As I continue my journey deeper into veganic gardening I am perpetually amazed at the wealth of resources present in our own backyard. It seems that anyone with a proper compost pile, a source of mulch or green manure and common beneficial “weeds” scattered about has all the resources needed to help their garden thrive.
One of my new favorite herbs for the garden or “weeds”, depending on your perspective, is comfrey (Symphytum officinale), which has a wealth of uses for both our own health and the health of the garden.
NPK ratio of Comfrey
Uses for Comfrey in the Garden
Mulch or Side Dressing
Health Benefits of Comfrey
Comfrey’s deep roots work to bring nutrients up from the subsoil. These nutrients are then made available in the abundant number of leaves it produces every year (4-5 lbs of leaves per established plant/ per year). The leaves are rich in nitrogen and potassium with a decent amount of phosphorus as well, making them a wonderful homegrown fertilizer. Researchers in British Columbia analyzed the NPK (nitrogen-phosphorus-potassium) ratio of comfrey* and discovered that the leaves have a remarkable NPK ratio of 1.80-0.50-5.30. When we compare these nutrient ratios to that of animal manure we can see how far superior comfrey is.
Dairy Cow: .25-.15-.25
Note: Naturally, nutrient values of animal or plant based manure can vary greatly from specimen to specimen.
* Air-dried powdered comfrey leaf tissues.
As you can see from this list, the nitrogen content of comfrey is higher than almost all animal manures found on the market today and its potassium concentration is far superior to all, making it an ideal fertilizer for plants that produce flowers, seeds and fruit for which potassium is an essential component. This along with the more important ethical and environmental incentives for not using animal inputs in our gardens makes growing comfrey as a fertilizer a win-win.
If you don’t think the NPK ratio of the dried leaves is impressive enough, you can also make a concentrated liquid fertilizer out of comfrey (see directions below) with an NPK ratio of about 8-2.60-20.50! (Although you’ll want to dilute this before use.) The leaves are also full of silica, calcium, iron, magnesium and other essential nutrients to help your fruiting plants thrive.
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.
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 place 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 courser. 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 slowly and steadily fertilize your plants you can use comfrey as a mulch. Because comfrey is high in nitrogen it won’t steal nitrogen from the soil as 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.
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 voila – 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. Bronners) 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.
After hearing all the benefits of using comfrey in your garden (more on the health benefits to come) 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 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 flowing 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.
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 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.
Health Benefits of Comfrey:
Comfrey is also called knitbone, knitback, consound, blackwort, Ass Ear, Slippery Root, boneset, yalluc (Saxon), gum plant, consolida and bruisewort.
From the pattern of these names you’ve probably guessed that comfrey can do more than benefit your garden. It also has powerful healing properties, supporting the body’s ability to repair damaged tissue and bones.
Comfrey roots and leaves contain a substance called allantoin, which along with other beneficial compounds in the plant, supports healthy cell growth and reduces inflammation. Comfrey has been used externally as a poultice or ointment to heal bruises, broken bones, closed wounds, pulled muscles and ligaments, fractures, as well as reducing inflammation from sprains and more.
There is some controversy over comfrey though because it also contains poisonous substances called pyrrolizidine alkaloids that have been shown to be toxic to the liver when ingested. For this reason, oral comfrey products have been banned in many countries including the U.S. It is reported that some of the pyrrolizidine alkaloids can be absorbed through the skin as well, but there are varying opinions as to the actual risk of poisoning through topical use. It is best to find a knowledgeable herbalist or naturopath who can teach you the correct way to use this wonderful herb. Most recommend using Comfrey externally for no more than 10 days at a time and no more than 4-6 weeks out of the year. While many feel that caution with this herb is important it is also a powerful healing tool if used correctly.
So now that you know all about this wonderful herb, weed and garden companion, get out there and get growing!