butterfly and michaelmas daisy

hallo,

my lovely blue daisies are in full bloom and are visited by a lot of tortoiseshell butterflies.
QUESTION
does anyone know on which plant these butterflies lay their eggs? - i shall have to plant some!

thanks, karaman

 

thanks, a useful site - i have many butterflies to ID, many many thanks wiseowl --- karaman

 

@wiseowl is right, nettles.