What is ragwort?
Ragwort (Senecio jacobaea) is a British native biennial wildflower. It grows to around 90cm and bears clusters of yellow, daisy-shaped flowers in summer and early autumn. Its has finely divided, toothed leaves.
Ragwort's value to wildlife
Ragwort is an important source of food to a huge range of insects – around 35 species rely completely on ragwort, and there are hundreds of others, including the beautiful cinnabar moth, for which ragwort is an important source of larval food, pollen and nectar. Birds eat the seeds.
Is ragwort poisonous?
Ragwort is mildly poisonous, thanks to toxins called pyrrolizidine alkaloids. These can be advantageous to wildlife – both the adults and caterpillars of the cinnabar moth are brightly coloured to warn predators against eating them, as they ingest the toxins, which remain in their bodies and make them unpleasant to eat.
However, ragwort can be poisonous to mammals, particularly horses, which can develop liver poisoning if they eat ragwort in large quantities (thought to be between five and 20 per cent of a horse's bodyweight). Other farmed animals, including cows, may also be affected by ragwort poisoning, although sheep and goats are considered less at risk.
Because ragwort contains toxins, animals avoid eating it. In summer, you may spot horses in paddocks where the grass is short but the ragwort grows tall. This is because the horses know ragwort tastes unpleasant and will eat around it. They usually only ingest it by accident, usually when it's present in dried winter hay mixes. However moulds can also form on winter hay mixes, which are also detrimental to horses' health.
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Ragwort could potentially harm humans but, as it's only mildly poisonous, you would need to eat an enormous amount for it to harm you. What's more, there have been no cases of ragwort poisoning in humans in the UK. It's completely safe to touch ragwort – the mild toxins can be absorbed through human skin, but these do not pose any risk to human health.
Ragwort in gardens
In gardens ragwort is usually regarded as a weed, although wildlife gardeners, who appreciate its huge value to insects and birds, often leave areas of ragwort to thrive. It's well-suited to growing in wildflower meadows.
How to control ragwort
Ragwort produces masses of seed which are carried on the wind. It can therefore spread quickly, and if you live near a horse paddock it's polite to deadhead the flowers before the seeds develop, to prevent it spreading out of your garden.
However, if you really don't want ragwort growing in your garden, you can simply pull it out of the ground. Ragwort is easy to pull and can then simply be composted.