My introduction to comfrey, more than 30 years ago, remains a wonderful memory.
I was a newbie farmer and full of enthusiasm. I arrived as a volunteer at Harvey Sacarob’s organic farm in Honaunau around 6:30 a.m. Standing in the dim early morning light with a few other bleary-eyed volunteers, we watched sunlight creep up the terraces on the hill at the back of the farm. A row of comfrey plants fronted each terrace of vegetables. As the golden light gradually buttered the ridge, it touched each row of comfrey in its path. The plants sparkled and twinkled as the sunlight hit the dew caught in their fuzzy leaves. I wept at the sight and fell in love with comfrey that day.
Comfrey is definitely a plant worthy of love. Its numerous features make it an essential plant for every garden. At Harvey’s farm, the vegetable terraces were well protected against erosion by the presence of comfrey. He also used the comfrey leaves to add nutritional value to his compost or to place on the soil as mulch and a nutrient enhancement.
Comfrey is a member of the Boraginaceae (Borage) family and is related to the herb borage as well as the indigenous native Hawaiian kou and an endemic variety of hinahina. Like borage, comfrey leaves are covered in tiny hairs giving them a fuzzy look and feel. Beyond the botanical classification, however, comfrey has very few similarities to its other family members.
True comfrey (Symphytum officinalis) has a long history in temperate as well as tropical locations as a useful plant and medicinal herb. It was traditionally known as “knitbone” or “boneset” and was used as a healing tea or poultice for injuries including broken bones. Recently, scientists have found some comfrey varieties contain pyrrolizidine alkaloids, which may be toxic to the liver. The Food and Drug Administration now advises that comfrey only be used externally.
Evidently, some varieties contain very little of this alkaloid and offer a highly nutritional soil amendment. The variety named Russian Comfrey Blocking #4 (Symphytum x uplandicum) is probably the best choice for low toxicity and high nutrients. Its leaves are particularly high in N-P-K and can be harvested often to be used as mulch, cut up to use as green manure or added to enrich compost. The seeds of this variety are sterile however, so the plant can only be propagated vegetatively.
In its native habitat in temperate zones of Europe and Asia comfrey grows in damp, grassy locations, often on the banks of rivers. True comfrey does produce seeds and can spread easily becoming somewhat invasive. The Russian hybrid’s sterile seeds make it easier to control.
All comfrey varieties can be propagated by division. Regular division can reduce the size and crowding of your comfrey plants. Every few yours you may want to divide the plant(s) and their roots into several starter plants. Slice through the plant with a sharp knife or shovel creating small starter plants. Cut back most of the leaves and plant the starters in a place that gets at least a half day of sun. Young plants will do best in soil that drains sell and gets regular watering. Once established, comfrey is somewhat tolerant of dry spells.
True comfrey can be grown from seed, but requires a chilling period to germinate. This can be achieved by refrigerating the seeds for several months in the winter. The seeds may also be very slow to germinate, sometimes taking more than a year to sprout. If you can find gardeners willing to divide their plants, root division may be the way to go. Otherwise, look for young plants in a nursery.
Comfrey is often grown as an attractive garden addition as well as for its many other benefits. The plant constantly produces upright green leaves that form an attractive clump several feet wide and between two and three feet high. The deep green leaves can be harvested throughout the year for nutritious biomass for the garden as well as to use for healing purposes
Seasonally comfrey plants will put up thin, hairy stalks that hold clusters of small bell-shaped flowers in various shades of blue or purple. These pretty flowers attract bees and other pollinators to the garden. Only true comfrey produces viable seeds following flowering, however.
Comfrey’s deep root system can grow up to ten inches into the soil. This is what makes comfrey such a good choice for holding soil on a slope to prevent erosion. The roots are also valuable medicinally.
With so many positive features and uses, you can see why I love the plant and recommend that it be planted in every garden.
Diana Duff is a plant adviser, educator and consultant living part time in Kailua-Kona.