I have successful white comfrey in the front garden with hundreds of flowers. Presumably the flowers contain the seeds. Can I grow new white comfrey in the back garden by planting large numbers of fallen flowers? I wait for them to fall rather than picking them. I also find on the ground little "brown envelopes", which appear to contain seeds, see sixth picture here http://wildflowerfinder.org.uk/Flowers/C/Comfrey(White)/Comfrey(White).htm
Presumably I should plant these as well.