You will need to be more specific, what do you mean by blue thistle, there are many different species. Some need propagating from seed, others from root cuttings and some by division.
How can you lie there and think of England When you don't even know who's in the team
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Some need propagating from seed, others from root cuttings and some by division.
When you don't even know who's in the team
S.Yorkshire/Derbyshire border
Sorry - meant to add this link
https://www.rhs.org.uk/advice/profile?pid=407
I live in west central Scotland - not where that photo is...