List of plants poisonous to equines

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Paterson's Curse has been responsible for the deaths of many horses.

Many plants are poisonous to equines; the species vary depending on location, climate, and grazing conditions. In many cases, entire genera are poisonous to equines and include many species spread over several continents. Plants can cause reactions ranging from laminitis (found in horses bedded on shavings from black walnut trees), anemia, kidney disease and kidney failure (from eating the wilted leaves of red maples), to cyanide poisoning (from the ingestion of plant matter from members of the Prunus genus) and other symptoms. Members of the Prunus genus have also been theorized to be at fault for mare reproductive loss syndrome.[1] Some plants, including yews, are deadly and extremely fast-acting.[2] Several plants, including nightshade, become more toxic as they wilt and die, posing a danger to horses eating dried hay or plant matter blown into their pastures.[3]

The risk of animals becoming ill during the fall is increased, as many plants slow their growth in preparation for winter, and equines begin to browse on the remaining plants. Many toxic plants are unpalatable, so animals avoid them where possible. However, this is not always the case; locoweeds, for example, are addictive and once a horse has eaten them, it will continue to eat them whenever possible, and can never be exposed to them again. When a toxic plant is ingested, it can be difficult to diagnose, because exposure over time can cause symptoms to occur after the animal is no longer exposed to the plant. Toxins are often metabolized before the symptoms become obvious, making it hard or impossible to test for them.[4] Hungry or thirsty horses are more likely to eat poisonous plants, as are those pastured on overgrazed lands.[5] Animals with mineral deficiencies due to poor diets will sometimes seek out poisonous plants.[6] Poisonous plants are more of a danger to livestock after wildfires, as they often regrow more quickly.[7]

Poisonous plants[edit]

