Widely adapted and easy to grow, comfrey (Symphytum species) originated as a woodland wildflower of Europe and Asia. Various medicinal uses for comfrey date back 2,400 years, and no wonder. If you cut a stem and touch it to your tongue, you can taste a tingle, as if the sap is alive. We now know this is due in part to the presence of pyrrolizidine alkaloids, which can be toxic to the liver when eaten by people and other animals. So what? Without ever tasting a leaf, you can use comfrey to make your garden more beautiful and productive. After working with this talented plant for 30 years, here are what I think are the seven best uses for comfrey.
1. Plant Up Shady Areas
Comfrey’s broad, slightly prickly leaves make it a bit coarse for borders, but there is nothing like a naturalized patch of comfrey to fill in spots that get partial shade. The lush, fountain-shaped plants will form graceful colonies in wildflower meadows, and they are perfect for anchoring the shady edges of a pollinator garden. If you are concerned about invasiveness, grow comfrey next to an area that is regularly mowed, or look for the ‘Bocking 14’ variety, an inter-species cross that does not reseed.
2. Bulk up Compost
One of the best uses for comfrey is as biomass for bulking up compost. The leaves are remarkably rich in potassium, with some nitrogen and phosphorous as well. I use an old knife to gather whole leaves to layer into compost whenever the need arises. Studies of comfrey plantings made especially for biomass production have found that greens can be cut up to four times a year without seriously weakening the plants.
3. Feed the Bees
Comfrey is a favorite forage plant for bumblebees, which may cut slits in the flowers that make the nectar accessible to other insects. On warm summer mornings I often see several bee species feeding on comfrey flowers, as well as the occasional butterfly. If I cut back old flower spikes, the plants rebloom for most of the summer.
4. Use Comfrey as Mulch
A common permaculture practice is to grow comfrey near young fruit trees so the leaves can conveniently be cut and spread as a surface mulch under the trees’ drip lines. I also like to chop comfrey leaves into pieces and use the greens as a surface mulch, which is then topped by a second layer of straw, hay or grass clippings. In this way, the nutrients in the comfrey leaves enrich the soil from the top down as they decompose.
5. Ferment Comfrey into Fertilizer
Fermenting comfrey leaves into a fertilizer, called com-fert, is an old English tradition best carried on outdoors during the warmer summer months. As explained in Grow Your Own Fertilizer Using Comfrey, you chop a bunch of leaves into a bucket, weight them with a brick, add a little water, and cover loosely to slow evaporation. You can let nature take its course unattended for a few weeks, or hold your nose and stir it with a stick every few days. When the stench subsides after a month or so, harvest the brown goo at the bottom and store it in an airtight jar. Dilute the concentrate with water at least 1:15 before using it as a foliar feed for garden plants.
6. Make a Comfrey Poultice
Let’s hope you don’t drop something heavy on your toe or sprain your ankle, but if you do you can make a comfrey poultice that speeds healing by promoting circulation. In herbal lore comfrey is known as knitbone or boneset. Practices vary from wrapping whole bruised leaves around the injury to applying warm poultices made from comfrey leaves and/or roots. For my home first-aid kit, I harvest a few robust roots and dry them, then store the dried comfrey roots in a dark, cool cabinet. Just in case.
7. Comfrey Tea for Houseplants
Last year I dried a few bundles of comfrey leaves, crumbled coarse pieces into a jar, and used it all winter to enrich the water I used for my indoor plants. I think they liked it, and the procedure is so simple. Place 2 inches (5 cm) of crumbled dry comfrey leaves in a quart jar, fill with water, shake and let sit overnight. Strain out the leaves and you have a gentle comfrey tea for houseplants.