Spring Plants that are Poisonous to Horses, Dogs and Barn Cats

Oleander colic diarrhea possibly bloody sweating incoordination shallowdifficult breathing muscle tremors recumbence and possibly death from cardiac failure. The plant is pretty and poisonous. It can severely affect cats dogs and even horses. All parts contain a highly toxic cardiac glycoside that can cause a number of problems.
Ivy
California Branching Glacier Needlepoint Sweetheart English Ivy Vomiting abdominal pain hypersalivation diarrhea. Ivy foliage is more toxic than its berries.
Lilies kidney failure. They are highly toxic to cats even when very small portions are ingested. Many types of lily Tiger Asian Japanese Show Easter Stargazer Casa Blanca can cause kidney failure in cats. Curiously lilies are not toxic to dogs.
Sago Palm a very popular landscaping plant. They are apparently very tasty to animals and unfortunately highly toxicall parts are

 poisonous but especially the seeds. Symptoms vomiting melena icterus increased thirst hemorrhagic gastroenteritis bruising coagulopathy liver damage liver failure death.
Tomato plant hypersalivation inappetence severe gastrointestinal upset diarrhea drowsiness central nerves system depression confusion behavioral change weakness dilated pupils slow heart rate. Although it wont prove lethal for your pet they can provide a good dose of discomfort.

TulipNarcissus intense gastrointestinal irritation drooling loss of appetite depression of the central nervous system convulsions and cardiac abnormalities. Its the bulb of the tulip and narcissus plants that have the highest concentration of toxins. This means if you have a dog that digs be cautious.
LilyoftheValley Causes excessive salivation watery eyes sweating abdominal pain weakness convulsions and death. This plant is largely an ornamental plant but may grow wild near old home sites. The plant is highly toxic to all animals.
Yew central nervous system effects such as trembling incoordination and difficulty breathing. It can also cause significant gastrointestinal irritation and cardiac failure which can result in death. The bark and leaves of this very popular evergreen provided the basis for the cancertreatment drug paclitaxelbut general ingestion of any part of the tree except the flesh of the berry can be very dangerous to animals. Horses have an especially low tolerance to yew.
Conclusion
When landscaping the stable area you may be better off to just plant grass and
plant the ornamentals at your home. But then you have to watch the pets and children.