acid or sterile, graveled, seasonally moist soils of waste places, pastures, and fields throughout USA

Cattle, sheep

Perennial herb with erect stems, 3–4 ft tall. Leaves alternate, lanceolate to elliptic, finely crisped margins, base obtuse to cuneate, petioles form sheath around stem. Flowers small, numerous, greenish, in long terminal panicles; fruit an achene, papery 3-winged, with lustrous brown seeds.

Oxalic acid and soluble oxalate in leaves, stem, and seeds. Acute course (hypocalcemia, labored breathing, anorexia, depression, muscle fasciculation, tremor, weakness, teeth grinding, pulmonary edema, tetany, seizure, recumbency, and prostration); subacute (hypocalcemia, altered kidney function) or chronic course (renal fibrosis, renal insufficiency, and urolithiasis). Hemorrhage, edema (rumen and abomasal walls), and ascites (intestinal mucosa) seen in toxic cases. Death resulting from shock and hemorrhagic rumenitis.

In acute cases, death is too rapid for any treatment. Symptomatic and supportive care can be helpful. Remove animals from source. Calcium IV to correct hypocalcemia is ineffective. Give lime water to precipitate oxalate and prevent absorption. Allow animals to develop tolerance to oxalate by exposure to small amounts over time. Do not allow animals to graze pasture or offer hay highly contaminated with oxalate-producing plants.

Solanum spp

Nightshades, Jerusalem cherry, Potato, Horse nettle, Buffalo bur

Solanum nigra (Black nightshade)
Solanum nigra (Black nightshade), with berries
Solanum tuberosum (Potato)
Solanum carolinense (Horse nettle)
Solanum rostratum (Buffalo burr), young plant
Solanum rostratum (Buffalo burr), flowering plant

Fence rows, waste areas, grain and hay fields; throughout North America


Fruits small; yellow, red, or black when ripe; structurally like tomatoes; clustered on stalk arising from stem between leaves.

Glycoalkaloid solanine (leaves, shoots, unripe berries). Acute hemorrhagic gastroenteritis, weakness, excess salivation, dyspnea, trembling, progressive paralysis, prostration, death.

Pilocarpine, physostigmine, GI protectants. Seeds may contaminate grain.

Dangerous Season: Fall and Winter

Allium cepa, A canadense

Onions (cultivated and wild)

Allium spp (Cultivated onion)
Allium spp (Wild onion)

Cultivated and grown on rich soils throughout USA

Cattle, horses, sheep, dogs

Biennials and perennials, bulb plants, onion odor. Leaves basal, green, hollow, cylindrical (A cepa), lustrous green, flat (A canadense); flowers on hollow flowering stalks, terminal umbels of many small blooms; fruits 3-celled capsules with many seeds.

N-propyl disulfide, an oxidant, in all parts. Anemia develops within days of exposure. Toxicosis in cattle associated with prolonged ingestion of large amounts of onions. N-propyl disulfide inhibits RBC glucose-6-phosphate dehydrogenase, leading to hemolysis and formation of Heinz bodies. Clinical signs are hemoglobinuria, diarrhea, loss of appetite, jaundice, ataxia, collapse, and possible death if untreated. Hemolytic anemia reported in livestock ingesting wild onions. Heinz body anemia; swollen, pale, necrotic liver; hemosiderin in liver, kidneys, and spleen are reported pathologic lesions.

Clinical signs similar to toxicity induced by S-methylcysteine sulfoxide (a rare toxic amino acid in Brassica spp) 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.

Astrolepis sinuata cochisensis

Jimmy fern, Cloak fern

Dry rocky slopes and crevices, chiefly limestone areas; southwest

Sheep, goats, cattle

Evergreen from rhizomes, perennial, erect fern with divided leaves, folding when dry. Leaflets about as wide as long, scaly on back.

Unknown (excreted in milk). Nervous syndrome, incoordination, arched back, trembling, increased respiratory rate and pulse. Death when not allowed to rest.

No specific treatment. Supportive and general nursing care helps. Avoid driving during danger period. Provide ample watering, placed to avoid long walks. Allow rest if signs occur.

Daubentonia punicea

Rattlebox, Purple sesbane

Daubentonia (Sesbania) punicea (Rattlebox, Purple sesbane)

Cultivated and escaped, in waste places; southeastern USA coastal plain


Annuals or perennials, shrub. Leaves pinnately compound with ≥20 leaflets. Flowers orange-red, rose, or purple. Legume pods (≥5 seeds) longitudinally 4-winged.

S punicea most toxic species (0.1% body wt toxic to sheep and cattle). Toxin(s) not fully characterized, but saponins are primary suspects; 12–24 hr delay in clinical signs after ingestion. Rapid pulse, weak respiration, diarrhea, death.

