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Plants Reported to be Toxic When Ingested by Horses

The following table lists common plants known to be toxic when ingested by horses. While this is not a complete list, it contains many plants commonly found in pastures and landscapes in Georgia.  Horses generally will not consume the majority of these plants unless deprived of their normal forages.

Plant Name(s)Botanical Name/FamilyToxic Plant PartsSymptoms
American PersimmonDiospyros virginiana, Ebenaceae (Ebony family)fruit skin, pulp, seedsulcers and even rupture of the stomach; severe colic; intestinal obstruction
Angel’s Trumpet**Brugmansia suaveolens (Datura suaveolens), Solanaceae (Nightshade family)seedsanorexia, weight loss, thirst, tachycardia, dilated pupils, diarrhea, excessive urination, and death
Avocado  Persea americana, Lauraceae (Laurel family)  leaves, bark, seeds, and skin of the fruitedematous swelling of the lips, mouth, eyelids, head, and neck, which can cause upper respiratory distress; colic
Black LocustRobinia pseudoacacia, Fabaceae (Legume family)bark, seedslectins poisoning; severe gastrointestinal irritation; vomiting and diarrhea; dilated pupils and cardiac arrhythmias
Black NightshadeSolanum nigrum. Solanaceae (Nightshade family)all partstaxicardia, decreased salivation and intestinal motility, dilated pupils, and tachycardia; colic, constipation, or hemorrhagic diarrhea
Black WalnutJuglans nigra, Juglandaceae  (Walnut family)unknown- roots, bark, nuts, and pollen of the walnut tree, is possibly involvedhorses become poisoned if they are exposed to the wood shavings of black walnuts that are used for bedding. laminitis, edema of the lower legs, colic
Bleeding Heart, Dutchman’s BreechesDicentra spp., Fumariaceae      (Fumatory family)all partsprojectile vomiting, convulsions, and lateral recumbency
Bracken Fern, Brake Fern, Eagle Fern  Pteridium aquilinum, Polypodiacae (Fern family)  fern poisoning in horses is uncommondepression, muscle tremors, uncoordinated gait, especially of the hind legs and paralysis; colic, constipation, hemoglobinuria, severe anemia, elevated temperature, and rapid heart rate
Buckeye, Horse Chestnut  Aesculus spp., Hippocastanaceae (Buckeye family)young growing sprouts, leaves, immature fruit, and seedsvomiting and gastroenteritis
Castor Bean**  Ricinus communis, Euphorbiaceae (Spurge family)all parts; seeds most toxicricin toxin poisoning; severe gastrointestinal irritation; hemorrhagic diarrhea; dilated pupils and cardiac arrhythmias; death
Choke-Cherry, Black Cherry**Prunus spp., Rosaceae  (Rose family)seeds, leaves, bark, shoots; wilted leaves and new growth most toxicfatal cyanide poisoning; rapid labored breathing, frothing at the mouth, dilated pupils, ataxia, muscle tremors, convulsions; death
Common Boxwood**Buxus sempervirens, Buxaceae (Boxwood family)all parts1.5 lb of green leaves may be lethal to an adult horse; Severe gastroenteritis, colic, and hemorrhagic diarrhea; death results from respiratory failure
Common Cockle Burr  Xanthium strumarium, Asteraceae (Sunflower family)two-leafed stage of the cockle burr and seeds; bursliver poisoning; burs cause excessive salivation and mucosa ulcers
Corn Cockle  Agrostemma githago, Caryophyllaceae (Pink family)seedsgastrointestinal irritation and diarrhea
Day-Blooming JessamineCestrum diurnum, Solanaceae (Nightshade family)all partscalcification of the elastic tissues of the arteries, tendons, and ligaments
Dogbane, Indian HempApocynum cannabinum, Apocynaceae (Dogbane family)all partsAbdominal pain, colic and diarrhea; rapid breathing, cold extremities, and a rapid, weak, and irregular pulse
Field Bindweed, Morning GloryConvolvulus arvensis, Convolvulaceae (Morning glory family)all partscolic; intestinal stasis and flatulence; slow heart rate and dilated pupils
Flatweed, Cat’s Ears  Hypochaeris radicata, Asteraceae (Sunflower family)  no specific toxin has been identified in flatweedlameness syndrome characterized by high stepping and hyperflexion of the hind legs; difficulty in stepping backward
Hoary Alyssum**  Berteroa incana, Brassicaceae (Mustard family)all parts; contaminated haystiffness, limb swelling, fever, diarrhea, laminitis, intravascular hemolysis, severe hypovolemic shock, and death; abortion or premature parturition
Jimson Weed, Thornapple, Stinkweed**Datura stramonium (D. tatula), Solanaceae (Nightshade family)seedsincreased heart and respiratory rate, muscle weakness, dilated pupils, colic, and watery diarrhea; death
Kentucky Coffee Tree
American Coffee Berry**
Gymnocladus dioica, Fabaceae (Legume family)new sprouts, leaves, and the fruitsgastrointestinal irritation, vomiting, colic, and diarrhea; hypotension, decreased heart and respiratory rates, muscle paralysis, convulsions; death
Larkspur, Poison Weed  Delphinium spp., Ranunculaceae (Buttercup family)  all partsmuscle weakness; sudden collapse; rapid exhaustion; muscle twitching, abdominal pain, regurgitation, and constipation.
Mayapple, MandrakePodophylum peltatum, Berberidaceae (Barberry family)all partscolic and diarrhea; excessive salivation
Milkweeds**Asclepias spp., Asclepiadaceae (Milkweed family)all parts; milky sap or latex1.0 kg is lethal for adult horses; death in 8 to 10 hours
