There are many types of plants and shrubs that are harmful to horses, and in some cases, consuming them can be fatal.

It is therefore essential that you exercise good paddock maintenance and make sure you remove trees or plants that could pose a danger to your horse.

If necessary, put out extra hay or haylage to supplement your horse’s grazing, so that he’s not hungry and could be tempted to eat anything potentially harmful.

Below is a list of typical British plants that are harmful to horses.  In all cases, if you suspect your horse has eaten a poisonous plant, seek immediate veterinary attention.

Bracken/fern

Ferns are not particularly palatable to horses as they taste bitter.  However, during the autumn months when the ferns have died back and become bracken, there’s a danger that hungry horses will ingest them.

A large quantity of fern/bracken would have to be eaten to cause the following obvious symptoms:

• depression
• muscle tremors
• ataxia (loss of coordination)
• slow heartbeat

Buttercup

Buttercups contain irritant juices that can cause inflammation to the stomach.  The plant’s sap can also cause irritation and blistering of the horse’s skin.

Symptoms of buttercup poisoning include:

• mouth blisters
• drooling
• loss of appetite
• colic
• bloody urine
• diarrhoea
• colic
• twitching of the eyelids
• loud breathing
• weak pulse

A vet should be called immediately to reduce the damage caused by eating buttercups. There is no known antidote for the poison, and so pasture management is the key to prevention.

Cowbane/water hemlock

Cowbane or water hemlock is a member of the parsley family, but unlike common cow parsley, it’s extremely toxic to horses, all other wildlife, and humans.

Eating just a few hundred grams of the plant can be fatal.  Cowbane is found in damp marshy areas or growing along the water ditches that often border grazing.

Symptoms of cowbane poisoning include:

• salivation
• dilated pupils
• spasms and convulsions
• abdominal pain

The plant’s poisons can be fatal in just a few hours, with immediate attention required from your vet.

Laburnum

Laburnum is an ornamental tree with hanging yellow flowers and black seed pods.

All parts of the tree are toxic to horses and other grazing animals, but thanks to its bitter taste, the tree is usually given a wide berth.

Laburnum poisoning symptoms include:

• abdominal pain
• convulsions
• muscle spasms
• lack of coordination
• in severe cases, coma and death

If you think that your horse has eaten laburnum, immediate attention by a veterinary surgeon is required.

Oak

Oak leaves and acorns contain a small amount of tannic acid, which is harmless to horses in very small quantities.

However, the leaves can be addictive, and once horses get a taste for them, they will actively search them out.

Regular consumption of oak can cause gastroenteritis and kidney damage.

Symptoms include:

• lack of appetite
• staring coat
• constipation followed by diarrhoea which may be blood-stained
• abdominal pain
• depression
• blood in urine

There is no antidote to oak poisoning; however, the horse can be treated with antibiotics or other medicines to control the pain or diarrhoea.

Ragwort

Ragwort is a very common weed that grows and spreads very quickly.  All landowners have a duty to remove and carefully dispose of ragwort.

Generally, this plant has a bitter taste and horses will not eat it.  However, when dried, the weed loses its bitterness and is often consumed accidentally when it’s hidden in hay or haylage.

Ragwort poison builds up in a horse’s system where it can cause irreversible liver damage, whether eaten in small quantities regularly over time or in a large amount in one sitting.

Symptoms of ragwort poisoning include:

• weight loss
• poor and staring coat
• staggering gait
• impaired vision
• inability to swallow
• paralysis

Ragwort poisoning is irreversible, and so the emphasis is on prevention and good pasture management.

Yew

The whole of the yew tree is extremely toxic.

Only a few hundred grams of the fresh plant are capable of killing an adult horse within a few minutes.

Yew trees are often found in hedging, especially in fields bordering old estates where the plant was traditionally used.

Symptoms of yew tree poisoning include:

• trembling
• muscle weakness
• irregular heartbeat
• slow heartbeat
• difficulty breathing
• nervousness
• convulsions

Yew tree poisoning can be treated if discovered quickly and treated immediately.  Always call your vet if you think your horse has eaten yew foliage or berries.

Sycamore

Atypical myopathy is a disease of the autumn months when the box elder or sycamore tree releases its winged seeds.

Horses ingest the seeds whilst grazing beneath the trees and succumb to poisoning.

Symptoms of atypical myopathy

• muscular stiffness
• reluctance to walk
• muscle tremors
• sweating
• depression and/or the horse looks as if it is sedated
• high heart rate
• dark urine
• the horse appears weak and may have difficulty standing
• breathing difficulties
• the horse may still want to eat

Immediate veterinary attention is required, but the condition is treatable.

In conclusion

Unfortunately, there are many cases of equine poisoning every year.  You can help to keep your horse safe by checking your turnout regularly to make sure there are no poisonous plants or trees growing on the land, or overhanging it.

In general, horses won’t knowingly eat toxic plants.  They are usually consumed accidentally in hay or haylage, or if there is nothing else to eat in the field.

Always ensure that your feed supplier is reputable, and shake out hay before feeding it to horses to check for dried plants like ragwort.

Related Reads: 

• About Your Horse’s Digestive System
• How to Feed for the Dressage Arena
• How to Identify and Manage Laminitis
• How to Manage Mud Fever in Horses