After the first year, comfrey yields the same regardless of propagation method. Root cuttings are the least expensive method of propagation, and consequently, are used most often. Smaller cuttings will also generate plants, but plants from longer cuttings emerge and establish more quickly. Wilted cuttings should be soaked in cold water until they become firm before planting. Root cuttings develop buds about 3 to 6 weeks after planting, while crown divisions emerge in about 10 days.
Prickly comfrey is propagated by seed in the Soviet Union.
Till the soil so that it is free of perennial and annual weeds, and is level prior to planting. When an area is to be replanted with a different crop, repeated tillage is usually used to remove the comfrey plants. Deep moldboard plowing should be done in September or October, and then followed by tillage with a field cultivator, which will expose roots to the drying and freezing conditions of winter. Herbicides could be used in removing the old plants. Glyphosate was sprayed in June at Rosemount, MN and killed stems and leaves.