A short-lived perennial herb of waste places, walls, railways, cinders, roadsides and gardens, where it is often thoroughly established on well-drained soils. Lowland.
This species was first recorded in 1794 as an escape from Oxford Botanic Garden. It was recorded at scattered localities until the 1850s, but spread rapidly after reaching the railway in Oxford in c. 1879. Since the 1962 Atlas its range has increased and it has spread off railways into other habitats. In Ireland it was naturalised in Cork city by 1845 but its spread from there has been relatively slow.
S. squalidus appears to have arisen in cultivation in the Oxford Botanic Garden (Abbott et al., 2000).
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