Compressed Comfrey Tube.
The bucket would normally be covered with polythene to prevent it filling with rain water
Comfrey grows wild on many allotment sites as is a fast growing (and spreading) perennial) which will given half a chance take over the whole site. For this reason I would recommend buying root cuttings of the Bocking 14
variety. Do not take root cuttings from other plants unless you know it is B14 or it has been grown in situ for a number of years and has not made a take over bid for the site.
Comfrey is the most popular of these teas and we would recommend all composters to make it to supplement their composting and compost teas.
Comfrey is a good source of potassium and nitrogen. Comfrey tea
promotes the development of flowers and fruit and is best applied once the first flowers have set. It is recommended for use on tomatoes and peppers.
The most common method of making comfrey tea involves soaking the
leaves in water but this is the method that produces the famous stinking liquid feed. A barrel or tub is quarter filled with comfrey leaves topped up with water and allowed to stand for 3 to 5 weeks. To make a good concentrated fertilizer the leaves
should be pressed down into the container by a weight of top such as a brick of broken paving slab.
Either use a container with a tap, a hole in the bottom, so that the fertiliser drips into a catch-pot, or remove the liquid
from above with a watering can. A Bokashi bin makes an excellent container in which to ferment comfrey tea as the filter tray prevents the leaves from blocking the drain tap and the airtight lid contains the smell.
There are two approaches to maintaining a supply of feed through out the summer. Either keep replacing the water as it is used and top up the supply of comfrey ever two or three months. Or once the liquid is used add the sludge to the compost
bin, to help keep it moist and as an activator, and start again using the fresh growth that has replaced that which you cut.
Be warned comfrey liquid produced in this way smells very unpleasant.
Use the tea diluted, one part tea to three parts water, for established plants, either watering into soil or as a foliar spray. For younger tender plants, such as tomatoes dilute one part tea to ten parts water and only water into
the surrounding soil or you may scorch the plants.
Concentrated comfrey tea
Concentrated Comfrey tea has the advantage of not smelling anywhere near as much
as the dilutes version. I recommend that it is made using a drainage pipe fiited with an end cap through which a single drainage hole has been drilled. Comfrey leaves are compressed in the pipe using a plastic bottle filled with sand or water or a sparking
wine bottle which is heavier and more fun to empty before use in the tube.
Larger quanitities of concenrated comfrey tea can be made by packing comfrey leaves into a barrel or a similar container with a tap, preferably
compressing the comfrey down with a spade to get the maximum amount into the barrel and compressing it with a weighted lid. Only add a small volume of water or urine and water to get the flow going. This method is recommended by Nicky Scott in How to Make
and Use Compost (Green Books 2009)