Toxic Plants for Horses in UK Fields This Spring

Spring is here, the grass is growing, and after months of mud and dark evenings most of us are just glad to have our horses back out on decent turnout. But right now it's so important to do a proper walkabout and check of our fields.

Why? Because just as the rest of the trees and plants are starting to bloom, so are some of the most dangerous plants for horses in the UK. Some of them are obvious if you know what you're looking for. Others are easy to miss, especially in their early stages when they blend in with everything else.

It does not matter whether you own your own land or rent. Getting out there and checking is on you. So here is a rundown of the main ones to watch for at this time of year.

Ragwort

You probably already know about ragwort. It is the one that gets talked about the most, and rightly so.

Ragwort contains pyrrolizidine alkaloids, which cause cumulative, irreversible liver damage. That word "cumulative" is the important bit. Your horse does not have to eat a big pile of it in one go. Small amounts consumed here and there over weeks, months, even years, can add up. The British Horse Society warns that ragwort can damage the liver over a prolonged period, eventually leading to severe disease and even death. The really cruel part is that by the time you actually see symptoms, the damage is usually already done. A horse's liver can keep functioning until roughly 70% of it is destroyed, so there is often no warning at all until it is far too late.

Right now in April, ragwort is in its rosette stage: flat clusters of dark green, crinkly edged leaves sitting close to the ground. A lot of people do not recognise it until the yellow flowers appear in summer, but by then it has set deep roots and possibly already gone to seed. The spring rosettes are actually the easiest stage to deal with. Get out after a good spell of rain when the ground is soft, use a ragwort fork, and pull the whole thing up by the root. Wear gloves, bag it and remove it from the field entirely.

And this is the bit people forget: do not just leave pulled ragwort lying in the field. As it wilts and dries out, it actually becomes more palatable to horses while staying just as toxic. World Horse Welfare points out that younger ragwort plants can also taste less bitter than mature ones. So they are more likely to eat it dead than alive, and more likely to nibble young rosettes than you might think.

Ragwort is covered by the Weeds Act 1959 and the Ragwort Control Act 2003, so landowners have a legal obligation to control its spread, particularly within 50 metres of land used for grazing. DEFRA's Code of Practice on How to Prevent the Spread of Ragwort sets out the framework, and the British Horse Society has guidance on what to do if ragwort on neighbouring land is affecting your horses.

Sycamore Seedlings

If ragwort is the most talked about danger, sycamore is the one that scares people the most, a rightly so.

Atypical myopathy is a severe muscle disease caused by a toxin called hypoglycin A, found in sycamore seeds, seedlings, and leaves. Most people associate the risk with autumn, when the helicopter seeds are falling everywhere, but spring is the other high risk window. This is when last autumn's seeds germinate and send up small seedlings across your pasture. The British Equine Veterinary Association (BEVA) warns owners about this spring risk, and in 2023 flagged what they described as an "explosion" in sycamore seedling growth causing a rise in cases.

Here is the thing that catches people out: mowing does not make the seedlings safe. Neither does spraying them with herbicide. Research published in the Equine Veterinary Journal (Gonzalez-Medina et al., 2019) confirmed that the toxin stays active in sycamore seedlings even after mowing, herbicidal spraying, or storage in hay and silage. If you mow an area with sycamore seedlings, you have to collect every last cutting and remove them from the field. Otherwise your horse could eat the mown debris and still be poisoned.

Those helicopter seeds can travel up to 200 metres on the wind, too. So even if you do not have a single sycamore on your land, seedlings could be popping up from seeds that blew in from next door. The British Horse Society stresses this point and recommends checking neighbouring areas as well as your own fields.

The survival rate for affected horses sits somewhere around 30 to 40%, according to figures from the BHS. The disease can develop within hours, and young horses seem to be more vulnerable, especially those on bare or overgrazed pasture where they end up foraging on whatever they can find. In 64% of atypical myopathy cases reported to the Atypical Myopathy Alert Group between 2006 and 2019, the pasture had minimal grazing available.

Walk your fields. Pull seedlings up by hand. Fence off areas near sycamore trees. And make sure there is enough decent forage available so your horse is not tempted to graze on things it should not be eating.

Buttercups

Buttercups are so common that most people barely think about them. They start popping up around now and they will be everywhere by May.

