13 Deadly Plants to Horses

Find out about plants that are a danger to your horses

Your Guide To 13 Deadly Plants That Are Poisonous To Horses

Spare a moment to take note of these common horse killer plants.  Whilst the list isn’t exhaustive, it should give you a good idea about how to spot some of the common killers and what do to about them.

  • Ragwort
  • Foxglove
  • Yew
  • Oak
  • Privet
  • Deadly Nightshade
  • Cowbane/Hemlock
  • Bracken Fern
  • Buttercup
  • Horsetail
  • Charlock
  • Monkshood


If our lives weren’t considered busy enough caring for horses, riding them, training them, cherishing them.  Just think, one small plant could end that and leave you devastated.

Of course, every horse owner should ensure that the paddocks are free from droppings, grazing is rotated, and fences aren’t damaged.  But that’s not all, pastures and hedgerows are prone to weeds just like in domestic gardens and a good owner keeps a watchful eye over every acre.  In the UK there are still a number of trees and weeds that are exceedingly dangerous for horses to ingest.  Every owner should be aware of what to look for, how to remove dangerous plants and diagnose potential symptoms of ingestion.  Please read on to find out more:

RAGWORT (Senecio jacobaea)

This plant is commonly found in pastures and growing up to 3 feet high when it flowers from July to October.  Its flowers are unmistakably daisy-like and yellow.  Their seeds are often spread far and wide in the wind and can become difficult to control if left alone.

Ragwort is a slow killer because it slowly damages the liver when eaten.  In many cases, you don’t know your horse has eaten it until it is too late as the toxic effect builds up over time causing irreversible damage. Your horse can become just as ill from eating small amounts over a long period of time to eating a large quantity at once. 

A poisoned horse will lose weight despite eating normally

They can suffer photosensitisation where areas of skin become inflamed and extremely painful in sunlight, like extreme sunburn.

Eventually, most horses go blind and collapse.

The symptoms followed by death can often happen quite quickly and sometimes owners find their horse dead without warning!

A great way to deal with ragwort is to dig up the weed completely from your field. Make sure you pull it up by the roots and burn the plants, so no pollen can spread. Alternatively, you can contact DEFRA who are able to advise on other methods of control.

Be aware that ragwort is an extremely resilient plant and will nearly always grow back and spread to other pastures.  Early and decisive intervention is key to controlling this plant.

FOXGLOVE (Digitalis)

Foxgloves are very beautiful wildflowers often commonly found in many English country gardens.  Often they grow up to 1 to 1.5 metres in height and produce very distinctive bell-shaped pink flowers.  Foxglove is most poisonous when the sun is at it’s brightest because the production of toxins peaks when the plant is photosynthesizing in the midday sun.

100g of foxglove could prove fatal.  Symptoms include diarrhoea, abdominal pain, drowsiness, depression, staggering, fitting, convulsions and heart failure.

Foxglove contains a cardiac glycoside called digitoxin which is commonly used as a carefully controlled heart medication for humans and horses.

In effect, a large dose of digitoxin increases the strength of the heart contraction but slows conduction between the top and bottom part of the heart.  Therefore this leads to an irregular heartbeat and if the dose is enough, cardia arrest.  If you notice symptoms early enough, call your vet for advice as the condition can be treatable.

Foxglove has been known to be accidentally harvested with hay so always check your hay regularly. Make sure your hay producer understands the risks of accidental ingestion of foxglove to horses so they eradicate any foxglove found in their fields.

Any foxglove found in pastures where your horses graze should be removed with care and disposed of safely.  Be sure to handle foxglove with gloves and thoroughly wash your hands afterwards because the plant is deadly to humans with the same effect.

YEW (Taxus Baccata)

Yew is a small to medium-sized evergreen tree that is extremely dangerous to most livestock.  The leaves and bark as fresh or dead are lethal to a horse if eaten.  Even a small 8oz dose is enough to kill a horse in 5 minutes.

The symptoms of yew poisoning are trembling; muscle weakness; slow or irregular heartbeat and convulsions.

Like other plants, yew contains alkaloids that destroy the heart muscles.  If not diagnosed quickly this will lead to a heart attack.  Vets can use atropine to stabilise the heart and detoxify the horse system. It is recommended that no animal should be placed in a pasture near yew trees.

