Comfrey fell out of favor along with backyard gardens after WWII, and my mother’s generation lost the knowledge of why so many backyard gardeners grew comfrey for anything other than medicinal uses. Even growing comfrey for home herbal preparations fell out of favor with the rapid increase in pharamaceutical preparations at the corner drug store.
So why should a gardener grow comfrey? Free fertilizer, for one thing!! This is because comfrey roots dig deep, deep down in the soil and bring up many needed nutrients other plant roots cannot reach. These nutrients are stored in the fast-growing comfrey leaves, and are extremely valuable for any gardener for plant nutrition and herbal preparations.
One nutrient found in quantity in comfrey is potassium, which is an essential nutrient needed by all plants to make their fruit or flowers. In fact, comfrey leaves have over twice the potassium of cow/horse manure! Some potassium-hungry plants are root crops like potatoes and beets, heavy production plants like tomatoes and grains, and fruit bushes. Roses are also a heavy potassium user. Potassium makes it possible for the plant to use nitrogen, and to increase the protein production.
The comfrey I grow traces to the Quaker comfrey (also called Russian, or blue comfrey) [S. asperum Lepechin (S. asperrimum Donn)], a natural hybrid of S. officinale L. and S. asperum Lepechin, introduced into Canada in 1954. The majority of comfrey grown in the United States can be traced to this introduction.
I put a layer of comfrey leaves in the trench when planting potatoes. Let the leaves wilt a day or two, put them in the trench, and cover with soil. Then add the seed potatoes as normal. I also make a thick mulch of chopped comfrey leaves to place around my tomato and pepper plants after they have set fruit, where it breaks down slowly to release nutrients.
One cautionary note: do not use the raw comfrey flowering stalks or root parts as mulch or in a trench… they will root, and comfrey roots grow deep. Any tiny piece of root left in the ground will make another comfrey plant!
I don’t have the time (or the inclination) to make comfrey compounds like a gardener’s hand cream or an all-purpose cream for healing scrapes, bruises, and bug bites, but comfrey is great for all of those. Here’s an article by Bev Walker about how to do it. I have written a more detailed look at potassium here, as part of my series on plant nutrition. (See sidebar for published articles.) Here’s a link for making liquid comfrey fertilizers and tea.
Grow some comfrey… it’s very useful, and has pretty flowers to boot!