Milky dashels

A view of Exmoor with a field of MDs in the foreground. There used to be a prize for the tallest milky dashel (Devon thistle) at our local fete. I'd never heard the term before being a blow-in (and not a Devon peasant) but apparently it was named in The Peasant Speech of Devon' by Sarah Hewitt, published 1892, who lists 'dashell' as meaning thistle.