Comfrey, until fairly recently, was used for centuries as a medicinal herb. Some of the common folk names for it, such as “healing herb” and “bruisewort,” reflect the healing properties that people once thought it had.
Nowadays we are told that any internal healing properties it might have are largely offset by the danger of it causing serious liver damage. Applying comfrey to the skin however is perfectly safe.
Comfrey, Symphytum officinale, is still a valuable addition to the garden though. The leaves contain a significant amount of all three major plant nutrients: nitrogen, phosphorus, and potassium.
Its leaves contain a higher protein percentage than any other plant, up to 26 percent. Alfalfa, for example, grown by farmers for livestock feed, is considered a high protein source coming in at 18 percent. The higher the protein content a plant has, the more nitrogen it contains.
Comfrey plants have long and vigorous tap roots extending down into the soil 10 feet or more. Their long roots enable the plants to extract both primary nutrients as well as trace minerals from deep subsoil layers unreachable by most other garden plants.
Another interesting trait of comfrey is that in addition to producing vitamin C and all of the other plant based vitamins, it is the only land-based plant that produces vitamin B-12.
All of these nutrients present in the leaves makes them a perfect ingredient for home made fertilizer.
The traditional fertilizer recipe calls for anaerobically fermenting the leaves. Place about a quart of leaves into a 5 gallon bucket along with about 4 gallons of water. Then just let it steep inside the bucket for a month or so.
Because of the high protein content, the fermenting concoction will begin to give off a very strong odor, much like a rotting animal carcass. So make sure you cover your brew with a lid to reduce the smell. The lid will also prevent mosquitoes from breeding in the stagnant water.
If you are in a hurry to use your fertilizer, you can start to use it after 10 days but it will not have as much oomph as the finished product.
A chemical analysis of liquid comfrey fertilizer showed that it contained similar amounts of nutrients to those found in the popular blue soluble fertilizers. In addition, liquid comfrey has other growth promoting factors produced by bacteria that are not present in commercial fertilizers.
The fermented fertilizer works especially well for tomatoes and potatoes.
For a very quick and not so offensive fertilizer, you can make up small batches of fresh comfrey fertilizer in your kitchen. Pick four or five fresh comfrey leaves and place them in a blender. Fill the blender jar with water hot enough to wilt the leaves. Thoroughly blend the mixture and let cool. Strain the leaves from the liquid.
The buzzed up leaves can then be placed around the base of plants as a side-dressing. The liquid is also used as a fertilizer drench when poured into the soil near plants.
The easiest way of all to use comfrey is to spread cut leaves on the soil alongside growing plants. Nutrients will be slowly released as the leaves decompose.
Adding comfrey leaves to your compost will add to the nutrient content as well as giving a boost to the composting process.
Comfrey is a perennial plant that will grow back year after year. While it is usually not very invasive, it is hard to get rid of if you decide to move it from its original place. Even the smallest pieces of root left in the soil will sprout into new plants. So plan carefully before you plant a comfrey bed.
Once your comfrey becomes established, you'll have a lifetime source of natural fertilizer.
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