Comfrey is harvested for it's roots and leaves. They are both harvested at different times. The plant energy is in the roots during the late fall and winter months, so this is the best time for harvest.
The leaves of the plant can be harvested any time during their growth, the spring being the optimal time for gathering. This makes sense, because the energy of the plant is vigorously making new growth.
When storing roots or leaves, it is important to prepare the herbal parts accordingly. The roots are scrubbed vigorously, and then chopped into manageable sizes for drying. Once the roots are dry, they are like rock and you will literally be unable to chop or cut them.
Small pieces that have been cut and dried can be ground in a coffee grinder.
Leaves must be dried with care. They are fleshy and fuzzy, making them a little harder to dry. Keep them in a single layer and flip them often, to be sure that there is no mold present. Once the leaves are completely dry, store them in an airtight container, out of direct sunlight.
A Word Of Caution About Internal Use:
There has been studies done that show the possibility of comfrey being a carcinogen. One study showed rats fed 8% of their diet in comfrey, developed liver cancers and others showed liver problems.
It is common for many herbalists (especially the family herbalist) to recommend NOT using comfrey internally, because it is still unclear about the overall safety of comfrey being ingested. This is sound advice.
Although the jury is still out about comfrey use internally, it is unparalleled for external use.
All About Comfrey:
Useful for skin healing, and as a poultice for bruises and sprains and sores. Add comfrey to your skin healing salves, remembering that it truly is a powerful skin regenerator, and caution needs to be used that the wound is already healing before applying a salve that may trap infection under new skin. Use a wash of comfrey to help kill bacteria and speed healing of infected wounds, the difference being that a wash is simply a water based application and not a waxy or grease based herbal. This means that there will be nothing to trap and hold infected cells in the wound.
Use comfrey for eczema and insect bites, athlete's foot and dry, cracked feet or hands.
Finally, never discount comfrey as a stunning ornamental herb! It is somewhat large, so allow it to sprawl and display it's beautiful flowers all season long. It also spreads aggressively, so plant it in sunken pots, or somewhere that you can enjoy the natural beauty, but not need to dig it up completely. I hope you grow and enjoy comfrey. It is an often maligned herb that is actually invaluable in the home medicine chest.