You can also transplant divisions of existing plants. Pieces of the root will often sprout, so once planted, comfrey is very hard to eradicate. It can also spread to invade adjacent plantings. Handsome variegated forms have white-edged leaves. Or handpick and drop them into a container of soapy water.
Some forms have leaf variegation, too.
It grows 2 feet high. It reaches 6 feet high.