Symptomatic treatment; specific cause unknown. Seeds poisonous. Remove animal from source. Fluids and electrolytes for dehydration.

Glottidium vesicarium

Bladderpod, Rattlebox, Sesbane, Coffeebean

Glottidium (Sesbania) vesicarium (Bladderpod, Rattlebox, Sesbane, Coffeebean)

Glottidium (Sesbania) vesicarium (Bladderpod, Rattlebox, Sesbane, Coffeebean), flowering plant

Mostly open, low ground, abandoned cultivated fields; southeastern USA coastal plain


Tall annual. Legume pods flat, tapered at both ends, 2-seeded. Leaves pinnate, divided. Flowers yellow.

Unknown (green plant and seeds). In ruminants, hemorrhagic diarrhea, shallow rapid respiration, fast irregular pulse, coma, death. Lesions include hemorrhages in abomasum and intestines, dark tarry blood.

Green seeds are more toxic. Remove animal from source immediately. Symptomatic, general supportive treatment—saline purgatives, rumen stimulants, IV fluids.

Halogeton glomeratus


Halogeton glomeratus (Halogeton)
Halogeton glomeratus (Halogeton), flowering plant

Deserts, overgrazed areas, winter ranges, alkaline soils; western USA

Sheep, cattle

Annual herb. Leaves fleshy, round in cross-section, tip with stiff hair. Axillary flowers inconspicuous. Fruits bracted and conspicuous.

Oxalic acid, oxalate. Acute course. Rapid labored respiration, depression, weakness, coma, death. Lesions include hemorrhages and edema of rumen wall, swollen kidneys, oxalate crystals in kidneys and rumen wall.

Toxic dose consumed over short period. Increase water consumption. Standard therapy IV calcium borogluconate (helpful in cattle, delay deaths in sheep). Calcium supplement (83% alfalfa, 15% calcium carbonate, 2% molasses) in feed before grazing. Halogeton forage can be helpful. Herbicide 2,4-D control.

Isocoma pluriflora (Haplopappus heterophyllus)

Rayless goldenrod, Burroweed, Jimmyweed

Isocoma pluriflora (Haplopappus heterophyllus) (Rayless goldenrod, jimmyweed)

Dry plains, grasslands, open woodlands, and along irrigation canals; alkaline soils; southwestern USA and northern Mexico

Cattle, sheep, horses

Bushy perennial 2–4 ft tall, with many yellow flowerheads. Leaves alternate, linear, sticky.

Complex benzyl alcohol (tremetol); resin acid; primarily nursing young and nonlactating animals. Reluctance to move, trembling, weakness, vomiting, dyspnea, constipation, prostration, coma, death.

“Milk sickness.” Similar treatment to E rugosum intoxication. Prevent access to plants (growing season). Remove young and discard milk (hazardous to people).

Juglans nigra

Black walnut

Juglans nigra (Black walnut)
Juglans nigra (Black walnut), leaves and fruit
Juglans nigra (Black walnut), shavings

Native to eastern USA; now from eastern seacoast, west to Michigan and most of the Midwest, south to Georgia and Texas


Tree with deciduous, alternate, pinnately compound leaves (numerous lanceolate leaflets with serrated margins); leaflets in middle are largest. Male and female flowers on same tree but different inflorescences. Thick husked nut does not open when ripe. Twigs have chambered pith.

Juglone, phenolic derivative of naphthoquinone. Shavings with as little as 20% black walnut toxic within 24 hr of exposure. Reluctance to move; depression; increased temperature, pulse, respiration rate, abdominal sounds, digital pulse, hoof temperature; distal limb edema; lameness. Severe laminitis with continued exposure.

Nonfatal; laminitis and edema of lower limbs. Remove shavings promptly (relief signs). Treat for limb edema and laminitis. Improvement in 24–48 hr with no sequelae. NSAIDs are mainstay; prazosin, nifedipine are promising. Avoid corticosteroids (worsen existing vasoconstriction).

Melilotus officinalis and M alba

Sweet clover, White sweet clover

Melilotus officinalis (Sweet clover)

Commonly found on alkaline soils, fields, roadsides, and waste places; forage crop in southern and northern USA

Most commonly cattle, also horses and sheep

Annual or biennial herb 3–6 ft tall. Leaves alternate, pinnately compound with 3 obovate leaflets, serrated margins. Yellow or white flowers on racemes. Small 1-seeded pods.

Sophora secundiflora

Mescal bean, Coral bean, Sophora, Frijolito, Texas mountain laurel

Hills and canyons, limestone soils; southwestern Texas into Mexico

Cattle, sheep, goats

Evergreen shrub or small tree. Leaves alternate, divided, and leathery. Flowers violet-blue, fragrant. Seeds large and bright red with hard seed coat, in legume pod.