OAK (Quercus)

Horses love to eat oak leaves and acorns but it causes them a number of digestion problems that can kill a weak horse.

Symptoms start with a loss of appetite until the poison reaches the bowels.  Here it tends to cause constipation, diarrhoea, colic and a lot of discomforts.

PRIVET (Ligustrum)

Privet causes horses severe gastrointestinal distress as they cannot digest it.  The privet plant is commonly planted as hedges because it is reliably evergreen.

Symptoms of privet poisoning are staggering; diarrhoea; convulsions; and paralysis. A horse will die within 4 to 48 hours after eating the privet if a vet is not brought in to give treatment.

Privet, although great as hedges, should be planted out of the reach of horses. Avoid privet when out hacking if you choose to stop to graze your horse.

DEADLY NIGHTSHADE (Atropa Belladonna)

Despite the name, deadly nightshade does not usually result in a fatality but it can cause discomfort and unconsciousness.

The plant has small, usually white, star-shaped flowers and produces green berries that ripen to black or dark purple. Every part of the plant is toxic, the worst being the stems and leaves. The berries are also toxic but do decrease in toxicity once they ripen.

Poisoning by deadly nightshade usually builds up to chronic levels before the symptoms are noticed, much like ragwort.

Generally, deadly nightshade is naturally unpalatable to horses and they are more likely to graze on other grasses and plants.

Poisoning can make your horse very sick and it is recommended that if you suspect ingestion, remove the horse from the pasture and put them in a stable.  Consult veterinary advice.

COWBANE/HEMLOCK (Conium Maculatum)

The name cowbane is due to its toxicity to cattle however most people know of this plant as hemlock.

In this case, only the roots of the plant are toxic part as they contain cicutoxin.  Like ragwort, hemlock contains alkaloids that causes respiratory paralysis. There have been cases where animals have died because it was accidentally mixed into hay and forage.

It is not common for horses to eat the roots of hemlock plants, however, accidents do happen.

When eaten, symptoms include convulsions, colic and dilated pupils. It’s been suggested that if the horse survives the first few hours, they are likely to be fine in a few days.

Ideally, when found, Hemlock should be removed and burnt if found.  For best results in slowing down the spread, remove the plants in the springtime.


Admittedly bracken fern isn’t a common sight for most of us because the plants prefer well-drained moorland.  However, this fern can kill horses if eaten repeatedly over a long period of time. That being said, most horses and ponies will avoid it unless lack of food prompts them to try.

Symptoms include weight loss; muscle twitching; staggering; and eventually seizures.

BUTTERCUP (Ranunculus)

Buttercups are a common sight and often appear in pastures.  Often your horse will eat around them if there is enough grass. These small yellow flowers cause blistering and ulcers in the mouth if accidentally eaten by your horse.  Usually, this experience stops the horse from eating anymore!

If they do appear in your pasture, make sure there is plenty of grass to eat so the horse can eat around them. If they are in a large quantity, ask for advice on how to remove them safely and responsibly.

HORSETAIL (Equisetum)

As the name suggests, horsetail closely resembles a horses tail and commonly found in pastures and grasslands across the UK.

Unlike most weeds, it is toxic when fresh or dried and as a result grazing land and hay fields must be regularly checked. Over a period of time, repeated ingestion will cause heart and kidney damage.

CHARLOCK (Sinapis Arvensis)

To some, this plant is more well known as wild mustard and it is not a healthy plant for horses to eat.

Charlock likes to grow in heavy clay soils during summer.  It should be removed from pasture to stop a horse eating it in large amounts.

Symptoms can include: frothing at the mouth; bloating; diarrhoea; and breathing problems.

MONKSHOOD (Aconitum)

Monkshood is known as the most poisonous plant in the UK, that is to humans and horses.  However, it is incredibly rare.

Monkshood grows to around 2 to 4 feet tall and native to mountain meadows throughout the northern hemisphere.  When it flowers it produces purple, blue and some species white or yellow flowers.

In appearance, it has violet-blue flowers, which have a ‘monk hood’ hence the name. If you do find monkshood on your land, be very careful about removing the plant as it is very poisonous.

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