Comfrey is an ancient plant that has had many documented uses over the centuries. We are primarily concerned with the use of comfrey in the garden and allotment – please refer to the search engine of your choice to research other uses of comfrey.
Once harvested, comfrey leaves and stems have a characteristic that makes them ideal for horticultural use – they decompose quickly and easily into a nutrient-rich liquid. We can take advantage of this characteristic by using the leaves as they are, for example as a slow-release fertiliser in a potato trench, or by capturing it in the preparation of liquid feed.
Be aware that comfrey leaves and the liquid they produce are alkaline, and can increase the pH of your soil if used regularly in large quantities. We recommend testing your soil at least every 3 years, and not using comfrey on acid-loving plants like blueberries.
Comfrey liquid fertiliser
Probably the most popular use of comfrey, this simple process will produce a concentrated liquid plant food as good as any commercial organic alternative, for free.How to make comfrey liquid
This is not a tea for you to drink! It is a liquid fertiliser for your garden, to be applied to plants or the soil. If you don’t have enough comfrey, patience, or time to make concentrated comfrey liquid, this “comfrey tea” is a viable alternative.How to make comfrey tea
Comfrey as a mulch
Comfrey makes an excellent mulch, especially on vegetable beds and around fruit trees and bushes.
Apply a two-inch layer of comfrey leaves on the surface of the soil. The leaves will slowly decompose, releasing valuable nutrients for the crop, and a little humus. The layer of comfrey can also be covered in turn with an inch of grass clippings, helping to retain moisture, accelerate the decay of the comfrey, and a more effective weed suppressant.
Comfrey in a potting mixture
This recipe from HDRA for a potting ‘compost’ is a great use of comfrey if you have a source of leafmould.
The leafmould needs to be well rotted (at least 2 years old), and passed through a coarse sieve before use.
We make this ourselves in bins every year and have had excellent results with it:
- In a black polythene sack or plastic dustbin, alternate 3-4 inch layers of fine leafmould and chopped comfrey leaves, and firm down gently. Avoid flowering stems as they rot down too slowly. If the leafmould is damp, it is a good idea to wilt the comfrey before adding it otherwise the mixture can get too wet.
- Leave for 2-5 months, depending on the season, checking that the mixture does not become too wet, or dry out. If too wet, turn it out and let it dry out before returning it to the container. If too dry, spray with water and mixt well.
- The mixture is ready when the comfrey leaves have rotted down and virtually disappeared; you may still be able to see a few bits of stem.
- Use as a general potting compost. For very demanding plants you may need to add extra nutrients; for seedlings and sensitive plants you will need to dilute it 50:50 with additional sieved leafmould.
The resulting compost is comparable with commercial compost, but may not be as water retentive and need watering more often than you are used to.