Quinolizidine alkaloid (seeds and probably leaves). Violent trembling, stiff gait, falling on exercise, recumbent for a few minutes, becoming alert and eating.

Symptomatic. Toxic effect not cumulative, consume large amounts quickly. Seeds more dangerous when crushed.

Dangerous Season: Fall, Winter, and Spring

Melia azedarach


Melia azedarach (Chinaberry), young plant
Melia azedarach (Chinaberry), mature plant with berries
Melia azedarach (Chinaberry), berries

Fence rows, brush, waste places; southern USA

Pigs and sheep, others (dogs) less susceptible

Small to medium deciduous tree. Fruit cream or yellow with a furrowed globose stone, persisting on tree through winter. Large amount required for intoxication.

Several alkaloids and a saponin (all parts), fruit most toxic. Restlessness, vomiting, constipation, cyanosis, rapid pulse, dyspnea, death within 24 hr.

Gastroenteritis usual. Recovery may be spontaneous. Laxatives and GI protectants suggested.

Dangerous Season: All Seasons

Acacia berlandieri

Guajillo, Catclaw, Blackbrush, Acacia

Semiarid rangelands; southwestern Texas into Mexico

Sheep, goats

Deciduous shrub or small tree. Leaf divided. Flowers white to yellowish in dense heads. Fruit a legume with margins thickened.

Amine, N-methyl-β-phenylethylamine. Chronic course. Ataxia of hindquarters (limberleg), marked excitation, prostration, remain alert, death from starvation.

Dominates vegetation in some areas. Valuable to sheep industry due to high nutritive value and dominance. Supplement during drought to reduce possibility of poisoning.

Agave lechuguilla


Agave spp (Lecheguilla)
Agave spp (Lecheguilla), close-up

Low limestone hills, dry valleys, and canyons; southwest. Dangerous all seasons, especially spring.

Sheep, goats, cattle, usually during drought

Perennial, stemless, with thick, fleshy, tapered leaves having sharply serrated margins. Flowers infrequently with tall terminal panicle.

Unidentified hepatotoxin (causing photosensitivity) and a toxic saponin (abortifacient action). Subacute course. Listlessness, anorexia, icterus, yellow discharge from eyes and nostrils, photosensitization, coma, death.

Remove animals from range and provide shade. See Photosensitization Photosensitization .

Agrostemma githago

Corn cockle

Agrostemma githago (Corn cockle)
Agrostemma githago (Corn cockle), close-up

Weed, grainfields, and waste areas; throughout North America


Green winter annual with silky-white hairs, opposite leaves, purple flowers, black seeds.

Saponin (githagenin) in seeds. Acute course. Profuse watery diarrhea, vomiting, dullness, general weakness, tachypnea, hemoglobinuria, death.

Maintain hydration (fluids and electrolytes) and control diarrhea. Oils and GI protectants. Neutralize toxin (dilute acetic acid PO). Blood transfusions may be necessary.

Asclepias spp


Asclepias labriformias (Labriform milkweed)
Asclepias subverticulatus (Whorled milkweed)

Dry areas, usually waste places, roadsides, streambeds, western USA


Perennial erect herbs, shrubs, vines, or small trees with milky sap. Leaves simple, opposite/whorled with entire margins. Seeds silky-hairy from elongated pods.

Steroid glycosides and toxic resinous substances (all parts), green or dry. Staggering, tetanic convulsions, bloating, dyspnea, dilated pupils, rapid and weak pulse, coma, death.

Sedatives, laxatives, and IV fluids suggested. Prevent plant consumption. Do not feed milkweed-contaminated hay.

Astragalus spp, Oxytropis spp (certain species only)


Oxytropis sericea (White point locoweed)

Mostly western

All grazing animals

Stemmed or stemless perennial herbs. Leaves alternate and pinnately compound. Flowers leguminous. Chronic intoxication.

Swainsonine. Depression, emaciation, incoordination, dry lusterless hair. Abortions. Neurovisceral cytoplasmic vacuolation, congestive right heart failure in cattle grazing at high altitudes.

Avoid grazing of source. Both green and dry plants toxic.

Astragalus spp (certain species only)

Milk vetch, etc (many common names)

Astragalus spp (Timber milkvetch)

Nearly all

All grazing animals

As above.

Miserotoxin, other aliphatic nitro compounds. Posterior paralysis, goose-stepping, depression, rough coat, pulmonary emphysema, acute death, cord demyelination.

Avoid grazing of preflower stage.

