Comfrey (also comphrey) is a common name for plants in the genus Symphytum.Comfrey species are important herbs in organic gardening. It is used as a fertilizer and as an herbal medicine.The most commonly used species is Russian comfrey Symphytum × uplandicum, which is a cross or hybrid of Symphytum officinale (Common Comfrey) and Symphytum asperum (Rough Comfrey).ature comfrey plants can be harvested up to four or five times a year. They are ready for cutting when about 60 cm (24 in) high, and, depending on seasonal conditions, this is usually in mid-Spring. Comfrey will rapidly regrow, and will be ready for further cutting about 5 weeks later.