Comfrey has many wonderful uses for healing and in the garden. In this post you’ll find five different ways to use comfrey as a fertilizer. I’ve also included some easy growing and harvesting instructions to make sure you don’t end up in a prickly situation.
Comfrey is a hardy herb (or weed, depending on your perspective) and it isn’t easy to get rid of once it’s planted, so knowing where and how to plant and harvest comfrey is important. Once you hear about all its wonderful uses in the garden and its NPK ratio, though, you’ll probably seek out the perfect spot to forage for it or plant it around your yard.
How to use comfrey in your garden:
Compost activator: Comfrey is an excellent addition to any compost. It will not only enrich your compost but will also encourage the pile to heat up, speeding up the composting process. This is particularly important if you have lots of carbon-rich material in your compost (dry brown material like twigs, straw, dry grass, etc.) Simply place alternating layers of fresh comfrey leaves and other nitrogen-rich material (fruit and veggie peels, etc.) with carbon-rich material (twigs, dry grass and hay etc.) to make a rocking compost pile. Don’t overdo the comfrey though, or it will break down quickly into a dark gooey liquid and can heat your compost pile too quickly or add too much moisture to the mix.
Next: Liquid fertilizer and more!
Liquid fertilizer: Comfrey makes a powerful liquid fertilizer. The most common methods involve stacking dry leaves under a weight in a bucket and filling the bucket with water, and then allowing them to decompose for 3-5 weeks, making a “comfrey tea.” The second method also involves stacking the dry leaves in a bucket with a weight on top, but first you cut holes in the base of the bucket and then stack that bucket inside another bucket that it can drip into. When the dry leaves (no water added) begin to decompose, a thick black comfrey concentrate will drip through the hole and into the second bucket. This must be diluted at approximately 15:1 before use. Both mixtures are rather smelly and powerful, so make sure you have a tight lid on top of your fertilizer buckets and dilute as needed.
An important note about comfrey as a fertilizer: While nitrogen encourages leaf growth, excess potassium can slightly stunt growth and make leaves coarser. At the same time, potassium also promotes developing flowers and fruit. Thus, it is best to apply comfrey fertilizer after the first flowers have set, to let the leaves develop as needed and then support the fruit/seeds/flower growth.
Mulch or side dressing: If you want to fertilize your plants slowly and steadily, you can use comfrey as a mulch. Because comfrey is high in nitrogen, it won’t steal nitrogen from the soil, and it breaks down like woodchips, straw, leaves and other carbon-rich material does. Simply take some of the fresh cut leaves and sprinkle them around your plants (some people like to let them wilt a bit in the sun before adding them to the bed to make sure they don’t sprout). This is best as a mulch for flowers, fruiting vegetables, berries and fruit trees. Leafy greens and root crops like carrots and beets will do better with another type of mulch, because the nutrients in comfrey can cause these plants to go to seed/flower early. Experiment with small amounts of comfrey to see how your plants respond.
Next: Potting mixtures and soil amendment
Potting mixtures: I haven’t done this myself, but there are enough seasoned gardeners out there touting its benefits to mention it here. I’ve heard tell of recipes that use both peat and well-rotted leaf mold mixed with chopped comfrey leaves. Both mixes are left to decompose over a number of months and then voilà – a beautiful nutrient-rich potting mix!
Soil amendment: To give your transplants an extra boost, use freshly cut comfrey leaves (do not use flowering stems in case they take root) as fertilizer in your planting holes. Because the leaves break down quickly, the plants will be given an extra nutrient boost right at the roots. It is a good idea to put the leaves in the sun 1-2 hours to wilt them and prevent them from taking root. After they are wilted simply place the torn up leaves at the bottom of the planting hole, add some dirt on top to protect the roots of your new transplant from being burned as the nutrient-rich comfrey leaves decompose, and fertilize the soil!
Disease control: “Scientists at Moscow State University in Russia observed that powdery mildew spores that landed on wheat seedlings sprayed with comfrey tea did not germinate, and the wheat seedlings did not become infected. The researchers concluded that the comfrey tea sprays had activated natural defense mechanisms in the wheat seedlings, making them more resistant to disease.” —Earth Seed
To help prevent disease and fertilize your plants, diluted and strained comfrey tea or comfrey extract can be made into a foliage spray by adding a few drops of a gentle liquid soap (such as Dr. Bronner’s) to the mix, which helps the spray stick to leaves. You can use a watering can with a gentle pour, but a garden sprayer will work better. Before you add your diluted liquid comfrey fertilizer to the can or sprayer, strain the liquid through muslin or another fine filter, or you’re likely to clog the nozzle rather quickly. Make sure to spray both the underside and the top of the leaves.
Next: Growing Comfrey
After hearing all the benefits of using comfrey in your garden, you’re probably interested in finding some to plant around your yard, which I highly recommend! Before you do, though, here are some important things to know.
1. Part of the reason comfrey is so wonderful is because it is a hardy plant with deep roots. But because of this fact, it is important make sure you know what you’re doing when you select the site for your comfrey patch. Comfrey is a perennial, and if you decide you want to get rid of your comfrey patch (I have no idea why you would though), you’re going to have a hard time! A new plant can sprout from even a small section of root left behind, and while it does not have trailing roots, comfrey’s main taproot can go down many, many feet into the ground.
2. The leaves are hairy and can be irritating to the skin, so avoid planting comfrey somewhere you’re bound to brush up against it regularly.
Comfrey is able to grow well in most soil conditions, except for shallow or dry chalky soil. It will not spread unless the roots are severed or if you let it go to seed. You can easily prevent comfrey from spreading by not cultivating the soil around the comfrey and either cutting off the flowering stalks as soon as they appear or by planting a sterile version of comfrey. It can be grown in full sun or partial shade, but does enjoy moist, fertile soil.
Next: Harvesting Comfrey
Growing comfrey near a compost pile or on the site of an old compost pile is a great way to utilize any nutrients that might have leached into the soil as the compost weathered. Although comfrey will grow well on its own, it does source nitrogen and other nutrients from the soil and will enjoy being fertilized with compost and other organic matter at least once a year.
It can easily be propagated from root cuttings or seed, but be conscious of which variety you are planting (there are some sterile varieties, and poisonous foxglove is sometimes mistaken for comfrey).
Comfrey is easy to harvest. Once it is established (after the first year), you’re likely to get four or more harvests a year amounting to 4-5 pounds of leaves PER plant! Allow your comfrey to establish itself over the first year by harvesting individual leaves here and there, but not over-picking it. After the first year, as stalks start to form for flowers or when the plant is about two feet tall, you can harvest the plant. Simply cut off all the leaves/stems about 2-3 inches above the ground. Many people find the hairy leaves irritating to their skin, though, so wearing gloves and long sleeves as you harvest is a good idea. After harvesting, give your comfrey a good watering, fertilize if so desired, and renew the mulch layer if you had one. If you discover that you don’t have enough comfrey plants for your needs, simply take a spade and slice into the middle of the plant, dividing the head and roots into two or more pieces, and replant the severed sections.
As you can see, comfrey is easy to grow and use in your garden. For more on the health benefits, read “The Wonder of Comfrey.”