Crofton weed (Ageratina adenophora) (flowers and leaves)
The deadly Nerium oleander
Scientific name Common name Notes References
Abrus precatorius Crab's eye Also known as precatory bean, rosary pea, or jequirity bean [8]
Acer rubrum Red maple, also known as swamp or soft maple [4]
Adonis microcarpa Pheasant's eye [9]
Aesculus hippocastanum Horse chestnut Also known as buckeye [3]
Ageratina Snakeroots Known poisonous species include Ageratina adenophora (Crofton weed, causes Tallebudgera horse disease) and Ageratina altissima (white snakeroot) [3][10]
Aleurites Tung oil tree [8]
Amsinckia intermedia Fiddleneck [11]
Apocynum cannabinum Hemp dogbane Also known as Indian hemp, choctaw root, rheumatism weed, and snake’s milk [5]
Arctotheca calendula Cape weed [9]
Armoracia lapathifolia Horseradish [8]
Artemisia Known poisonous species include Artemisia tridentata (big sagebrush) and Artemisia filifolia (sand sagebrush) [8]
Asclepias syriaca Common milkweed [4]
Astragalus Locoweed, crazy weed, or milk vetch Addictive [4][12]
Atropa belladonna Deadly nightshade or belladonna [13]
Baptisia False indigo [8]
Berteroa incana Hoary alyssum [14]
Brassica Mustards [5]
Buxus sempervirens Boxwood [3]
Celastrus scandens Climbing bittersweet [8]
Centaurea Thistles Known poisonous species include Centaurea solstitialis (yellow star thistle or St. Barnaby's thistle) and Centaurea repens (Russian knapweed) [3][9]
Cestrum parqui Green cestrum [13]
Chrysothamnus nauseosus Rubber rabbitbrush [8]
Cicuta Water hemlock, cowsbane [3]
Claviceps paspali Paspalum ergot [9]
Conium maculatum Hemlock or poison hemlock [9]
Corydalis Fitweed, fumitory [8]
Craspedia chrysantha Round billy button or woollyhead [9]
Crotalaria Rattlepods [15]
Cucumis myriocarpus Paddy melon [9]
Cuscuta Dodder [8]
Cynoglossum officinale Houndstongue [6]
Datura Jimsonweed, thorn-apple [4][9]
Delphinium Larkspur [3]
Dendrocnide moroides Stinging tree or Gympie stinger [13]
Descurainia pinnata Tansy mustard [8]
Digitalis Foxgloves [3]
Dryopteris filix-mas Male fern [8]
Duboisia Corkwoods [13]
Echium plantagineum Paterson's curse Also known as Salvation Jane, blue weed and Lady Campbell weed [9][16]
Equisetum Horsetails, mare's tails, scouring rush [12]
Erythrophleum chlorostachys Cooktown ironwood [15]
Euphorbia Spurges [8]
Festuca arundinacea Tall fescue [3]
Franseria discolor White ragweed [8]
Glechoma hederacea Ground ivy Also known as creeping charlie [3]
Grindelia Gumweeds [8]
Haplopappus heterophyllus Rayless goldenweed Also known as jimmyweed or burrow weed [8]
Heliotropium Heliotropes Known poisonous species include Heliotropium amplexicaule (blue heliotrope), H. europaeum (common heliotrope), and H. supinum (creeping heliotrope) [9][13][17]
Homeria Cape tulips [18]
Hypericum perforatum St. John's wort Also known as Klamath weed [3]
Hypochaeris radicata Flatweed or catsear Has been implicated in causing Australian stringhalt, possibly due to a toxic mold that grows on it, especially poisonous to draft horses [9][19]
Juglans nigra Black walnut Bedding horses in shavings or sawdust can cause laminitis [3]
Juniperus virginiana Juniper [8]
Kalmia latifolia Mountain laurel or spoonwood Also known as spoonwood or calico bush [13]
Kochia scoparia Burning bush Also known as summer cypress or Mexican firewood [8]
Lantana camara Yellow sage [20]
Ligustrum Privets [13]
Lolium perenne Perennial ryegrass [9]
Lupinus Lupins [3]
Malva parviflora Mallow [9]
Marsilea drummondii Nardoo Contains an enzyme which destroys vitamin B1, leading to brain damage in sheep and horses [9]
Melilotus Sweetclover Includes Melilotus alba (white sweetclover) and M. officinalis (yellow sweetclover), can be grazed as a forage crop, but mold or spoilage converts coumarins to toxic dicumarol, thus moldy hay or silage is dangerous [5]
Nerium oleander Oleander Also known as rose laurel, adelfa, or rosenlorbeer [3][12]
Nicotiana Tobacco [13]
Onoclea sensibilis Sensitive fern or meadow fern [8]
Oxytropis Locoweed or crazy weed Addictive [4][12]
Persea americana Avocado [21]
Physalis Japanese lanterns, groundcherries [4][5]
Phytolacca americana Pokeweed [4]
Prunus Cherries, apricots, peaches, and plums [4]
Pteridium esculentum/P. aquilinum Bracken fern [4][9][12]
Quercus Oaks [1]
Ranunculus Buttercups [9]
Raphanus Radishes [5]
Rhododendron Azaleas, laurels, and rose bays [12]
Ricinus communis Castor oil plant Also known as the castor bean or palma Christi, fatal even in small amounts [3][12]
Robinia pseudoacacia Black locust Also known as false acacia [3][4]
Romulea Known poisonous species include Romulea longifolia (Guildford grass) and R. rosea (onion grass or onion weed) [9][18]
Rudbeckia laciniata Goldenglow, coneflower, or thimbleweed [8]
Senecio Ragworts, groundsel, or stinking willy [4][9]
Silybum marianum Variegated thistle Poisons cattle, sheep, and rarely horses [9]
Solanum Potatoes, tomatoes, nightshades, horse nettle, ground cherry, or Jerusalem cherry [3][4]
Solidago Goldenrod [8]
Sorghum Sudan grass, Johnson grass Cyanide produced after stress [4][9][12]
Stachys arvensis Field woundwort or stagger weed [22]
Stipa viridula Sleepy grass [8]
Swainsona Darling peas [9]
Taraxacum officinale Dandelion When infected with a toxic mold that grows on it, the plant has been linked to outbreaks of Australian stringhalt. [19]
Taxus Yews [12]
Trifolium pratense Red clover [3]
Vinca major Blue periwinkle or large periwinkle [9]
Wislizenia refracta Jackass clover [8]
Xanthium strumarium Cocklebur [5]
Zephyranthes atamasca Atamasco lily or rain lily [8]


