A southern European ragwort, Senecio squalidus, which escaped from Oxford Botanic Garden and is now naturalized on waste ground, railway tracks, etc., in many parts of Britain.
Origin
Late 19th century; earliest use found in William Miller (c1831–1898).
Definition of Oxford ragwort in US English:
Oxford ragwort
noun
A southern European ragwort, Senecio squalidus, which escaped from Oxford Botanic Garden and is now naturalized on waste ground, railway tracks, etc., in many parts of Britain.
Origin
Late 19th century; earliest use found in William Miller (c1831–1898).