Ragwort (Senecio jacobea) is a common and widespread weed with characteristic yellow flowers and frilly leaves, well known for being poisonous and little else, and an enemy of gardeners, livestock owners and pretty much almost anyone who sees it, earning it nicknames such as 'yellow peril' and 'hooligan'. However, it is also a great plant for wildlife as not only does it provide nectar for insects, there are also many species that feed on it, particularly the Cinnabar Moth, whose yellow and black striped caterpilliars are often seen feeding on the stems. If ingested though, seek medical attention imediately.
The plant is biennial or perennial. The stems are erect, straight, have no or few hairs, and reach a height of 0.3-2.0 metres. The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word "stinking" (and Mare's Fart) arise because of the unpleasant smell of the leaves. The hermaphrodite flower heads are 1.5-2.5 cm diameter, and are borne in dense, flat-topped clusters; the florets are bright yellow. It has a long flowering period lasting from June to November (In the northern Hemisphere).
Pollination is by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20- to 60-headed, flat-topped corymbs. This number of seeds produced may be as large as 75,000 to 120,000, although in its native range in Eurasia very few of these would grow into new plants and research has shown that most seeds do not travel a great distance from the parent plant.
Ragwort can be found along road sides and waste grounds, and grows in all cool and high rainfall areas.
The Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Britain and Ireland it is listed as a weed.