Comfrey tea is rich in nitrogen and potassium; it is a nutritious side-dressing for fruiting vegetables. Tomatoes, peppers, cucumbers, and berries use nitrogen to support leaf growth and potassium to promote flowers and fruit. The nitrogen-phosphorus-potassium ( NPK ) ratio of dried comfrey leaves is 1.8-0.5-5.3; comfrey also contains calcium.


Comfrey leaves are quick to rot. The water will turn into a dark, foul-smelling manure tea in about 20 days and will brew darker and darker if left for as long as 6 weeks. The lid will keep flies out.

  • Draw the tea from the container and dilute it by at least 50 percent; some gardeners dilute comfrey tea by 10 times before side-dressing plants. If you put a tap at the bottom of the container, you can add leaves and water to the top to keep new tea brewing for months.
  • Apply comfrey tea as a side-dressing or foliar spray; comfrey tea is potent so let a little go a long way. Use comfrey tea as a side dressing every 10 to 14 days from flower set through the development of fruits. As a foliar spray, quit applying comfrey tea at least a month before harvest. Comfrey tea diluted is an excellent fertilizer for container vegetables. (Comfrey tea as a foliar spray has been found to slow the growth of powdery mildew spores on plant leaves.)



Wilted comfrey leaves can be used as sheet-mulch manure. Place two or three layers around the base of plants or bury them in the soil 2 inches deep to the side of crops including tomatoes, peppers, potatoes, currants, gooseberries, and fruit trees. The high nitrogen and potassium content of comfrey leaves will be almost immediately available to crops. (High nitrogen fertilizers are not a good match for leafy crops such as lettuce and spinach; the nitrogen boost may cause them to go to seed prematurely. As well, high potassium fertilizers are not a good match for rooting crops such as carrots.)


To make a comfrey fertilizer concentrate, pack comfrey leaves tightly into a container, weigh them down, cover, and let them rot. In about 3 weeks, you will have a liquid fertilizer concentrate that can be mixed with 15 parts water to 1 part comfrey goo and used as a fertilizer side dressing.


Comfrey leaves can also be used as a compost activator in compost piles rich in brown carbon material. Place a layer or two of comfrey leaves on the top of the compost pile and sprinkle garden soil on top. The quick rotting comfrey leaves rich in nitrogen will work with bacteria and soil organisms to speed the composting of dried leaves and other high carbon materials.


Uses of comfrey in the Garden

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.


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 by 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 free of pest and disease.


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.


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.


Comfrey as a fertilizer

One Reply to “Comfrey as a fertilizer”

  1. Hello, Thankyou for the information here. I was looking for ideas about dehydrating comfrey and powderizing it to add as a potassium source in the gardens. Do you have any idea how much to use? For example…My 15 gallon potatoe pots are about 1.3 square feet each. Just dont want to over-do it or under-do it. Thankyou so much for any info you could offer, also, do you reapply during the season or just once in spring.

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