Astragalus spp (certain species only— selenium accumulators)

Many common names

Astragalus spp (Two groove milkvetch)
Astragalus spp (Red stemmed peavine)

Seleniferous areas, mostly western and midwestern

All grazing animals

As above.

Selenium (chronic). Slow growth, reproductive failure, loss of hair, sore feet, acute death.

Avoid grazing seleniferous plants for extended periods. See Selenium Toxicosis Selenium Toxicosis .

Baccharis spp

Silverling, Baccharis, Yerba-de-pasmo

Baccharis spp (Silverling, Baccharis, Yerba-de-pasmo)
Baccharis spp (Silverling, Baccharis, Yerba-de-pasmo), young plant

Open areas, often moist; southeastern and southwestern USA


Shrubs. Numerous small, whitish flowers. Leaves resin-dotted and persistent southward.

Unidentified. Acute course. Rumen stasis, bloat, anorexia, excess salivation, diarrhea, staggering, trembling, restlessness, polypnea, tachycardia, death.

Most dangerous in early growing stage. Toxin concentrated in leaves and flowers. No specific treatment. Treatment toward relief of diarrhea is best.

Brassica spp, Raphanus spp, Descurainia spp, Berteroa incana

Mustards, Crucifers, Cress; and for B incana, Hoary alyssum, Hoary false alyssum

Fields, waste areas, hay meadows, roadsides; throughout North America

Cattle, horses, pigs

Annuals/biennials herbaceous weeds with terminal clusters of yellowish flowers and slender, elongated seed pods.

Glucosinolates (isothiocyanate, thiocyanates, nitrites) in seeds and vegetative parts, fresh or dry. Acute/chronic course. Anorexia, severe gastroenteritis, salivation, diarrhea, paralysis, photosensitization, hemoglobinuria. Unknown toxin(s) in B incana cause rapid onset of transient distal limb edema, laminitis (horses), and severe GI disturbances with continued exposure. Late abortions and/or weak, premature foals at birth.

No specific treatment (B incana disease in horses). Phenylbutazone, flunixin, furosemide or other diuretics helpful in relieving pain, inflammation, and edema. Remove from source. Administer GI protectants (mineral oil).

Cestrum diurnum, C nocturnum

Day-blooming jessamine and night-blooming jessamine, respectively

Cestrum diurnum, (Day-blooming jessamine)

Open woods and fields; Gulf Coast states (Florida, Texas) and California

Cattle, horses, and dogs (ingesting cholecalciferol-based rodenticides)

Evergreen shrubs or tall bush; leaves alternate, ovate smooth-edged; flowers white, tubular, small clusters, fragrant by day; fruit, a greenish-white to lavender (immature), becoming dark purple to black (mature), fleshy berry, with several small, black, oblong seeds, dispersed by birds in droppings. Leaves longer, night fragrant flowers, white fruits at maturity (C nocturnum).

Atropine-like alkaloids (fruit), saponins (fruit and sap), and glycosides of 1,25-dihydroxycholecalciferol (leaves primarily, stem, fruits, and roots) are found. Gastroenteritis develops on ingestion of fruits. Vomiting, depression, anorexia, chronic weight loss with normal appetite, choppy stiff gait, increased pulse, persistent hypercalcemia and hyperphosphatemia, calcinosis (aorta, carotid and pulmonary arteries, tendons, ligaments, and kidneys). Parathyroid atrophy, thyroid (C-cell) hypertrophy, and osteopetrosis reported with chronic ingestion of leaves.

Prevent further access of animals to plants. In early stages, treatment might be effective and cost-effective. Correct fluid and electrolyte imbalances in cases with persistent vomiting or diarrhea. Reduce or prevent hypercalcemia (calciuresis, diuretics, steroids, calcitonin). Maintenance therapy of diuretics and steroids may be necessary.

Conium maculatum

Poison hemlock

Conium maculatum (Poison hemlock)
Conium maculatum (Poison hemlock), leaves and flowers

Roadside ditches, damp waste areas; throughout North America


Purple-spotted hollow stem. Leaves resemble parsley, parsnip odor when crushed. Taproot. Flowers white, in umbels.

Piperidine alkaloids (coniine and others) in vegetative parts. Acute course. Dilated pupils; weakness; staggering gait; slow pulse, progressing to rapid and thready. Slow, irregular breathing; death from respiratory failure. Teratogenic in cattle.

Coniine excreted via lungs and kidneys, mousy odor of breath and urine diagnostic. Administer saline cathartics; neutralize alkaloids with tannic acid, together with stimulants.

Crotalaria spp

Crotalaria, Rattlebox

Crotalaria spp (Crotalaria, Rattlebox, Rattleweed)

Fields and roadsides; eastern and central USA


Annual or perennial legume. Yellow flowers in racemes, pods inflated. Bracts at base of pedicels of flowers and fruits persistent. Leaves simple or divided. Seeds in harvested grain.

