We love mulch, and when we install a food forest, we will bring in plenty of wood chips. However, once the planting is established, growing mulch under the tree eliminates trudging around with a compost-filled wheelbarrow, because the guild will build its own soil. Mulch makers include soft-leaved plants such as comfrey, artichokes, cardoon, rhubarb, clovers, and nasturtiums, all of which can be slashed and left to compost in place.
The plant most commonly referred to and used in gardens is Russian comfrey, a naturally occurring hybrid of two wild species: common comfrey, Symphytum officinale, and prickly comfrey, Symphytum asperum. The seeds of Russian comfrey are sterile, so this variety is not going to take over your garden.
Comfrey produces large amounts of foliage from late May (late spring) until hard frosts in October or November (late autumn). The plant is excellent for producing mulch and can be cut from 2-5 times per year depending on how well the plants are watered and fed. The plant grows rapidly after each harvest.
A ring of comfrey around the tree can be hacked down four or five times in a summer. It feeds the soil minerals and organic matte and the resulting compost is home to a population of worms, fungi, and bacteria that will suppress disease.
Comfrey has roots of up to 6 1/2 feet deep that use nutrients in the subsoil that would otherwise wash away with the underground soil water or remain inaccessible to other plants. The nutrients, once taken up from the roots, are relocated throughout the plant where needed with some of them ending up in the comfrey leaf mass. When cutting the leaf mass and applying to the soil surface, the mined nutrients are returned and again made accessible to shallower rooted crop plants.
Comfrey leaves contain a great balance of major plant nutrients (N,P,K) and can be fed to plants as powder, direct mulch or by steeping chopped comfrey leaves in water for several weeks to produce a thick, dark liquid that can be diluted with water and applied to plant roots.
Learn to love these soft-leaved plants that can add so much to the understory of your food forest. And if you see a similarity between this comfrey plant and the beautiful borage with a bee in our last blog post, it is because they are from the same family. Borage and comfrey are two different species, but they are members of the same plant family and look very similar when not in bloom. Whereas comfrey is a perennial plant (comes back every year), borage (Borago officinalis)is an annual that happily re-seeds.