Poisonous plants to remove from a horse's field

Poisonous plants to remove from a horse's field

Health & Safety

Summer is often viewed as the easy period for horse owners, as they can turn their equines out to enjoy the sun and graze for long hours every day. If only it were that simple! As well as making sure the paddock is kept free of droppings, that grazing is rotated, and fences aren’t damaged, an owner must keep watchful over every acre they roam. Pasture land is prone to the influx of weeds the same as garden borders. In the UK, a number of our weeds and trees are extremely dangerous to horses. An owner must be aware of what to look out for, how to remove them, and be watchful of possible symptoms. Even areas around the yard and areas outside of fences should be checked, to ensure seeds do not spread over the season.


Ragwort is a slow killer, and in many cases you won’t know your horse has eaten it until too late. It is common in pastures, growing up to 2 metres high when it flowers. It is instantly recognisable due to its bright yellow flowers. If a horse ingests it, it will gradually start to destroy the liver. A poisoned horse will lose weight despite eating normally, get extreme sunburn, go blind and eventually collapse if it isn’t caught early. The only way to protect your horse is to remove the weed completely from your field. Pull it up by the roots and burn the plant, so no pollen can spread. Make sure you contact Defra who can also advise on other methods to protect your horse. It is a resilient plant, and will nearly always grow back and spread to other pastures.


Named after its resemblance to a horse’s tail, it is common in pastures and meadow land across the UK. Unlike a number of weeds, it is toxic when fresh and dried – as a result pastures and hay fields must be checked regularly. If eaten over a long period of time it will cause heart and kidney damage.


Common across England, these small flowers don’t just tell you if you like butter. If accidentally eaten by a horse, they will cause blistering and ulcers in the mouth. This will usually stop a horse eating them further, but if nothing else is available they will continue to ingest them until it causes a life threatening seizure. 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, look at how you can remove them safely.


Named due to its toxicity to cattle, it is also poisonous to horses. The roots of the plant are the only toxic part, containing Cicutoxin. Although it is not common for horses to eat this part of a plant, accidents do happen. When eaten it can cause convulsions, colic and dilated pupils. If the horse survives the first few hours, he is likely to be fine in a few days.

Bracken Fern

Found in a number of well-drained pastures and moors, this fern can kill if repeatedly eaten over a long period of time. Most horses and ponies will avoid it, but as it is a fern dry seasons can tempt horses out of desperation. Symptoms include: weight loss; muscle twitching; staggering; and eventually seizures.


More well known as Wild Mustard, it is not a healthy plant for horses to be exposed to over a long period of time. Growing in heavy clay soil during the summer months, 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.


This small evergreen tree is extremely dangerous to most livestock, with only 8ozs being enough to kill a horse in 5 minutes. The bark and leaves (fresh or dead) are lethal to a horse if eaten. The symptoms of a poisoned horse are: trembling; muscle weakness; slow or irregular heartbeat; and, convulsions. The alkaloids in the plant destroy the heart muscles and will eventually lead to a heart attack. If diagnosed quickly, vets can use atropine to stabilise the heart and detoxify the animals system. No animal should be placed in pasture near yew trees.


Although horses love to eat oak leaves and acorns, they cause a number of digestion problems which can kill a weak horse. Symptoms will start with a loss of appetite, and then the poison will start to attack the bowels causing constipation, diarrhoea, and colic.


Used to create garden borders, it cannot be digested safely by a horse. Symptoms of privet poisoning are: staggering; diarrhoea; convulsions; and paralysis. Within 4 to 48 hours after eating the privet, a horse will die if a vet is not brought in to administer care. Privet hedges should be planted out of the reach of horses, and avoided on rides if you choose to stop for a pick of grass.


Common to many an English country garden, this beautiful flower is not usually found in pasture. It has been known however to accidentally get harvested with hay. Check your hay quality regularly, and also talk to your hay producer to make sure they are eradicating any foxglove found in their fields. If eaten in hay, symptoms will include diarrhoea, abdominal pain, convulsions and heart failure.


A common weed found in pasture, it is poisonous to all forms of livestock. Like ragwort, it contains alkaloids – this form cause respiratory paralysis. Many animals have died when it has become accidentally mixed into forage. Hemlock should be removed and burnt if found in a field during the Spring.


Possibly the most poisonous plant in the UK, it is also incredibly rare. Owners should be aware of its appearance however, just in case it appears in your field. It has violet blue flowers, which have a monk hood. If you do find some, be very careful removing them as they are also poisonous to humans.



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