Comfrey (Symphytum officinale)has long been used in the garden mainly for it's use as an organic fertiliser. The properties of this "wonder plant" are well known to the older generation of gardeners and growers as well as those interested in organic growing. However it's popularity has decreased over the years with main stream gardening as synthetic oil based fertilisers became the norm and were relatively cheap to produce and easy to apply. With the ever increasing price of oil, it's finite availability and the harm it is doing to both the local and world environment it must be about time that comfrey is rediscovered by the gardening community as a valuable source of nutrients and food for pollinators.
It has long been the case that buying synthetic fertiliser was the least labour intensive and cheapest way to provide nutrients in the growing environment. I feel the tide is changing though and more people should be investing the time needed to produce their own fertiliser which is both cost effective and kind to the environment. Yes there is work involved with making fertiliser from comfrey but this can be offset against the high and forever increasing costs of the synthetic alternative, even when you attach a cost to your time.
Of course you will need room for the plants to grow in your garden but they are extremely adaptable and will grow well in conditions which are far from favorable to the majority of other garden plants. They enjoy damp, fertile locations and will effectively "mine" lost nutrients which have been leached deep into the soil around compost and manure heaps. This is because of their deep rooting systems which can go down several feet. It is advisable however to grow the bocking 14 variety which does not self seed unless you want the plant popping up in unwanted places. Also the plants can be rather hard to get rid of once established as the roots go so deep and even the smallest piece left in the soil can regrow. For this reason it is best to think with a long term view when deciding where to plant.
Once the plants have established for at least a year and are growing strongly you can start to harvest the leaves. This should be done before flowering occurs and upto three cuts can be achieved in a year. Harvesting after september is not advised however as the plant needs a chance to recover before it goes in to it's winter dormancy. It is good practice to try and replace nutrients which are extracted through the constant harvesting as over time the plants will decrease in vigour. You may be thinking what is the point of using valuable fertiliser in order to make another form of fertiliser ? Well the answer to this is that comfrey is an almost indestructible plant which will tolerate certain forms of fertilisation that other plants just could not cope with for example fresh urine and manure, copious amounts of wood ash (good for people who have woodburners) and any home made compost that you would not want to use anywhere else.
Harvest the plants using a method you feel to be the most appropriate according to the time and tools that are available and the amount of plants to be cut. Put these cuttings in a suitable container which is large enough and preferably has a tap or similar device at the bottom, out of which the resultant black liquid can flow into a storage vessel. The process will take a week or two and you should leave it until no more liquid is coming out. Empty the residue on to your compost heap and decide how and where you are going to use the nutrient rich black liquid which has been collected.
It is not a good idea to use this concentrated liquid fertiliser neat as it will damage the plants it is applied to. Dilute at one part concentrate to between ten and twenty parts rain water. If applying to ornamental plants, shrubs and trees this can be done as a soil drench using a watering can with the rose taken off. Not many people do this but comfrey fertiliser can be used to feed your lawn. On a small lawn this can be done effectively using a watering can with rose but on large areas you are going to require a knapsack sprayer. The important thing to remember when doing this is that the diluted solution must be strained first in order that the watering can rose or sprayer filters do not become blocked. Plants can use the fertiliser as a fast acting foliar feed but i much prefer to apply as much water as possible during the process so the soil is drenched also.
There are other uses for comfrey apart from making liquid fertiliser such as adding it to the compost heap as an accelerator, mixing with leaves to make enriched leaf mould or burying in trenches beneath food crops and new plantings. Leave one or two plants to flower every year if you have enough of them and you will soon have bees and other pollinators flocking to your garden.
It is about time that Comfrey made a large scale return to mainstream gardening instead of being a secret of organic gardeners and allotment holders. Do your bit and help raise awareness of this forgotten "wonder plant". At Eco Garden Maintenance we make a point of promoting it's use to all our customers even if it is only as an addition to the perennial border or around compost heaps to soak up the lost nutrients leached deep in the soil.