Fresh buttercups contain a compound called ranunculin that can irritate the mouth and digestive system. Most horses avoid them because they taste bitter, but on overgrazed land where there is not much else to eat, some will munch through them regardless. The good news is that dried buttercups lose their toxicity, so they are not a worry in hay.

The bad news? If your fields are carpeted in buttercups, that is telling you something. Heavy buttercup growth is usually a sign of poor soil, low pH, compaction, or overgrazing. So if you're seeing a lot of buttercups in your field then it's worth getting your soil tested and looking at whether liming or reseeding might help push the balance back towards decent grass.

One thing to watch for: horses who graze in buttercup heavy fields sometimes develop soreness around the muzzle and lower legs where the plant has been brushing against their skin. If you notice redness or irritation in those areas, move them to a cleaner pasture and you should see this clear up fairly quickly.

Foxglove

All parts of the foxglove plant contain cardiac glycosides. The Blue Cross notes that as little as 100 grams of foxglove can prove fatal to a horse, and the BHS warns that death from foxglove poisoning can occur within just a few hours.

The flowers do not appear until summer, but the leaf rosettes are growing strongly right now. They are quite distinctive: large, soft, slightly furry leaves in a low cluster, usually found in shady spots, along woodland edges, and in the scrubby corners of fields that do not get mowed or grazed hard.

Horses tend to avoid fresh foxglove because of the taste. The real risk is when it ends up in hay or haylage, as it is more palatable once dried but still just as dangerous. If you are cutting your own hay, walk the fields first. Pull foxglove out before it has a chance to flower and seed.

Hemlock

Hemlock is a nasty one, partly because it looks so much like cow parsley that a lot of people walk straight past it.

Both plants have the same sort of ferny, divided leaves and clusters of small white flowers. But hemlock has smooth, hollow stems with distinctive purple or reddish blotches, especially near the base. Cow parsley stems are slightly hairy and green all over. That purple blotching is your main clue.

The roots and seeds of hemlock contain neurotoxins that cause respiratory paralysis. It is fast acting and even small amounts can kill. You will usually find it in damp spots such as ditches, riverbanks, wet field margins and boggy corners.

If you are not confident telling the two apart, it is genuinely worth spending half an hour learning. The British Horse Society has good identification guides, and so do most county wildlife trusts. Once you have seen the difference side by side, you will not mix them up again.

Hogweed

There are two types of hogweed in the UK, and they are quite different in terms of the risk they pose.

Common hogweed is everywhere. Hedgerows, field edges, roadside verges. It is already growing strongly by April, with big, lobed leaves and thick, hairy stems. The plant contains furanocoumarins, which cause photosensitisation. If a horse eats it or the sap gets on their skin, sunlight makes the reaction much worse. You can end up with painful blistering, burns, and raw patches, particularly on lighter or pink skinned areas. A lot of people see common hogweed as just a boring hedgerow plant, but it can cause real problems if your horse has access to it.

Giant hogweed is a completely different level of danger. The sap causes severe chemical burns on contact, in horses and humans alike. Sunlight intensifies the reaction massively. It is classified as an invasive non native species under the Wildlife and Countryside Act 1981, and if you find it on your land you should take it seriously.

Giant hogweed likes damp ground. Riverbanks, ditches, wet field edges. By midsummer it can reach five metres tall, but the young growth appearing now is much smaller and easier to overlook. The two species can look quite similar when young, though giant hogweed tends to have more sharply pointed leaf segments and develops purplish red blotches on its stems as it grows.

If you think you have found giant hogweed, do not touch it with bare skin. Wear full protective clothing to remove it, or better yet, report it to your local authority. If your horse does come into contact with the sap, keep the affected area out of direct sunlight and ring your vet straight away.

Horsetail

Horsetail is an odd looking plant. In spring, you will see pale brown, cone topped shoots poking up through the soil. Later in the year, these give way to green, fir tree shaped fronds.

It is toxic to horses. It causes something similar to a thiamine (vitamin B1) deficiency, which affects the nervous system. Fresh horsetail is not very palatable, so most horses leave it alone in the field. The bigger danger is it ending up in hay, because it stays toxic when dried.

