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Nine poisonous plants horses should avoid

With some plants and trees being poisonous, and sometimes fatal, to horses, it’s important you know their names, can recognise them, and are aware of the places they may grow, so you can keep your horse safe. Here are the nine most common poisonous plants to watch out for…



While ragwort has a bitter taste and is rarely eaten by horses when it is growing, when it is wilted or dried it becomes more palatable. This plant contains toxins that result in liver failure and even death, so hay should not be made from fields containing ragwort. Eating just 1-5kg of the stuff over a horse’s life time may be fatal.


Ragwort thrives on poor grazing and wasteland, and each plant produces thousands of seeds that are dispersed widely by the wind. Local authorities have legal power to order land owners to clear land containing the weed, and a good guide to identifying it is available here.


It 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. Ragwort thrives on poor grazing and wasteland, but each plant produces thousands of seeds that are dispersed widely by the wind.


Ragwort should be controlled by good pasture management, the use of herbicides or manual control when it should be uprooted, removed, and burned. Spray it when the plant is at the rosette stage and don’t wait for the stem to appear. Mowing and cutting ragwort isn’t a good idea as it will make it grow back more quickly.




Horses will not normally eat fresh foxglove but it is more palatable in hay and just 100g could prove fatal. Symptoms of foxglove poisoning include, contracted pupils, convulsions, breathing difficulties and death after only a few hours.


Deadly nightshade

Despite its name, poisoning from nightshade is not normally fatal to horses but can cause unconsciousness, dilation of the pupils and convulsions.



Buttercups are poisonous to horses if eaten fresh, but a horse would need to eat large amounts to die from eating them.

Seek professional advice on spraying to remove from grazing areas. Dried buttercups are harmless in hay. 



Oak trees pose a particular threat to horses when 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.

Collect the acorns up, or move horses to a place without oak in the autumn.  



Is common in gardens, and the fallen leaves and berries are as lethal to your horse as the fresh plant – so be careful of fallen leaves and berries being blown into your field, even if the hedges are fenced off. 

Just 0.5kg can be fatal, with the horse falling into an insensitive state similar to sleep.



Is also 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, as eating even small quantities can kill a horse.



Very small quantities of this are highly toxic to horses, causing death by failure of the respiratory system.


Sycamore, maple and other acers

This is known as seasonal as it is thought that the helicopter seeds in autumn, and the saplings in spring, contain Hypoglycin-A that causes atypical myopathy in horses. Find out more about atypical myopathy.

Symptoms include muscular stiffness, reluctance to walk, muscle tremors, sweating, depression, high heart rate, dark urine (reddish in colour). Your horse may appear weak and may have difficulty standing, breathing difficulties, but may still want to eat. Call your vet as quickly as you can.

Find out how to prevent your horse from meeting these poisonous plants here.

— Page last updated 11/05/2022