Comfrey

comfrey organic gardening

Comfrey is the organic gardener's best friend. Its leaves are full of nitrogen, phosphorus and potassium - all nutrients needed by growing plants. Master the use of comfrey and you'll never need to buy expensive fertiliser again.

On this page we tell you:

How to make comfrey liquid fertiliser
Follow these simple steps:

  1. Cut off the leaves about 5 cms above soil level. Wear gloves, as the stems are covered in stiff hairs that can irritate the skin.
  2. Fill a bucket or barrel with water and add approx 1kg of cut or bruised leaves to every 15 litres of water. You needn’t be too precise!
  3. Press the leaves down firmly so they are covered with water, and cover the container.
  4. After 4-6 weeks a noxious (very) smelly brown liquid is ready for use. There is no need to dilute.
  5. Strain off the sludge at the bottom, and put it on the compost heap.

To make a concentrate, you don’t need water.
You will need: • 2 litre plastic drinks bottle, without a cap  • a collecting vessel – large yoghurt pot, ice cream carton or similar

  1. Turn the bottle upside down and cut off the bottom.
  2. Pack in the cut and bruised comfrey leaves so the bottle is full. Press them down firmly.
  3. Cover the open end with a polythene bag, held in place with an elastic band, to prevent drying out.
  4. Stand/fix/wedge the bottle upside down so that it will drip into your collecting vessel.
  5. As the leaves rot, a brown comfrey liquid will drip out of the bottle into the collecting vessel below.
  6. Add fresh cut/bruised leaves, pressed down firmly, into the bottle, to keep a constant supply of rotting material
  7. This concentrate should be watered down according to its strength – when thick and black, dilute 1 part feed to 20 parts water; when thin and brown, dilute 1 to 10. You needn’t be too precise.

How to use comfrey liquid fertiliser
Use as a summer feed for: tomatoes, peppers and cucumbers (apply as soon as the flowers have set fruit)
For hanging baskets and pot plants
For other hungry flowering plants such as clematis and dahlias.

Other ways to use comfrey leaves:

  • Place cut or bruised comfrey leaves in alternate layers throughout your compost heap. Their decomposition will encourage bacterial action causing the heap to heat up and speed up the composting process.
  • Use as a mulch.  Chop up comfrey leaves with grass cuttings, and place a 5cm layer on the surface of the soil around all plants. This will slowly rot down to provide nutrients, and act as a mulch to keep in moisture and help control weeds.
  • Add fresh cut leaves to your leaf mould heap. Their nutrient-rich liquid will be absorbed, making it a perfect medium for growing seeds and potting compost.
  • Fertilise the bottom of your potato and and runner bean trenches with a layer of comfrey leaves. As they break down, the plant roots will access the potassium-rich fertiliser.

How to grow comfrey
Garden comfrey has a higher nutrient content than the common wild comfrey, and its leaves can be cut several times in a season. Our research found that the ‘Bocking 14’ variety is the best. Available from The Organic Gardening Catalogue, Garden Organic members get a 10% discount.

  • Choose your site carefully – comfrey can live for 20 or more years. It is too vigorous to grow in a pot, but it will grow on most soil types (except the very shallow and chalky), thriving in good soil in the full sun.
  • Allow 60–90 cm between plants.
  • Once established, it needs very little maintenance, however to maximise your comfrey crop, extra feeding with manure and compost or grass clippings will all help to produce more leaves.
  • If you plant cuttings in spring you will be getting your first leaf harvest before the end of the growing season.
  • Remove flowering stems in the first season to gain maximum leaf growth next year.