Oxford ragwort

Senecio squalidus, Oxford ragwort, is a short-lived perennial, biennial or winter-annual herb of the daisy family (Asteraceae), typically forming a much-branched, somewhat straggling plant 0.5–1 m tall. The alternate leaves are glossy, almost hairless and very variable, ranging from undivided to deeply pinnately lobed with narrow, widely spaced segments. From March to December (sometimes nearly year-round in mild urban habitats) the plant produces numerous bright yellow composite flowerheads, each with around 10–14 ray florets surrounding a yellow disc, gathered in loose corymbose panicles. Native to Sicily and the mountains of southern Italy, where it grows on volcanic and rocky substrates, the species famously spread from the Oxford Botanic Garden along the British railway network during the 19th century and is now widely naturalised across Europe, parts of North America and northwest Africa on walls, waste ground and railway ballast.