Can ragwort really kill your horse?

Ask any horsey person what plant is most dangerous to horses and 9/10 will reply “Ragwort”. But is it so bad that it can kill a horse? There are a lot of myths about this poisonous plant, read on to find out more…

A bit about ragwort first

Classed as a perennial broad-leaved weed, its other names include canker weed, stagger wort or tansy ragwort or, if you speak Latin, Senecio jacobaea L.

Common ragwort is a weed of wasteland and fields that occurs in every county in the UK. Its natural habitat is sand dunes, but it is prevalent on light, low fertility soils and on grassland that is overgrazed. It frequently infests horse’s fields and is often seen along roadsides, railways and on rubbish tips. It is not found on acid peaty soils. Common ragwort does not tolerate regular soil cultivation and is rarely a problem in arable fields.

What is Ragwort?

From May to October, you will see ragwort flowering in tall bunches. It’s a really common weed that grows in the UK around waste ground, roadsides and often, in poorly managed horse pasture. It flourishes when other plant growth is sparse, so if there’s not a lot of grass around, there’s a chance it will get eaten by horses despite its bitter taste when it’s alive.

Germination and life-cycle

Ragwort germinates mainly in the autumn and spring. A seed can germinate anywhere the soil surface is exposed and conditions are favourable. It’s a biennial plant, i.e. it grows from seed and remains in the rosette stage for the first growing season. In the following year, it produces its familiar golden yellow flowers on a stem varying in height from 45 to 75 cm. Flowering normally takes place in late summer, after which most plants die off, leaving a gap for new seedlings.

Reproduction and dispersal

Seed is the principle method of spreading this weed but root fragments are also capable of reproduction. Each plant produces 50,000 - 200,000 seeds over a 4-6 week period from July to September. Ragwort produces feathery type seeds that are dispersed by wind, water, animals, hay and farm machinery. Most seeds are dispersed by wind but mainly fall within 5 metres of the parent. The seeds can remain viable for 5-20 years depending on soil conditions.

Control

The only way to safeguard against loss from ragwort poisoning is to eradicate the weed either by pulling, cutting or chemical control.

Pulling: pulling by hand is recommended where there are only a few plants. It's a good way to control the weed and is best done after a heavy downfall of rain. The pulled plants should then be destroyed or disposed of at a landfill site. If you do decide to pull it out, it is highly recommended that you wear gloves, as the toxins in ragwort can also affect humans through the skin.

Cutting: cutting the plant before the flowers are open prevents the weed from seeding and spreading, but it needs to be done each year for several years and accompanied by good field management. In some cases, cutting can induce development of several heads and the affected plants may persist as perennials. Cut plants should be collected and destroyed as an additional precaution against the risk of seed formation and poisoning.

Chemical control: weed killer works best on ragwort in the rosette stage, i.e. before they flower. Ragwort plants become more palatable after spraying and consequently horses must be kept off treated fields. In these circumstances, spraying should be carried out during late autumn (mid-September to mid-November) or early spring (mid-February to mid-March). Any plants that survive winter spraying are very stunted and weak and can easily be eliminated by a second spraying or by pulling. Check the label before use to confirm the dose rate, and use the highest dose recommended on the label.

What is the problem with ragwort?

When it’s cut or wilted, during hay or haylage making, ragwort loses its bitter taste but none of its toxicity. In fact. it becomes far more palatable and harder for the horse owner to spot, thus posing more of a danger.

Here’s the scientific bit…

Ragwort contains the toxic compounds pyrrolizidine alkaloids. If any part of the ragwort plant, either growing or in its dried form, is consumed by the horse these alkaloids will be absorbed through the gut wall into the bloodstream and then passed through the liver. Unfortunately, the liver is incapable of removing the alkaloids, or rendering them harmless, and as a result the liver cells are damaged. Once these cells are damaged, it’s very difficult for them to regenerate and they die slowly and are replaced with fibrous tissue. Once there are not enough healthy liver cells left to enable the liver to function properly, the liver fails. Liver failure = death.

The effects of ragwort poisoning are cumulative: consuming small amounts over a long period of time is just as dangerous as consuming a large amount in a single session, which is why horses who have eaten ragwort may not show signs until significant liver damage has been done.

What are the signs of ragwort poisoning?

The signs include:

• colic or abdominal pain
• weight loss
• depression
• jaundice
• diarrhoea.

Plus, there are some rather strange behaviours caused by the effect of chemicals on the brain, including pressing the head against the wall, continuous circling or aimless walking, and loss of coordination.

Is there any good news?

Well, yes. But it’s down to you and some hard work to sort it out! The key to success is prevention. In other words, get rid of all ragwort on your field. You must pull out the roots from the ground to prevent it from re-growing, and you are advised to wear gloves and even a face mask to prevent you absorbing the toxins through your own skin or inhaling the pollen. Ragwort must also be disposed of carefully – the best way is to let it wilt, then burn it, keeping it in sealed plastic bags during the wilting process to prevent the seeds spreading.

In summary…

Sadly, yes, ragwort really can kill your horse but it’s not all doom and gloom – look out for the flowers now whilst they are blooming, tog up and get rid of the plants for good.