Pyrrolizidine alkaloid (monocrotaline) and other unidentified alkaloids (all parts, especially seeds). Chronic course. Chickens—diarrhea, pale comb, ruffled feathers; horses—unthriftiness, ataxic, walking in circles, icterus; cattle—bloody diarrhea, icterus, rough coat, edema, weakness. Death may occur from a few weeks to months after ingestion.

Cumulative, fresh or dry. No treatment.

Cynoglossum officinale

Hound’s tongue

Cynoglossum officinale (Hound's tongue)

Common in waste places, roadsides, and pastured areas throughout USA

Cattle, sheep, horses

Annual or biennial herbaceous plant, rough hairy stem and foliage, 3–4 ft tall. Leaves alternate, oblanceolate, narrowed to petiole (lower), lanceolate, sessile, clasping (upper). Flowers numerous in coiled racemes, without bracts, blue, purple, or white blooms. Fruit, burr-like from 4 nutlets, thickly covered with hooked prickles.

Pyrrolizidine alkaloids (0.6%–2.1% of dry matter) including heliosupine and echinatine in the foliage. Unpleasant odor discourages consumption when fresh, becomes palatable in hay and is readily consumed. Toxic insult primarily hepatic and chronic in nature. Pyrrolizidine alkaloids (inactive) undergo hepatic metabolization to active intermediates—pyrroles (alkylating agent), which are toxic. Clinical signs are anorexia, depression, rough hair coat, hemorrhage, tenesmus, bloody feces, ataxia, jaundice, death. Hepatic lesions of necrosis, edema, megalocytosis, bile duct hyperplasia, and cytoplasmic vacuolation reported.

Know source and quality of hay. Treatment symptomatic and supportive at best. Affected animals seldom recover.

Datura stramonium

Jimson weed, Thorn apple

Datura stramonium (Jimson weed, Thorn apple), young plant
Datura stramonium (Jimson weed, Thorn apple), fruiting body
Datura stramonium

Fields, barn lots, trampled pastures, and waste places on rich bottom soils; throughout North America


Leaves wavy. Flower large (4 in.), white, tubular. Fruit a spiny pod, 2 in. (5 cm) long.

Tropane alkaloids (atropine, scopolamine, hyoscyamine) in all parts, seeds in particular. Acute 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 (physostigmine, pilocarpine, arecoline).

Drymaria pachyphylla

Inkweed, Thickleaf drymary

Heavy alkaline clay soil in low areas or dry, overgrazed pastures; southwestern USA

Cattle, sheep, goats

Multibranched, succulent, prostrate annual. Opposite or whorled appearing leaves. Small white flowers.

Problem in heavily overgrazed areas. Unknown toxin. Sudden onset of diarrhea, restlessness, depression, coma, death. Lesions include gastroenteritis with congestion of liver, kidneys, spleen. Petechial hemorrhages on heart.

Dangerous during drought, after rain, or at night. Avoid overstocking to improve range. In well-fed and watered animals, little or no problem observed. Poor response to treatment.

Festuca arundinacea

Tall fescue

Festuca arundinacea (Tall fescue)

A coarse, hardy, drought-resistant grass; Pacific Northwest, Missouri, Oklahoma, and Kentucky; major pasture grass in southeastern USA

Mostly cattle and horses

Coarse, deeply rooted perennial grass. Broad, dark-green, ribbed, rough upper surface, and smooth sheathed leaves. Grows in clumps.

Gelsemium sempervirens, G rankinii

Yellow jessamine, Evening trumpet flower, Carolina jessamine

Gelsemium sempervirens (Yellow jessamine, Evening trumpet flower, Carolina jessamine), flowering vine

Open woods, thickets, swamps, low areas, and open fields; southeastern USA


Climbing or trailing vines. Evergreen, entire, opposite leaves. Yellow tubular flowers, very fragrant.

Potent neurotoxic alkaloids (gelsemine and others, related to strychnine) in all parts. Gelsemine the most toxic. Acute course. Weakness, incoordination, dilated pupils, convulsions, coma, death within 48 hr. Limberneck in fowl. Clinical signs indicative of a poor prognosis.

No specific treatment. Relaxants and sedatives suggested. PO administration of strong tea/coffee or poison hemlock suggested on early exposure (before observation of clinical signs) seems helpful in reducing further toxin absorption (more basic stomach pH).

Gutierrezia microcephala

Threadleaf, Snakeweed, Small-head matchweed, Sticky snakeweed

Widespread over dry range and desert; primarily southwestern USA

Cattle, sheep, goats, pigs

Multibranched, perennial (toxicologically significant), resinous shrub. Simple leaves, alternate; yellow-flowered heads.

