Comfrey

Fantastic liquid feed and compost activator

By Melanie Matthews

A real wonder plant - comfrey is a fantastic source of goodness for your garden.  The plant's deep roots accumulate potassium from subsoil. Its leaves are high in nitrogen too.

How to make Comfrey tea

You can make a concentrated liquid containing all of the big 3 nutrients: nitrogen, phosphorus, and potassium, in substantial amounts.

  • Grow a bed of comfrey (best to get the variety Bocking 14, which will not self-seed and become a weed); good in compost, as a green manure.  
  • Place the plant's leaves into a large container, preferably one with a tap or hole at the bottom, and a tight lid at the top to exclude water and flies as well as keep any smell inside. Fill the container with leaves.  Cut the leaves before the flower buds appear and before the ageing leaves develop infections.
  • A block of wood and a brick could be placed on top of the pile to press it firmly and gently down, (without crushing). Fresh Comfrey leaves contain more nitrogen than farmyard manure and a black liquid smelling of ammonia will soon collect in the bottom. It is drained off into a screw topped collecting bottle. The solution needs to be diluted 15 - 20 times with water before application in the garden
  • The liquid is a versatile fertilizer, easily stored and transported, and applied to plants by watering or spraying. The nutrients it contains are readily available and it should therefore be applied carefully in small quantities or it will be wasted.
  • Or fill a bucket with comfrey leaves (nettles are good too), cover with water, and leave to stew .    Leave it for 2 to 4 weeks, and you will have a very potent brew, which should be diluted with at least 10 parts water.     The foul-smelling liquid gives an excellent plant food.  

Where to use Comfrey

  • Use liquid fertiliser for promoting flowers and fruit - use as tomato or pepper plant feed (after the first flowers have set)
  • Use liquid for container grown flowers (delay application until the plants have grown a good set of leaves)
  • use wilted leaves (not stems - they might root) in your potato trenches
  • lay leaves on the surface as a mulch around fruit bushes
  • Spread a 2" layer of fresh Comfrey leaves over the top of a new compost heap, give a sprinkling of water, and cover this with a thin layer of fine soil. The fresh leaves contain more nitrogen than farmyard manure.  So adding it to compost will quickly get the microbes busy.

Growing Comfrey 

The ideal site is sunny and over deep soil, but most soils will work except shallow chalky soils. The plant's fleshy black roots grow down deep to the subsoil where they absorb potassium.

Space plants 2-3 ft apart (1-2 ft on poor soil). When the plants are established sow Clover between and leave the cut Clover as a mulch.  The patch might be conveniently situated near to your compost heap but preferrably in a sunny position.

You will find that once established a Comfrey plant will be hard to get rid of (see eradication method below).  So before you plant it you need to decide on a permanent growing position for a plant that has an expected lifetime in excess of 20 years.

Plants used for garden cultivation are usually taken from the Bocking cultivar of Russian Comfrey (Symphytum x uplandicum) exported to U.S.A. and Canada in 1954. This plant rarely sets seeds and so it won't infest your garden. Any of the plants offered for sale from seeds are unlikely to be suitable, at least not for the purposes described on this page. Look for Comfrey sold as root cuttings or offsets.

The plant roots or offsets are set out from March to May or in September.  Place offsets with a growing points just under the surface or roots about 2" deep. Keep watered for a few weeks until plants are growing.

Harvesting Comfrey

In the first season of a newly established plant cut once in June prevent flowering and allow the plant to grow and die back so as to build up reserves. Then cut plants before flowering in April when about 2ft high. Don't cut later than September to allow the plant to recover food reserves before Winter dormancy. As plants become strong they will be ready for cutting every 4 or 5 weeks giving 3 to 5 cuts per season.

Getting rid of it!

The plant can regenerate from pieces of its roots, and these grow deep. Choose dry sunny conditions to dig the whole plant up taking care to remove all roots from the soil. Then persist in cutting down any new growths as soon as they appear until the plant is erradicated. This could take a couple of years depending on how thorough you are.

This page was added by Melanie Matthews on 02/11/2009.
Comments about this page

I've just taken over an allotment plot smothered in luscious comfrey plants. Now I know how to make use of them! Thank you.

By Tarka
On 19/10/2011