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 nameCommon nameNotesReferences
Abrus precatoriusCrab's eyeAlso known as precatory bean, rosary pea, or jequirity bean[8]
Acer rubrumRed maple, also known as swamp or soft maple[4]
Adonis microcarpaPheasant's eye[9]
Aesculus hippocastanumHorse chestnutAlso known as buckeye[3]
AgeratinaSnakerootsKnown poisonous species include Ageratina adenophora (Crofton weed, causes Tallebudgera horse disease) and Ageratina altissima (white snakeroot)[3][10]
AleuritesTung oil tree[8]
Amsinckia intermediaFiddleneck[11]
Apocynum cannabinumHemp dogbaneAlso known as Indian hemp, choctaw root, rheumatism weed, and snake’s milk[5]
Arctotheca calendulaCape weed[9]
Armoracia lapathifoliaHorseradish[8]
ArtemisiaKnown poisonous species include Artemisia tridentata (big sagebrush) and Artemisia filifolia (sand sagebrush)[8]
Asclepias syriacaCommon milkweed[4]
AstragalusLocoweed, crazy weed, or milk vetchAddictive[4][12]
Atropa belladonnaDeadly nightshade or belladonna[13]
BaptisiaFalse indigo[8]
Berteroa incanaHoary alyssum[14]
Buxus sempervirensBoxwood[3]
Celastrus scandensClimbing bittersweet[8]
CentaureaThistlesKnown poisonous species include Centaurea solstitialis (yellow star thistle or St. Barnaby's thistle) and Centaurea repens (Russian knapweed)[3][9]
Cestrum parquiGreen cestrum[13]
Chrysothamnus nauseosusRubber rabbitbrush[8]
CicutaWater hemlock, cowsbane[3]
Claviceps paspaliPaspalum ergot[9]
Conium maculatumHemlock or poison hemlock[9]
CorydalisFitweed, fumitory[8]
Craspedia chrysanthaRound billy button or woollyhead[9]
Cucumis myriocarpusPaddy melon[9]
Cynoglossum officinaleHoundstongue[6]
DaturaJimsonweed, thorn-apple[4][9]
Dendrocnide moroidesStinging tree or Gympie stinger[13]
Descurainia pinnataTansy mustard[8]
Dryopteris filix-masMale fern[8]
Echium plantagineumPaterson's curseAlso known as Salvation Jane, blue weed and Lady Campbell weed[9][16]
EquisetumHorsetails, mare's tails, scouring rush[12]
Erythrophleum chlorostachysCooktown ironwood[15]
Festuca arundinaceaTall fescue[3]
Franseria discolorWhite ragweed[8]
Glechoma hederaceaGround ivyAlso known as creeping charlie[3]
Haplopappus heterophyllusRayless goldenweedAlso known as jimmyweed or burrow weed[8]
HeliotropiumHeliotropesKnown poisonous species include Heliotropium amplexicaule (blue heliotrope), H. europaeum (common heliotrope), and H. supinum (creeping heliotrope)[9][13][17]
HomeriaCape tulips[18]
Hypericum perforatumSt. John's wortAlso known as Klamath weed[3]
Hypochaeris radicataFlatweed or catsearHas been implicated in causing Australian stringhalt, possibly due to a toxic mold that grows on it, especially poisonous to draft horses[9][19]
Juglans nigraBlack walnutBedding horses in shavings or sawdust can cause laminitis[3]
Juniperus virginianaJuniper[8]
Kalmia latifoliaMountain laurel or spoonwoodAlso known as spoonwood or calico bush[13]
Kochia scopariaBurning bushAlso known as summer cypress or Mexican firewood[8]
Lantana camaraYellow sage[20]
Lolium perennePerennial ryegrass[9]
Malva parvifloraMallow[9]
Marsilea drummondiiNardooContains an enzyme which destroys vitamin B1, leading to brain damage in sheep and horses[9]
MelilotusSweetcloverIncludes 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 oleanderOleanderAlso known as rose laurel, adelfa, or rosenlorbeer[3][12]
Onoclea sensibilisSensitive fern or meadow fern[8]
OxytropisLocoweed or crazy weedAddictive[4][12]
Persea americanaAvocado[21]
PhysalisJapanese lanterns, groundcherries[4][5]
Phytolacca americanaPokeweed[4]
PrunusCherries, apricots, peaches, and plums[4]
Pteridium esculentum/P. aquilinumBracken fern[4][9][12]
RhododendronAzaleas, laurels, and rose bays[12]
Ricinus communisCastor oil plantAlso known as the castor bean or palma Christi, fatal even in small amounts[3][12]
Robinia pseudoacaciaBlack locustAlso known as false acacia[3][4]
RomuleaKnown poisonous species include Romulea longifolia (Guildford grass) and R. rosea (onion grass or onion weed)[9][18]
Rudbeckia laciniataGoldenglow, coneflower, or thimbleweed[8]
SenecioRagworts, groundsel, or stinking willy[4][9]
Silybum marianumVariegated thistlePoisons cattle, sheep, and rarely horses[9]
SolanumPotatoes, tomatoes, nightshades, horse nettle, ground cherry, or Jerusalem cherry[3][4]
SorghumSudan grass, Johnson grassCyanide produced after stress[4][9][12]
Stachys arvensisField woundwort or stagger weed[22]
Stipa viridulaSleepy grass[8]
SwainsonaDarling peas[9]
Taraxacum officinaleDandelionWhen infected with a toxic mold that grows on it, the plant has been linked to outbreaks of Australian stringhalt.[19]
Trifolium pratenseRed clover[3]
Vinca majorBlue periwinkle or large periwinkle[9]
Wislizenia refractaJackass clover[8]
Xanthium strumariumCocklebur[5]
Zephyranthes atamascoAtamasco 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". 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 Plants Society. 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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