Unknown. Steroidal effect of saponins, mono- and diterpene acids. Acute poisoning, anorexia, listlessness, hematuria, diarrhea followed by constipation. In cattle, abortions with retained placenta, stillbirths, or premature and weak calves.

No specific treatment. Supplementing diet will help but not entirely prevent abortion in cattle.

Helenium hoopesii

Orange sneezeweed

Helenium hoopesii (Sneezeweed)

Moist slopes and well-drained mountain meadows; abundant in overgrazed areas; western USA

Sheep, rarely cattle

Annuals, biennials, perennial herb. Orange sunflower-like heads or yellow flowers. Leaves alternate.

Sesquiterpene lactones (helenalin, hymenoxin). Subacute course (spewing sickness). Depression, weakness, restlessness, stiff gait, salivation, pronounced vomiting, emaciation, eventual death.

Cumulative. Aspiration pneumonia frequent. Remove from access to plant. Graze sneezeweed areas for only short periods of time. Can graze intermittently with some success.

Helenium microcephalum

Small head sneezeweed

Moist ground; southern USA

Cattle, sheep, goats

Annual, erect herb, simple-stemmed below, bushy above. Stem winged. Narrow leaves throughout. Flowers in small heads; disk pale red-brown, rays yellow.

Sesquiterpene lactone (helenalin) in flowering stage. Depression, weakness, restlessness, stiff gait, salivation, vomiting.

Cumulative. Remove from pasture. Cathartics may help.

Hypericum perforatum

St. John’s-wort, Goatweed, Klamath weed

Hypericum perforatum (St. John's-wort, Goatweed, Klamath weed)

Dry soil, roadsides, pastures, ranges; throughout North America

Sheep, cattle, horses, goats

Perennial herb or woody below. Leaves simple, opposite or whorled, dotted. Flowers many, yellow, with many stamens.

Photodynamic pigment (hypericin). Subacute course. Photosensitization, pruritus and erythema, blindness, convulsions, diarrhea, hypersensitivity to cold water contact, death.

Remove animals from source and sunlight. Corticosteroids parenterally, topical broad-spectrum antibiotics.

Kalmia spp

Laurel, Ivybush, Lambkill

Kalmia spp (Laurel, Ivybush, Lambkill)

Rich moist woods, meadows, or acid bogs; eastern and northwestern. Dangerous all seasons, especially winter and spring.

All, often sheep

Woody shrub. Evergreen, glossy leaves. Flowers pink to rose, showy.

Resinoid (andromedotoxin) and a glucoside (arbutin) in vegetative parts. Acute course. Incoordination, excess salivation, vomiting, bloat, weakness, muscular spasms, coma, death.

Undigested rumen contents and ingesta in lungs at necropsy. Laxatives, demulcents, nerve stimulants, atropine.

Kochia scoparia

Kochia, Burning bush, Fireball, Fireweed, Poor man’s alfalfa

Kochia scoparia (Kochia)
Kochia scoparia (Kochia), seedling

Throughout North America

Cattle, sheep

Annual to 5 ft tall. Many branched stems give bushy appearance. Leaves petiolate, lanceolate, thin, and flat; alternate. Fruit has 5 wedge-shaped wings.

An alkaloid has been suggested. This plant may also accumulate nitrate and oxalate. Disease syndromes: photosensitization, weight loss, and polioencephalomalacia, which seems intensified by slow growth and sulfates.

Harvested foliage is source of toxin. Protect from sun in case of photosensitization; treat polioencephalomalacia with vitamin B. Supplement with copper (preventive against polioencephalomalacia).

Ligustrum spp

Privet, Ligustrum, Hedge plant

Ligustrum spp (Privet, Ligustrum, Hedge plant)

An ornamental; common as hedge; found at abandoned farm home sites, along fences, and in bottomlands; eastern USA

All livestock

Shrubs up to 15 ft tall. Simple, opposite, short-petioled, evergreen or deciduous leaves. Numerous small, white flowers in panicles. Fruit is 1- to 2-seeded, black or dark blue berry that persists throughout winter.

Ligustrin, ligustron, syringin, syringopicrin, and other unknown compounds in leaves and fruit. Primarily GI irritants. Diarrhea, abdominal pain, incoordination, paresis, weak pulse, hypothermia, convulsions, sometimes death.

Treatment symptomatic and supportive; correct dehydration.

Lupinus spp

Lupines, Silky lupine, Sink lupine, Bluebonnet

Lupinus sericeus (Lupine)
Lupinus sericeus (Lupine), close-up

Dry to moist soils, roadsides, fields, and mountains; throughout, but poisoning mostly western USA

Sheep, cattle, goats, horses, pigs

Perennials. Leaves simple or palmately divided. Flowers blue, white, red, or yellow in terminal raceme.

