Anonymous

Do you mean specifically comfrey? or how to harvest roots in general? The idea is of harvesting roots is simple enough - dig up the plant and take the roots. There is however, a lot more that a considerate person should think about.

For example:
1) Usually you are killing the plant when you do this

2) the plant may be endangered or at-risk due to over-harvesting

3) the local plant population may not be ‘willing’ to let you take it

4) harvesting, or wildcrafting for many is a spiritual practice of taking a life and assuming it into another. Offerings are often left as a sign of gratitude. 

I really recommend this book for anyone interested in herbalism: The Herbal Medicine-Maker’s Handbook by James Green. It covers all the basic ways to prepare herbs, as well as a wealth of info on how to use them.