The plant is astringent, diaphoretic, diuretic, emmenagogue and expectorant. The plant is harvested as it comes into flower and is dried for later use. Use with caution, when applied internally it can cause severe damage to the liver. See also the notes above on toxicity. An emollient poultice is made from the leaves. The juice of the plant is cooling and astringent, it is used as a wash in burns, sores, cancerous ulcers and eye inflammations. It makes a good gargle for ulcerated mouths and throats and is also said to take away the pain of a bee sting. Caution is advised here since the plant is poisonous and some people develop a rash from merely touching this plant. A decoction of the root is said to be good for treating internal bruises and wounds. A homeopathic remedy is made from the plant. It is used in the treatment of dysmenorrhoea and other female complaints, internal haemorrhages and other internal disorders.
A good green dye is obtained from the leaves, though it is not very permanent. A yellow dye is obtained from the flowers when alum is used as a mordant. Brown and orange can also be obtained.
Succeeding on all but the poorest soils, this plant is a declared noxious weed in Britain spreading freely by seed. It should not be cultivated other than in controlled conditions for scientific research. Ragwort can be eradicated by pulling it up just before it comes into flower, or by cutting it down as the flowers begin to open (this latter may need to be repeated about six weeks later). Ragwort is a good food plant for the caterpillars of many butterfly and moth species, and is one of only two species that provide food for cinnabar moth caterpillars.
A noxious weed, it does not need any help in spreading itself about.