Quinolizidine alkaloids (20 known) concentrated in seeds (fresh and dry); some piperidine alkaloids. Acute course. Inappetence, dyspnea, struggle, convulsions, death from respiratory paralysis. Lupinosis (hepatotoxicosis) not a reported problem in the USA. Some species teratogenic in cattle (crooked calf disease, weak and deformed calves, stillbirths).

Nandina domestica

Nandina, Heavenly bamboo, Chinese sacred bamboo

Nandina domestica (Nandina, Heavenly bamboo, Chinese sacred bamboo)

Common ornamental in southern USA

All grazing animals, especially ruminants

Upright, unbranched, and multistemmed, evergreen shrub, 3–7 ft tall. Alternate, bi- to tripinnately compound leaves; leaflets subsessile, elliptic-lanceolate, half as wide as long, entire, leathery, metallic bluish-green becoming purple in fall. Small, white flowers; 2-seeded, bright red berries in large panicles persist throughout fall and winter.

Cyanogenic glycosides in foliage and fruits, hydrolyzed in GI tract to free cyanide, thereby affecting cellular respiration. See Cyanide Poisoning Cyanide Poisoning . Prognosis good if animal survives for 1 hr after signs begin.

Acute outcome precludes effective treatment for most; IV sodium nitrite/sodium thiosulfate treatment of choice. Picrate test indicates toxic potential of the plant. See Cyanide Poisoning Cyanide Poisoning .

Nerium oleander

Oleander, Laurel rosa, Laurel blanco

Nerium oleander (Oleander)
Nerium oleander (Oleander), close-up

Common ornamental in southern regions


Evergreen shrub or tree. Leaves whorled and prominently, finely, pinnately veined beneath. Flowers showy, white to deep pink.

Digitoxin-type glycosides (oleandroside, nerioside, and others) in all parts, fresh or dry. Acute course. Severe gastroenteritis, vomiting, diarrhea, increased pulse rate, weakness, death.

No specific treatment. Atropine in conjunction with propranolol reported helpful.

Photinia fraseri, P serrulata, P glabra

Fraser’s photinia, Chinese photinia, Red leaf photinia, Red tip photinia

Photinia spp (Red tip photinia)
Photinia spp (Red tip photinia), young plant
Photinia spp (Red tip photinia), flower

Common ornamental (hedge or screen) in southern USA

All grazing animals, mostly ruminants

Evergreen shrubs, 10–15 ft tall. Alternate, oblong-ovate serrated leaves, copper-red (when young) turning dark green in 2–4 wk. Prominent, whitish flowers in spring; showy, red berries in fall.

Same as for N domestica (above).

Same as for N domestica.

Pinus ponderosa

Ponderosa pine, Western yellow pine

Pinus ponderosa (Ponderosa pine)

Coniferous forests of Rocky Mountains at moderate elevations; western USA. Dangerous all seasons, especially winter.

Cattle. Sheep and deer seem not to be affected.

Evergreen tree, 150–180 ft. Leaves in groups of 3, yellowish green, 7–11 in. long. Small soft cones, seeds mature in 2–3 yr. Bark platy, reddish orange.

Unknown toxin (diterpene esters of isocupressic acid are suspected). Chronic course. Abortions in late gestation, stillbirths or weak calves, depressed, edema of vulva and udder, retained placenta.

Pine-needle ingestion during last half of gestation—may abort after single exposure. Supportive care, remove retained placenta, treat metritis, provide good nutrition. Keep pregnant cows away from source.

Prunus caroliniana

Laurel cherry, Cherry laurel, Mock orange

Woods, fence rows, and often escaped from cultivation; southern regions. Dangerous all seasons, especially winter and spring.

All grazing animals

Leaves evergreen, shiny, leathery. Broken twigs with strong cherry bark odor. Fruit black.

Hydrocyanic acid (wilted leaves, bark, and twigs). Peracute course. Difficult breathing, bloat, staggering, convulsions, followed by prostration and death. Mucous membranes and blood bright red.

Prunus spp

Chokecherries, Wild cherries, Peaches

Prunus virginiana (Choke cherry)
Prunus virginiana (Choke cherry), close-up

Waste areas, fence rows, woods, orchards, prairies, dry slopes

All grazing animals, mostly cattle and sheep

Large shrubs or trees. Flowers white or pink. Cherries or peaches. Crushed twigs with strong odor.

Glycoside-yielding cyanide (rumen hydrolysis). Excitement leading to depression, dyspnea, incoordination, convulsions, prostration. Death may occur in 15 min from asphyxiation.