The frustrating thing about horsetail is how difficult it is to get rid of. The roots go incredibly deep and it spreads aggressively. Pulling it up by hand is largely pointless. Long term pasture management, better drainage, improved soil fertility, are the best solutions. And if you are buying in hay, give it a good look over for horsetail stems before you feed it, especially if it was cut from wetter ground.

Bracken

Bracken is not a sudden killer. It is more of a slow burn.

Horses who eat it regularly over a period of time can develop neurological problems: staggering, loss of coordination, muscle spasms. Like horsetail, the toxic compound destroys thiamine. You will mostly find bracken on hillsides, heathland, and rough acidic ground. Most horses do not seek it out, but those on sparse moorland grazing might eat it when there is not much else on offer.

Right now, young bracken fronds are uncurling from the ground in their characteristic fiddlehead shape. If it is present on your grazing, fencing it off is the simplest answer. Repeated cutting over several years can weaken it, but it takes real commitment.

Bluebells

This one surprises people. Bluebells contain glycosides that can cause digestive problems and, in larger quantities, more serious effects.

They are at their peak right now, carpeting woodlands and shady hedgerows from late March through to mid May. Most horses will not encounter them in open pasture, but if your fields border woodland or you ride through wooded areas regularly, it is something to be aware of. The risk is low in most situations, but keeping horses out of dense bluebell patches makes sense.

What to Do if You Suspect Poisoning

If your horse is showing anything unusual, whether that is lethargy, reluctance to move, stiffness, colic like signs, loss of appetite, or just "not being right", get your vet involved quickly. With plant poisoning, early intervention can make a real difference. Do not wait and see.

If you can, take a photo of whatever you think the horse might have eaten. That information can save your vet a lot of guesswork.

Keeping on Top of Your Fields This Spring

None of this has to be overwhelming. A good field walk once a week through spring is one of the best things you can do. You are looking for ragwort rosettes, sycamore seedlings, anything unfamiliar along your fence lines and hedgerows, and anything suspicious in the wetter corners. There's also apps out there which scan and identify plants and, although they're not completely reliable, they can act as a second pair of eyes on anything you're not sure of.

Pull or dig out toxic plants before they flower and seed. Bag them up and take them out of the field. Do not leave pulled ragwort or foxglove lying around for your horse to find later. The GOV.UK guidance on injurious weeds is clear that landowners can face enforcement action if harmful weeds are allowed to spread onto grazing land, so staying on top of this is not just good practice, it is your responsibility.

If your pasture is thin, full of weeds, or showing signs of overgrazing, get your soil tested. Acidic, nutrient poor ground is where ragwort and buttercups thrive. A bit of lime and some decent grass seed can shift things back in the right direction over time.

Check any hay or haylage you buy. Ragwort, foxglove, horsetail, and hemlock can all end up baled without anyone noticing.

And fence off anything you are not sure about. Sycamore trees, suspect hedgerows, damp areas with plants you cannot identify. Better safe than sorry.

Spring is a brilliant time of year for horses and their owners. A bit of knowledge and a regular field walk is all it takes to make sure your horse can enjoy it safely.

Useful Resources

If you want to dig deeper into any of the plants mentioned in this post, or need help identifying something you have found in your field, these are some of the best places to start:

British Horse Society: Poisonous Plants - Detailed guides on identifying and managing toxic plants in horse pasture, including ragwort and sycamore.

British Horse Society: The Dangers of Ragwort - Everything you need to know about ragwort identification, removal, and your legal responsibilities.

British Horse Society: Atypical Myopathy - The BHS guide to sycamore poisoning, including risk factors and prevention advice.

Blue Cross: Poisonous Plants Horses Should Avoid - A practical overview of common toxic plants with identification tips and symptoms to watch for.

Blue Cross: Sycamore Poisoning in Horses - Guidance on atypical myopathy, including how to reduce the risk on your pasture.

World Horse Welfare: Ragwort - Practical advice on dealing with ragwort in horse paddocks, including removal and disposal.

GOV.UK: Stop Ragwort and Other Harmful Weeds from Spreading - The official government guidance on your legal obligations under the Weeds Act 1959, including how to report problems on neighbouring land.

DEFRA: Code of Practice on How to Prevent the Spread of Ragwort (PDF) - The full code of practice for ragwort control, covering risk assessment, removal methods, and disposal.