Comfrey is a great permaculture plant primarily because of what it can give to the soil as a compost or green manure. It grows fast and can be harvested multiple times over a year and when added to compost or let to rot on the ground it is excellent at increasing microbial activity and adds nitrogen.
To raise comfrey you can sow from seed or propagate via root division in Autumn. Grow in a shady position and regularly water. In a sunny position if you can't keep the water it will wilt and wither, slowly drying up at the ends before passing on to plant heaven.
Choose any average, well drained soil and allow plenty of room for the roots to spread. They generally don't require fertilizing and will survive in pots or the ground. Be aware that they can spread easily via seeding. New growth will appear in spring, with flowers that attract pollinators emerging in summer.
Comfrey is reputedly a great companion for trees such as apple, apricot, peach, pear, plum and nectarine. At times pests such as slugs, snails and aphids will give comfrey some trouble.
Comfrey, once established is a hardy, frost tolerant plant that survives a fair range of climatic and soil conditions.