Comfrey (Symphytum officinale) is a perennial flowering plant in the borage family (Boraginaceae), historically known as 'knit bone' due to its use as a medicinal poultice.
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This perennial plant is found naturally in moist grasslands in western Asia, Europe and North America, and is a hardy plant that can grow to a height of one metre, it has a parsnip-type tap root that can extend a number of metres below the plant and beautiful bell shaped flowers that are very rich in nectar.
These characteristics mean that the plant's roots are able to access minerals deep down in the soil - minerals that would be inaccessible to most other plants with shallower root systems. As the plant takes up the minerals from the soil they become part of the above-ground plant, which can then be used as a precious feed in your garden, either by adding it to your compost pile or by making a liquid feed. A comfrey feed is high in phosphorous, an essential mineral for plants when setting flower or growing the subsequent fruit.
The deep root system of the comfrey plant mean some careful consideration is needed before planting it, as it's unlikely you will ever get rid of it should you decide it's in the wrong place! In fact, the common version that you find is incredibly invasive. As such, most gardeners use a variety cultivated in 1950 known as Russian Comfrey or Bocking 14. The benefit of this variety is that it produces non-viable seeds, so cannot spread like common comfrey.
Comfrey flowers are incredibly attractive to bees: we often find ours covered in solitary bees like the humble bumble and moss carder - in fact, we don't see such a high concentration of solitary bees anywhere else in our garden.
The plant grows so quickly that you can cut it to the ground two or three time per year, however we choose to let the bees have their fun and only cut it back once it starts to go over in early summer.
There are two common methods (outside of composting) of using comfrey to fertilize your garden. The first is to make a comfrey 'tea' by steeping the plant in water, resulting in a liquid that you can take and pour directly onto the garden. The alternative is to make a concentrated liquid in a shorter amount of time - but that does need diluting before being applied.
The downside of the former is that the liquid smells quite badly (no problem if you have somewhere out of the way to keep it while it steeps, but potentially unpleasant if you are short on space).
Partly for that reason and partly because I wanted to use items we had lying around, we chose the second method.
Searching the internet you'll find a myriad of slight variations on this method but the basic principle is basically the same: you put the leaves of the plant into a container with drainage holes in the bottom and add some weight which slowly squashes the leaves and releases the liquid into another container placed underneath the first.
So, for our setup we used a spouted bucket, in which we put a sealed plastic container filled with gravel to give it stability.
Into the bucket we sat a small lidded bin, in the base of which we drilled holes for the liquid to escape into the bucket below.
After stacking them, we add comfrey leaves (the rest of the plant is composted) into the bucket above, then add a weight, such as a stone. replace the lid on the bucket, and then simply wait.
After a 2-3 weeks the process will be complete - we throw what's left of the leaves into the compost and pour out the liquid feed for use when our plants want it.
The feed made in this way needs to be diluted 10 parts water to one part feed. We put the feed directly into a marked container so we can easily gauge how much water needs adding before using it.
Should any garden be without comfrey? I doubt the bees would think so!