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Comfrey Tea Fertiliser

Comfrey is a fast growing herb that grows in parts of Europe, Asia, and North America. It can grow up to 5 feet tall with long slender leaves, black skinned roots and clusters of purple, blue, and white flowers.

Whilst comfrey is a wonderful plant for gardeners; a word of caution, some comfreys are difficult to control, they spread everywhere and are bets to be avoided. The variety Bocking 14 has been tested and compared with others and found superior in every respect. It can provide a cost effective nutrient rich source of fertiliser that can be used throughout the year. Best of all, Bocking 14 is sterile. It will flower and provide nectar and pollen aplenty but will not produce viable seed and spread. Rotovate it, however, and every little piece will spring into life. Take root cuttings and pot on and you can bulk up your collection. Bocking 14 plants are available from many on line sources.

The growing of comfrey has many advantages for gardeners and whilst it can be used for animal and poultry foodstuffs the best of all is that it can provide a cost effective nutrient rich source of fertiliser that can be used throughout the gardening calendar. The leaves can also be used as a mulch, liquid feed, to boost compost and when used as a foliar spray can prevent powered mildew.

Comfrey, in permaculture terms is called a ‘dynamic accumulator’ providing all three micronutrients essential for the growth; that is nitrogen(N) phosphorous(P) and potassium(K) commonly termed NPK. In addition, it contains high levels of other important nutrients such as magnesium and calcium.

Dynamic Accumulator
Dynamic accumulators is a term used in
the permaculture and organic growing
literature to indicate those deep rooted
plants that gather certain minerals or
nutrients from deep within the soil and
store them in a more biodegradable
form and in high concentration in their
leaves. These can be used as a source of
fertiliser or mulch.

The comfrey tea making process involves the breakdown or decomposition of comfrey leaves, either shredded or whole, in water over a period of time. Eventually the breakdown will result in an extremely smelly greenish brown slurry. Once complete the decomposed leaves which may be place on the compost heap or used as a mulch.

1lb = 454grams 1kg = 2.2lbs
1litre = 1.75 pints 1gallon = 4.55 litres
1litre = 1000 cubic centimeters
1gallon = 4550 cubic centimeters

Ratio of one gallon of water to half a pound
of leaves. e.g. fill a 5 gallon bucket with
water and 2.5lbs of comfrey leaves

The longer the leaves are steeped in water the stronger the resulting tea. Normally, between two and six weeks will provide a good strength of tea which needs to be diluted before use. Depending on the method used for steeping the leaves the resulting tea can be stored in screw-top bottles for use later.

Steeping Methods:
There are several methods of steeping the leaves to obtain the fertiliser the most common is to place the leaves directly into a bucket. The problem with this is that it is a messy job separating the decaying leaves in solution. Placing the leaves in a hessian sack will make this easier. Alternatively; one may use a barrel/container with a tap at the bottom. Using this method and continually adding water and leaves provides a regular supply of fertiliser
The important that the leaves are placed in a hessian sack. A quick steeping method similar to brewing tea is to pour boiling water over the leaves and leave for around 24 hours. Remember, to place a lid on the container whatever method is used.


  1. As the comfrey decomposes it smells atrocious, much like raw sewerage and it is necessary to cover to contain the smell and prevent an invasion of flies.
  2. Put the shredded leaves and a hessian sack so that the decomposed leaves do not block the holes or tap depending on the method used.
  3. Dilute the tea before feeding to plants and do not feeding to seedlings. As a guide the darker the tea the more it should be diluted.
  4. The tea makes a ready to use liquid feed for most vegetables and an ideal substitute for commercial tomato feed (except you might need to add a teaspoon of Epsom salts per 5 litres to provide magnesium.
  5. When handling comfrey leaves one should wear gloves as they may cause irritation.

Further reading: