Success at starting comfrey from seed.

I was successful at germinating the comfrey seeds that I received from Great Britain. My goal is to plant the comfrey around my fruit trees and chop and drop them for mulch. They will also be a food source for free range chickens once my fruit trees are bigger. I already have white clover around the trees, however I wanted a plant to keep the grass down throughout the year and I settled on comfrey as my choice. Any thoughts or ideas on my plans or perhaps suggestions for another nutrient dropping plant would be appreciated.