Comfrey is a powerhouse in the garden–attracting pollinators and beneficial insects, providing medicinal value, and enriching soil with nutrients. Here are seven ways comfrey can fertilize the soil for healthier and more abundant crops.
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Comfrey: The Permaculture Star
If permaculture had a poster child, it would be comfrey. Comfrey is a multi-functional, prolific, and low-maintenance herb–all the things we look for when selecting plants for the permaculture garden. Comfrey flowers attract pollinators and the large leaves provide habitat for beneficial insects. It is also one of the most potent and effective medicinal herbs known.
Harvesting nutrients from deep in the soil with its long roots, comfrey is high in nitrogen, phosphorus, potassium, potash, and calcium.
Here are seven ways we can take advantage of comfrey’s goodness to enrich and condition the soil for healthier and more bountiful crops (for free!).
1: Activate Compost
Comfrey cuttings are high in nitrogen, making them an excellent bioactivator in the compost bin. If you have a large amount of dried brown material–such as fall leaves–layering it with comfrey cuttings is an efficient way to balance out the carbon-to-nitrogen ratio and jumpstart decomposition.
To give the compost pile an immediate kick into high gear, collect comfrey leaves and crush them. We use garden scissors to quickly cut through the leaves roughly. Add a small amount of water and stir/crush for a minute or two to make a paste. Add more water to liquefy, then pour the entire solution onto the compost pile. This quick little extra step is the equivalent of chewing food. The pre-digestion helps beneficial micro-organisms of the compost pile (like those of our stomachs) get to work faster.
The finished compost will have a higher nutrient content with the addition of comfrey cuttings.
2: Comfrey Manure
Green manure is an alternative to–or supplement to–animal manures as a soil amendment. Green manure plants are simply cut back and turned into the soil. For those on city lots who may not have easy access to livestock manures, green manures are the way to go.
Manure sources are rated for their N-P-K values (nitrogen-phosphorus-potassium) since they are the primary nutrients plants need for healthy growth.
When comparing comfrey manure (1.8-0.5-5.3) to chicken manure (1.1-0.8-0.5) for example, we can see that they are relatively close in value, with comfrey actually having higher nitrogen and potassium values. By comparison, the value of homemade compost usually falls around 0.5-0.5-0.5, highlighting the fact that the benefit of compost is in its beneficial microbial content and as a soil conditioner, rather than as fertilizer.
When using comfrey as a green manure, add chopped comfrey to garden soil in the fall. Gently mix it into the top layers of the soil using a digging fork. By spring, it will have mostly decomposed and enriched the soil.
Alternatively, comfrey manure can be added in the early spring–at least two weeks before planting. To jumpstart the decomposition of the comfrey manure at this late date, try the quick method explained above under Activate Compost.
Note: Comfrey may not emerge from its winter slumber until late March/early April depending on your location, so there may not be comfrey leaves to chop and spread before the growing season gets underway.
To counteract this potential problem, see the next step!
3: Powdered Comfrey
Having dried comfrey on hand is a habit that I have grown accustomed to. I use the dried comfrey leaves to make a healing salve for cuts, scrapes, bites, bruises, sore joints, and all manner of external ailments.
Dried and powdered (root or leaf) comfrey can also be used to build and fertilize garden soil. Make your own by air drying comfrey or using a dehydrator at 95 degrees until crisp. Remove the dried leaves from the stems and use a blender or coffee grinder to make a powder. Store in an air-tight container.
Simply mix powdered comfrey into the soil with a digging fork, about two weeks before planting. Remember that powdered comfrey is more concentrated than fresh leaves, so a little goes a long way. A sprinkle along each row should be plenty. The benefit of using the powdered comfrey is that it can be used in the late winter/early spring garden before the comfrey plants have woken up and produced leaves. The powder will also decompose more readily than fresh leaves, which is better for the spring garden.
4: Condition Soil
Comfrey’s roots reach 6-10 feet deep into the earth, breaking up heavy clay and creating channels for aeration and better water absorption. Over time, its decomposing leaves and roots will fertilize the soil. This dual action of decomposing leaves and roots can help improve marginal land. Since comfrey prefers rich soil, when planting it in poor or damaged soil, give it a head start by adding a shovel of manure or compost.
5: Boost Seedlings
Young perennials (fruit trees, berry bushes, asparagus, herbs, etc.) and fruiting vegetable seedlings (tomatoes, peppers, cucumbers, squash, etc.) will enjoy a nutritional jumpstart from comfrey. At the time of planting, bury a few comfrey leaves (not flowering stems) underneath each planting spot. As the comfrey leaves decompose, they will provide essential nutrients and help the young plants grow strong and be pest- and disease-resistant.
6: Liquid Fertilizer
Compost tea is an excellent way to provide an immediate nutrient boost to established plants. It is made by steeping fresh plant matter in water for a certain amount of time, straining the liquid, and using it to water stressed plants for a mid-season boost.
The extra nitrogen in comfrey compost tea will help overall growth, while the potassium will encourage better flowering and more vigorous growth in perennials and mature fruiting vegetable plants such as tomatoes, peppers, potatoes, cucumbers, etc. Comfrey compost tea is not recommended for young plants.
To make a strong comfrey compost tea: Fill any size container halfway with fresh comfrey cuttings. Fill with water, cover, and steep for 3-6 weeks. Warning: This will smell really bad! Strain off the liquid and dilute by half. Or if using a hose end sprayer, no need to pre-dilute.
To make a weaker (less smelly) comfrey compost tea: Add one gallon of water for every quart of fresh comfrey cuttings. Let sit for three days, stirring daily, then strain and use full strength.
For a quicker comfrey compost tea: Measure one quart of water for every ounce of dried comfrey. Boil the water and pour over the dried comfrey. Let it cool for 5 minutes, then cover and steep for 4 hours. Strain, then dilute with 1 gallon of water unless using the hose end sprayer.
Be sure to compost the leftover plant solids.
7: Comfrey Mulch
Mulching—in general—is a great way to protect soil and prevent erosion. Mulching with comfrey—also called chop-and-drop—will help to retain moisture and protect beneficial soil organisms. Comfrey mulch is a slow-release fertilizer that is best used under perennials and fruiting vegetables.
We grow comfrey underneath our cherry trees so that the fruit trees benefit from comfrey fertilizer. Read more about growing comfrey under fruit trees in my post The Cherry Tree Guild.
For more information about growing comfrey and using it as a mulch, see my post What is Comfrey and How to Grow It.
Here’s the kind of comfrey that I buy for planting.
As you can see, growing comfrey provides a lot of value to the gardener—reducing costs on imported fertilizers, creating healthier plants, and improving yields.
How have you used comfrey in your garden?