To loosen your clay soil, grow the comfrey plant. Better yet, it'll entice bees and other pollinators to your yard. Used as a mulch, fertilizer, compost accelerator, pollinator attractor, and clay soil breaker, the comfrey plant is an invaluable addition to a garden. As long as you don’t live in the plant’s invasive range, you can gain a lot of benefit from planting it.
The first comfrey shoots appear in spring. By June it has grown waist high with a multitude of pretty bell-shaped, pink to purple flowers, each one with a tiny bee’s bottom protruding from the end as they feast on the rich comfrey nectar. I let the bees feast for a few weeks before taking my first harvest, cutting the stalks at ground level and then roughly chopping to add a much-needed nitrogen boost to my cold, carbon-rich sleepy compost.
Within a few weeks, new leaves have sprouted 12-15 inches long and are ready for harvesting to feed the now-hungry vegetable and fruit crops. Comfrey foliage is rich in potassium and trace minerals, magnesium, and calcium, perfect for tomatoes, peppers, and pumpkins. And so, the cycle begins for at least another two harvests. That’s at least three to four harvests per season. What’s not to love about comfrey? Comfrey is a hardy herbaceous perennial and a member of the borage family, Boraginaceae, which includes borage, forget-me-nots, echium, brunnera, and cerinthe.
There are two main species of comfrey, Symphytum officinale, also known as common comfrey native to Europe and Asia, and Russian comfrey (Symphytum x uplandicum), a naturally occurring hybrid first discovered in Upland, Sweden in the 1800s. It has naturalized in parts of Canada. S. x uplandicum is a cross between common comfrey and Symphytum asperum, the blue-flowered rough or prickly comfrey originating in Russia.
Common comfrey has been cultivated since ancient Greek and Roman times when it had medicinal use primarily as a poultice to heal broken bones, bruises, and other injuries, hence the common names knitbone, knitback, and bruisewort. Although similar in appearance and cultivation, there are some key differences between common and Russian comfrey. Common comfrey can reproduce via seed dispersal, making it invasive in certain parts of the world. Russian comfrey flowers are sterile, therefore propagation is through cuttings and division. Russian comfrey leaves are larger, producing higher yields.
The first green shoots of comfrey emerge from your garden bed as basal growth from its crown in mid-spring. It quickly forms a large clump with leaves 12 to 15 inches long, lance-shaped, green, and roughly textured with lots of tiny prickly hairs that can be a skin irritant.
As late spring ebbs away and the temperatures rise towards summer, thick branching flowering stalks push up from the crown with smaller leaves. Clusters of drooping tubular bell-shaped flowers appear, ranging in color from yellow, pink, purple, and blue, depending on the species. At full height, comfrey can reach three to four feet.
Comfrey dies back naturally after flowering. The heavy stalks often collapse and are quickly replaced by new shoots. Cutting back the plant before it goes to flower will speed up the process of regrowth. Cold autumn temperatures initiate winter dormancy.