Commonly comfrey is cultivated for two uses and promoted by growing methods like Permaculture. Comfrey is often used in organic gardening as a fertilizer and mineral accumulator.
Lab Results:
http://www.albertaurbangarden.ca/wp-content/uploads/2015/02/150214_AlbertaUrbanGardenCertificateofAnalysis-RevisedReport.pdf
Comfrey is a common perennial herb native to Europe that grows in damp areas such as river banks.
I was first introduced to comfrey when a viewer gave me a plant. Comfrey is simple to propagate by placing the tuber in the soil and cover, shortly after a leafy plant will emerge. Be careful when planting comfrey or disposing of any extra tubers as they will often re-root and can take over unintended areas and can be hard to get rid of. It is also a good idea to cut and completely remove any of the flowers and their stalks in order to prevent spreading. There is a sterile variety called Bocking 14 Russian Comfrey that you don’t have to worry about the flowers.
I planted mine soon after receiving it. I chose to place it in the area I use for making leaf mold. This location is convenient as the pile breaks down it releases nutrients like nitrogen into the surrounding area feeding the plant. The location is out of the way and will not shade any of my food crops.
In order to understand better what kind of benefits comfrey has as an organic fertilizer and mineral accumulator I decided to send samples into Maxxam Analytics.
I started by drying some of the last comfrey leaves in the fall. I then had the sample tested for immediately available NPK and trace elements.
The total immediately available NPK of comfrey is 0.35 – 0.73 – 7.35
These results represent the NPK that is immediately available to plants in the garden soil. This analysis does not account for the nutrients that are tied up in larger more complex molecules. As the comfrey is broken down these nutrients are released into the soils nutrient cycle.
The University of Minnesota* [2] assessed the total elemental nitrogen in comfrey samples. Their results ranged from 3.36 % to 3.70%. Our lab results found total phosphorus and potassium of 5300 and 70,000 mg/kg and when converted to % molecular weight the total NPK of comfrey is:
3.7* – 1.21 – 8.43
Comfrey turns out to have a great NPK both immediately available and long term. The second test we had run was the total trace elements. These results will let us know if using comfrey is a good way to add trace elements to our gardens soils.
Plants require a variety of elements in the soil in order to complete their life cycle and produce crops. These elements are broken into two categories essential and beneficial. It is rare for garden soils to lack any of these beneficial and essential elements however lower levels can impede the nutrient cycle.
Comfrey contains Boron, significant volumes of Calcium*, Iron, Magnesium, Sodium, and Sulphur. Additional elements were reported however due to the low levels and the detection limit error rate the reported numbers are not as reliable however they are still present. These include Manganese, Molynbdenum, Nickel and Zinc. Other literature sources also found Cobalt and Copper.
Once the nitrogen phosphorus and potassium have been added to the total these results represent 15 of the 18 essential and beneficial elements that plants take up from the soil. Missing from the analysis is Silicon, selenium, chlorine.
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