Mucous membranes, bright pink color; blood, bright red color. See Cyanide Poisoning Cyanide Poisoning .

Psilostrophe spp


Open range lands and pastures; southwestern USA

Sheep primarily; cattle and goats less susceptible and less likely to eat the plant.

Perennial composite. Erect, woolly stems branching from base. Leaves simple, alternate, petioled. Many small heads of yellow flowers.

Sesquiterpene lactone. Depression, incoordination, anorexia, weakness, trembling, rapid irregular pulse and respiration, coughing, vomiting, aspiration pneumonia, death.

Antimicrobial actions of sesquiterpene lactone in rumen affect metabolism. Supplement diet with sodium sulfate and high protein.

Pteridium aquilinum

Bracken fern, Bracken, Brake fern

Pteridium aquilinum (Bracken fern)

Dry poor soil, open woods, sandy ridges, throughout North America

All grazing animals

Leaves firm, leathery, 3-pinnate.

Ricinus communis

Castor bean

Ricinus communis (Castor bean)

Cultivated in southern regions


Large, palmately lobed leaves. Seeds resembling engorged ticks, usually 3 in somewhat spiny pod.

Phytotoxin—ricin in all parts (seeds especially toxic). Acute to chronic course (death or recovery). Violent purgation, straining with bloody diarrhea, weakness, salivation, trembling, incoordination.

Diagnosis based on presence of seeds, RBC agglutination, precipitin test. Specific antiserum, ideal antidote; sedatives, arecoline hydrobromide, followed by saline cathartics suggested.

Senecio spp

Groundsel, Senecio

Senecio jacobaea (Tansy ragwort).
Senecio ridellii (Riddell's groundsel)
Senecio longilobus (Threadleaf groundsel)

Grassland areas; mostly western USA

Cattle, horses, sheep to a limited extent in USA

Perennial or annual herbs. Heads of yellow flowers with whorl of bracts below.

Pyrrolizidine alkaloids, volatile oils, and nitrogen oxides (fresh or dry). Acute poisoning not common. Dullness, aimless walking, increased pulse, rapid respiration, weakness, colic, delayed death (days to months). In cattle, prolapsed rectum from persistent straining. In horses, nervous signs evident in later stages.

Effects are cumulative. Liver biopsy diagnostic in early stages. Liver function test of value for subclinical condition in cattle. No general treatment. See also Pyrrolizidine Alkaloidosis Pyrrolizidine Alkaloidosis .

Sorghum halepense

Johnson grass

Sorghum halepense (Johnson grass)

Weed of open fields and waste places; southern and scattered north to New York and Iowa

All grazing animals

Coarse grass with large rhizomes and white midvein on leaf. Topped by large, open panicle.

Same as for S vulgare (below).

Same as for S vulgare.

Sorghum vulgare

Sorghum, Sudan grass, Kafir, Durra, Milo, Broomcorn, Schrock, etc

Sorghum vulgare (Sorghum, Sudan grass, Kafir, Durra, Milo, Broom-corn, Schrock, etc)

Forage crops and escapes; throughout North America


Coarse grasses with terminal flower cluster. Some to 8 ft tall.

Hydrocyanic acid (drought, trampling, frost, second growth) and nitrate (heavy in vegetative parts). Acute 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). See Cyanide Poisoning Cyanide Poisoning , and see Nitrate and Nitrite Poisoning Nitrate and Nitrite Poisoning .

Taxus spp


Taxus spp (Yew)

Most of North America; Japanese and English yew common ornamentals

All except deer

Evergreen perennial tree or shrub. Bark reddish brown then flaking in scales. Leaves linear, 0.5–1 in. (1.5–2.5 cm) long, 2-ranked on twig, upper surface dark green, lower yellow-green, midribs prominent. Flowers unisexual, inconspicuous. Fruit single stony seed. Bright scarlet color.

Toxic alkaloids in bark, leaves, seeds. Gaseous distress, diarrhea, vomiting, tremors, dyspnea, dilated pupils, respiratory difficulty, weakness, fatigue, collapse, coma, convulsions, bradycardia, circulatory failure, death. Death may be rapid.

Poisoning usually results when branches and trimmings fed to livestock.

Triglochin spp


Triglochin maritima (Arrow grass)

Salt marshes, wet alkaline soils, lake shores; dangerous all seasons, especially dry season; northern half of North America

Sheep, cattle

Grasslike, except leaves are thick. Heads of fruits globular on erect raceme. Flowers inconspicuous.

Hydrocyanic acid in leaves. Salivation, dyspnea, excitement followed by depression, incoordination, prostration, convulsions followed by death from anoxia.

Often, animals found dead. See Cyanide Poisoning Cyanide Poisoning .