Plants Toxic to Horses

will generally avoid eating buttercups because of their acrid taste and tendency to blister the mouth. After a hard frost or if dried in hay buttercups are no longer toxic Buttercups may cause1
irritation of the mouth area such as blisters drooling
Bracken Fern

Bracken fern is very common as it can be found growing along roadsides in fields in light bushy areas and even gardens. In the spring fiddleheads unfurl into triangular fronds. Bracken fern dried and baled into hay is still toxic. If a horse eats a large quantity of this fern the toxins can cause a vitamin B1 deficiency Symptoms of bracken fern poisoning may include1
weight loss
weakness
gait abnormalities
abnormal heart rate andor rhythm
inability to rise
death
Horse Tails
Soils comprised largely of sand and gravel drain quickly making them perfect for this variety of horsetail. Other varieties grow in more marshy areas. The plant can be toxic whether dried and baled into hay or consumed as the fresh plant. The toxin in this plant inactivates thiamin vitamin B1 in the horses gastrointestinal tract.
Symptoms of horsetail poisoning include2
weakness especially in the hind legs
depression
constipation
Lambs Quarters or Pigweed
In some areas this plant is called pigweed or goosefoot. The leaves can be broad with varying shapes and are covered in a whitish coating. The stems are smooth and can be green or have a reddish tinge. The flower looks rather like a small pale green cauliflower cluster. It is a very common weed in gardens.
A horse would have to eat a large number of lambs quarters for the toxin to take effect. Unless there is no other feed available it is unlikely a horse will eat this plant.
If a horse consumes a large number of lambs quarters symptoms may include3
weakness
respiratory distress
coma
kidney failure
Lily of the Valley
Its a lovely springblooming perennial bulb but its toxic to horses. Does this grow in your flower garden?
This common garden plant is toxic to humans and pets including horses. Lily of the valley is unlikely to be growing in a pasture as it is typically planted in house gardens because of its attractive flowers and pretty red berries. It could be accidentally ingested if someone were to throw garden clippings close to a fence line where curious horses might be able to reach. Garden and lawn clippings should be disposed of in an area that is out of the reach of horses.
The plants toxins affect the heart. Ingestion may result in4
irregular heart rhythm
low