Ragwort 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 on the Defra website (https://www.gov.uk/government/uploads/system/uploads/attachment_data/fil...). Foxglove 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 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. Acorns 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. Yew 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. Privet 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. Rhododendron 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. 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. Linseed Is another name given to the Flax plant. The Flax plant has five pale blue petals with brown seeds within and grows to approximately 1 meter in height. These seeds are poisonous. Horses Symptoms Symptoms of linseed poisoning are a rapid heart beat, breathing difficulties, excessive salivation and difficulty in standing and in coordination. Linseed can be found throughout much of Europe. Bracken Bracken is a type of fern which commonly grows between two and six feet high. Bracken dies back during the autumn and cold winter months and starts to come through again in the spring and summer months. Horses Symptoms When Eaten Bracken can cause a deficiency in vitamin B1, symptoms can include a lack of appetite, general weakness and disorders of the nervous system. Bracken Can Be Found Bracken can be found worldwide, especially in good draining areas such as woodland and hill tops where it is especially successful. Iris The Iris can be a number of different colours. Horses Symptoms Iris poisoning can cause digestive upsets and general weakness with a rise in the horses temperature. The Iris Can Be Found Iris can be found throughout United Kingdom, North America and parts of Europe. here to edit.