This grower is sure of this plant identification.
A beautiful rosette species with deeply lobed leaves with a maximum height of 1 m. Native to La Gomera where it is becoming increasingly rare due to the encroach of human activity. The plant has large sprays of bright yellow, dandelion like flowers in the spring. The plant makes for an interesting pot or summer boarder plant in a sunny position but needs winter protection (minimum of 7*C)
Milk thistle, Sowthistle
Sonchus genus (Milk thistle). This genus is a member of the daisy family and includes short to tall usually hairless perennials that grow as wildflowers in Britain and Northern Europe.