  1. ^ a b Cable, Christina (2002-04-01). "Which Trees are Toxic?". The Horse. Retrieved 2010-12-07. (registration required (help)). 
  2. ^ "Poisonous Plants: Yew". Horse & Hound. 2001-06-25. Retrieved 2010-12-12. 
  3. ^ a b c d e f g h i j k l m n o p q r King, Marcia (2001-05-01). "Poisonous Plants". The Horse. Retrieved 2010-12-07. (registration required (help)). 
  4. ^ a b c d e f g h i j k l m n DeLong, Jodi (2008-10-10). "Poisonous Plant Risk Increases as Pasture Grass Goes Dormant". The Horse. Retrieved 2010-12-06. (registration required (help)). 
  5. ^ a b c d e f g "Horse Nutrition". Ohio State University. Retrieved 2010-12-08. 
  6. ^ a b Israelsen, Clark E.; McKendrick, Scott S.; Bagley, Clell V. (2006-10-01). "Poisonous Plants and Equines" (PDF). Utah State University. Retrieved 2010-12-08. 
  7. ^ Knight, James E. (2002). "After Wildfire" (PDF). Montana State University. Retrieved 2010-12-15. 
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w DiTomaso, Joseph M. (1994). "List of Plants Reported to be Poisonous to Animals in the United States" (PDF). 36:49-52. Veterinary and Human Toxicology.  Also,
  9. ^ a b c d e f g h i j k l m n o p q r s t u v McBarron, E.J. (1983). Poisonous Plants. Melbourne: Inkata Press. ISBN 0-09-096029-7. 
  10. ^ Jordan, Sonia (2010-10-26). "Crofton weed". The State of Queensland. Retrieved 2010-12-06. 
  11. ^ "Toxic Plants in Your Hay and Pasture". University of California – Davis. Retrieved 2010-12-07. 
  12. ^ a b c d e f g h i Lamm, Willis (1997). "Poisonous Plants". TrailBlazer Magazine. Retrieved 2010-12-06. 
  13. ^ a b c d e f g h Offord, Mellisa. "Plants Poisonous to Horses: An Australian Field Guide" (PDF). Rural Industries Research and Development Corporation, Australian Government. Retrieved 2010-12-08. 
  14. ^ Michigan State University Extension (2008-07-17). "Horse Owners Cautioned about Hardy Toxic Plant". The Horse. Retrieved 2010-12-07. (registration required (help)). 
  15. ^ a b McKenzie, Ross. "Australian Native Poisonous Plants". Australian Native Plants Society. Archived from the original on 2011-04-10. Retrieved 2010-12-06. 
  16. ^ "Toxic Plants". Tamworth Regional Council. Retrieved 2010-12-06. 
  17. ^ "Common heliotrope" (PDF). New South Wales Department of Agriculture. 2004–05. Retrieved 2010-12-08.  Check date values in: |date= (help)
  18. ^ a b "Common pasture weeds that may poison horses". Government of South Australia. 2008-11-20. Retrieved 2010-12-06. 
  19. ^ a b Kohnke, John. "Australian stringhalt" (PDF). South East Victoria Equine Network. Retrieved 2010-12-06. 
  20. ^ "Lantana (Lantana camara L.)". University of Illinois at Urbana-Champaign. Retrieved 2010-12-12. 
  21. ^ "Avocado". University of Pennsylvania. 2002. Retrieved 2010-12-07. 
  22. ^ "Important Poisonous Vascular Plants of Australia". Merck & Co., Inc. 2008. Retrieved 2010-12-08. 

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