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Common UK Plants & Trees Poisonous to Horses
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Common UK Plants & Trees Poisonous to Horses



I found it quite difficult to find a list of commonly found poisonous plants in the UK that are poisonous to horses, so I thought this may be a useful article for this time of year as we turn our horses out onto summer grazing.

Symptoms of plant poisoning

Poisoning can kill a hours within a matter of hours, if you suspect that you horse has eaten a poisonous plant contact your vet immediately for advice.

There are many different symptoms of poisoning that vary depending on the type and quantity of harmful substance that the horse has ingested.

Symptoms include:

  • Unusual pupil contraction/dilation
  • Altered breathing, speed, ease, rhythm and sound
  • Narcosis - sleepiness or unconsciousness
  • Colic like symptoms
  • Sweating
  • Diarrhoea
  • Altered heart rate
  • Frothing at mouth
  • Mouth blisters
  • Lack of co-ordination
  • Convulsions
  • Jaundice This list is not exhaustive.


Some plants have a cumulative effect, this means that each time the horse eats the plant the effects build up and it may be some time before you notice the effect. Your horse may appear to eat the plant without effect, but this is not the case.

Common poisonous plants & trees and their effects

  •  Ragwort

Horses are particularly susceptible to ragwort poisoning as it contains toxins that result in liver failure and even death.

Ragwort has a bitter taste and is rarely eaten by horses when it’s growing, but when wilted or dried it becomes more palatable – but it’s still poisonous, so hay should not be made from fields containing ragwort. If you notice ragwort in hay you hay it must not be fed to horses.

Eating just 1-5kg of ragwort over a horse’s lifetime may be fatal, so it’s vital that horse owners know how to identify ragwort and remove it.

Ragwort takes two years to fully grow and flower, from a dense rosette of leaves in the first year to producing bright yellow flowers on 30-100cm woody stems in the second.

Each plant produces thousands of seeds that are dispersed widely by the wind and can survive in the ground for decades, So it is particularly important to removes mature plants before they go to seed.  Ragwort thrives on poor grazing and wasteland.

The control of ragwort comes under two government acts, The Weeds Act 1959 and the Ragwort Act 2003. Under these, government authorities can serve clearance notices to the owners / occupiers of land containing ragwort. A code of practice to prevent the spread of ragwort is available from DEFRA.

If you see ragwort you should uproot, remove and burn it. Good pasture management and using herbicides is important to control the growth of this weed.

Spray it when the plant is at the rosette stage rather than waiting for the stem to appear, and don’t try to mow or cut it as this actually makes it grow more.

Both Defra & the BHS produce a downloadable leaflet regarding the safe removal and disposal of ragwort.

Link to Defra Leaflet


Link to BHS Leaflet


  •  Foxglove

Horses won’t normally eat fresh foxglove but it’s more palatable in hay and just 100g could prove fatal after only a few hours.

  • Deadly Nightshade

Poisoning form nightshade is not normally fatal but can cause narcosis, dilation of the pupils and convulsions.

  •  Buttercups

These are poisonous when fresh but a horse would need to eat large amounts. Seek professional advice on spraying. Dried buttercups are harmless in hay.

  •  Oak (acorns)

Oak trees pose a particular threat as they drop their acorns in the autumn.

Acorns are relished by many horses and can lead to severe colic and poisoning if eaten in large quantities.

Acorns should be collected up or horses moved to alternative grazing in the autumn.

  • Yew

Yew is common in gardens, and the fallen leaves and berries are as lethal as the fresh plant – so be careful of these being blown into your field, even if the hedges are fenced off. Just 0.5kg can be fatal.

  •  Privet

This is common in gardens so be careful of neighbours’ hedges and the possibility of people dumping cuttings in the field. Box privet is the most dangerous.

  • Rhododendron

Very small quantities can cause a horse’s respiratory system to fail.

Protecting your horse from poisonous plants

  • Different methods are appropriate for different types and quantity of plant. Some of these plants can be harmful to humans too, even if you do not eat them directly. If in doubt use protective gloves when handling poisonous plants and wash your hands afterwards.
  • Remove individually - remember to protect yourself from the harmful effect of the plant if necessary or seek professional assistance in the case of removing trees, and be aware of any protection order that may exist. Remember to remove & dispose of plants in the correct way
  • Fence off so the horse does not have access to the plant or tree. Make aware of poisonous parts of the plant or tree can blow or fall into your horses pasture
  • Spray with herbicide - follow the guidelines on individual herbicides, including excluding horses from the pasture for a period after spraying.

Be aware that many ornamental plants can be poisonous so horses should not be allowed access to these directly or by reaching over the fence. Do not compost garden prunings in your horses’ pasture.

Image Vacker "Stånds" fara by Per Egevad, Flickr

© Per Egevad


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