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Home | Plant treatments that are safe for horses

Resources for Info on Plants and Flowers that are Toxic to Horses

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Generally, in the US, each state has some info available about poisonous plants in their state/region via the state universities that are oriented to vet training.  Certain private universities will offer information too.  

Canada has a Ministry office that has a list and resources for particular provinces.

 The following is a limited reference list for resources.  Feel free to send a link if you know of a particularly useful one.  Canada links provided too.* 



University of California at Davis General information on US poisonous plants, listed by type of injury (mechanical, digestive, etc). Pdf download.   General list of poisonous plants that includes Toxicity class and what to do if exposed to such.  Includes California emergency phone contacts.


CANADA Ontario, Canada's Ministry of Agriculture and Food; list of plants, pictures, symptoms of poisoning, emergency phone contacts.

Noteable common plants:  buttercups, yews, oleander, field horsetail, some ferns. 

Canadian government Poisonous Plant Information System



Colorado State University

Large general database; enter “horse” in the search box—comes up with 82 common and botanical names of plants and flowers with pictures, link to further information.  The info includes how to diagnose, treatment and symptoms of poisoning, and a map showing the primary areas that are affected.  Includes more scientifically technical information.



Kathryn Watts has a website on primarily grass founder.  Offers research and consulting services nationwide.



Just provides a list, no further information

List includes: African violets, dieffenbach, philodendron, impatiens, yew evergreens, angels trumpet




Purdue University

Direct listing of common names of plants and link to info for horses, all animals, pets.  Info includes pictures, causes, symptoms, immediate action to take, contact phone numbers.

Noteable common plants: oats with lots of nitrate, st.johnswort, johnsongrass, fescue, lupine.




Cornell University





North Dakota University



Ohio State University online--covers mostly Ohio, however includes extensive info on plants that may be found many places, including poison and symptoms.





The Noble Foundation in Ardmore, Oklahoma offers an excellent site for any and all information on horse pastures in the Southwest region in particular—from start to finish under the heading “Horse Forage and Forage Management”.

The above link is direct to the poisonous plant list.  Left hand side for other links within the directory.  The Plant Image directory has very specific and complete photos of many plants, flower, grasses and shrubs and trees useful in identification, as well as with information.




Oregon State University

Includes color pictures and direct link to info.

Noteable plants and flowers include: larkspur, red maple



Texas A&M

College Station, Tx. List of house and outside plants by terrain that are poisonous.  Handy one page list.   Concise article on plant poisoning in horses and plants that cause them. Toxic plant management booklet for the Texas-Pecos region—pdf download.



US Department of Agriculture list of links to information on toxic plants and flowers.  This includes plants that are toxic to humans.

Poisonous and Medicinal Plants Links




University of Wisconsin

 Excellent article that includes a list of poisonous pasture weeds and discussion of recent research findings; with references cited.  Early 90's publishing date.

 A general guide to Toxic insects, plants and wildlife in Wisconsin.  Pdf download.



Some Ornamental Plants, Shrubs and Trees Potentially Poisonous for Horses and  Common Plants

Lots of free information on laminitis (founder)






Horse Poisoning from Oregon State University

. Poisonings are most likely to occur with very young animals or animals newly brought into the area.
2. Generally, livestock do not graze toxic plants in a pasture as long as there is abundant, palatable feed. (Tall larkspur and lambsquarters are exceptions.)
3. Examine pastures in August. Weedy species left untouched are either toxic, unpalatable or thorny.
4. Most poisonings occur in hay, so check hay closely for weeds. Starthistle can be a hay contaminant from southern or eastern
5. Foxtail Barley and Medusahead cause mechanical injuries.
6. Lambsquarters and Amaranth are nitrogen accumulators.
7. The corn family foliage, when frosted or drought stressed, is toxic to horses.
8. Blister beetles are very toxic to horses and are sometimes found in hay. There are many kinds of blister beetles that feed on hay and pasture crops.
9. Camelids have other toxin problems.There are many poisonous plants that may be toxic to livestock and horses that are not referenced on this list.

Do not assume a plant is not toxic just because it is not listed here.This material is provided as information only and is not to be used for the home treatment of animals.

Please contact your veterinarian or poison control if poisoning is suspected.

For further information, the Cornell University website contains many links to information on poisonous plants,

Authors: Ross Penhallegon, Pat Patterson, Larry Campbell, Pete Schreder
County Extension
Revised March 2002

last updated July 16, 2003


PLANT TOXICITY in HORSES FROM the Canadian Ministry

Horses will usually avoid eating poisonous plants (they don't taste very good) as long as there is an abundant supply of good quality hay or pasture available. However, faced with no pasture or hay, a horse might decide to sample one of the poisonous weeds still left standing in the field.

The best medicine for dealing with poisonous plants is ... PREVENTION.

  • Ensure that horses on pasture have adequate hay and/or pasture so that they won't have to resort to eating poisonous weeds.
  • Avoid overgrazing, if no supplemental hay is provided.
  • Learn to recognize poisonous weeds and control them by pulling or by use of commercially registered herbicides.
  • Examine your hay for unwanted plants.


Did you know?


Carbohydrate levels in grass can increase the chances of your horses foundering.



Black walnuts can cause founder (stablemade link)


A single ounce of oleander leaves can kill a 1000 pound horse—it has an effect similar to digitalis in human on the heart.  (Several databases including Purdue).


Needles from yews whether dead or alive can cause immediate sudden death.  Yews are often used in containers, so avoid for decoration of rings, etc. (several databases, including Purdue)


Johnson grass contains cyanide in leaves and stems. (Purdue)

Toxic levels of nitrates can accumulate in Johnsongrass following heavy fertilization or drought and result in toxicosis which be confused with cyanide poisoning

 (Ohio State info)


Two safe plants are crepe myrtle and red photip.  (Texas A&M)


Many species of cherry and peach trees are poisonous--once eaten, they produce cyanide poisoning in the digestive tract.  Does seem to affect ruminant animals more than horses, however, it does result in death within an hour.  Includes eating of wilted leaves.  (Ohio State)



*L.Robinson is not responsible for any of the accuracy of any of the information provided. 

copyright 2004--L.Robinson,agent
The above information is provided solely for  educational purposes