Monkshood, Aconite**Aconitum spp., Ranunculaceae (Buttercup family)all partsrestless, salivate excessively, develop muscle weakness, hypotension; difficulty in breathing; death  
Mountain Laurel**Kalmia latifolia, Ericaceae (Heath family)all partsgreen frothy salivation, vomiting, colic, frequent defecation, depression, weakness, ataxia; death
Oak  Quercus spp., Fagaceae (Oak family)leaf and flower buds opening in spring; acornsexcessive thirst; frequent urination; diarrhea; intestinal stasis; teeth grinding and a hunched back
Oleander**  Nerium oleander, Apocynaceae    (Dogbane family)all parts; red flower varieties most toxicsevere gastrointestinal and cardiac signs of poisoning; death
Peas, Sweet pea  Lathyrus spp., Fabaceae            (Legume family)seedsosteolathyrism; skeletal deformities and aortic rupture
Poison Hemlock, European Hemlock
Spotted Hemlock**
Conium maculatum,. Apiaceae (Parsley family)all parts; seeds highly toxicsalivation, abdominal pain, muscle tremors, and incoordination; difficulty in breathing, dilated pupils, weak pulse, and frequent urination and defecation; death
Pokeweed, Pokeberry**Phytolacca americana, Phytolaccaceae (Pokeweed family)all partsoral irritation, excessive salivation, vomiting, colic, bloody diarrhea, depression, prostration, and death
Rattlebox**  Crotalaria spp., Fabaceae           (Legume family)all parts; seeds most toxicliver disease and photosensitization; death
Red MapleAcer rubrum, Aceraceae           (Maple family)wilted or dried leaves, especially in Fall; barkacute hemolytic anemia; weakness, increased respiratory and heart rates, cyanosis, icterus, and a red-brown coloration of the urine; abortion
Rhododendron (Azalea)**  Rhododendron spp., Ericaceae (Heath family)all parts; nectaranorexia, excessive salivation, vomiting, colic, and frequent defecation; muscle weakness, bradycardia, cardiac arrhythmia, weakness, paralysis, and coma; death
Senecio, Groundsel, tansy ragwortSenecio spp., Asteraceae     (Sunflower family)all partschronic liver disease over a period of 6 or more months.
Senna, Coffee Weed, Coffee Senna, Sickle Pod  Cassia occidentalis (Senna occidentalis), Cassia obtusifolia,      (Senna obtusifolia), Fabaceae            (Legume family)all partsafebrile and severely ataxic and may die; acute liver degeneration
Sesbania, Coffee Weed, BladderpodSesbania spp. (Daubentonia and Glottidium), Fabaceae (Legume family)all parts, seeds most toxicsevere hemorrhagic diarrhea; anorexia, abdominal pain, dehydration, and prostration
Silver Leaf Nightshade, White Horse Nettle, Tropillo**Solanum elaeagnifolium, Solanaceae (Nightshade family)all parts, particularly ripe yellow berrieshorses that have recently been treated with the antiparasitic drug ivermectin develop a neurotoxicity; drooling saliva, drooping lips and ears, and head pressing; death
Sneezeweed, Bitterweed  Helenium autumnale, Asteraceae (Sunflower family)all partssneezing and vomiting; weight loss, vomiting, and secondary inhalation pneumonia
Sudan grass, Johnson grassSorghum halepense, Poaceae (Gramineae) (Grass family)all parts; cyanide poisoning when grass is stressedposterior ataxia, urinary incontinence, cystitis, and weight loss
Tobacco**Nicotiana spp., Solanaceae      (Nightshade family)leavesrapid heart rate, salivation, vomiting, colic, and diarrhea; muscle weakness, staggering, collapse of the front legs, and a rapid, weak, and irregular heart rate; respiratory paralysis, blindness, prostration, coma, and death
Water Hemlock, Cowbane, Poison Parsnip**Cicuta maculate, Apiaceae (Parsley family)all parts, particularly the tuberous roots8 oz is lethal for adult horses; muscle tremors and violent convulsions; excessive salivation, vigorous chewing movements, teeth grinding, frequent urination, and defecation are common; death in 2 to 3 hours
White Snakeroot**  Eupatorium rugosum, Asteraceae  (Sunflower family)all parts; milk from lactating animalsinitially listless, depressed, lethargic, and disinclined to move; choking; patchy sweating; irregular heart rate; death
Yew**  Taxus species, Taxaceae  (Yew family)  leaves8 to 16 oz of yew leaves is lethal for adult horses; muscle trembling, incoordination, nervousness, difficulty in breathing, slow heart rate, vomiting, diarrhea, convulsions, and death

**Reported to be fatal when ingested in quantity.

References:

Knight, Anthony P. and Walter, Richard G.  A Guide to Plant Poisoning of Animals in North America.  Jackson, WY: The Innovative Health Science Publisher; 2001.

Plants & Weeds Toxic to Horses. North Carolina Cooperative Extension, NC: Online; 2006. <http://www.ces.ncsu.edu/copubs/ag/livestock/horse/002/>

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About Paul Pugliese.

Bachelor of Science degree in Horticulture and minor in Biology from Berry College, Rome, GA in 2001; Master’s degree in Plant Protection and Pest Management from the University of Georgia in 2003; Became a Certified Arborist in June 2009 through the International Society of Arboriculture; Has worked as an Agriculture and Natural Resources County Extension Agent for UGA Extension in Cherokee County (2006-2011) and Bartow County (2011-Present).