How to make comfrey tea

If you want to promote flower and fruit growth in your garden or your allotment you can make your own liquid feed by making a batch of comfrey tea. It's easy to make and once you have the comfrey plants they provide a free and sustainable organic fertiliser which contains the same nutrient values as tomato feed, and the leaves can also be used in the compost heap to speed up decomposition.

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Find out how to make a compost heap

Growing comfrey

Comfrey plants can be invasive, so try to buy Symphytum uplnadicum ‘Bocking 14’ because this is a sterile clone of Russian comfrey which does not set seeds. Position close to a compost heap, or in a wilder area of the garden, with plenty of space around it as a mature plant can get quite large and live for 20 years.

Allow it to flower because this member of the borage family produces nectar-rich flowers in May, just when other flowers are in short supply.

After flowering cut the leaves off from the base to leave a stump. Chop the leaves up roughly and make the first batch of comfrey tea. Repeat the process throughout summer. You should be able to get at least four cuts.

How to make comfrey tea

Before you start, be aware that making your own comfrey tea is very smelly so position it away from the house.

After flowering chop your comfrey leaves and place into a bucket. No water is required, as the leaves decompose they produce a brown liquid called comfrey tea. 

Within days an evil-smelling slurry is created. Once the decomposition process is complete (after about two weeks) dilute the liquid - one part tea to twenty parts of water. Once diluted, it is fairly pleasant to sniff.

Where to use comfrey tea

Comfrey tea has the same nutrient values as tomato feed and it’s free - as long as you can put up with the stench as it decomposes.

Comfrey tea can be used an all crops and in hanging baskets and containers and is excellent for promoting fruit and flower, but you do need to acquire Bocking 14 - this has the correct nutrients for the job.

Use comfrey tea once a week to promote more flowers and fruit.

Read our guide on what to feed plants

Other uses for comfrey leaves

You can also chop up any comfrey leaves and add them to your compost heap as an accelerator, just make a layer of comfrey leaves to speed up decomposition, or you can put them at the bottom of potato trenches as a food for your crop.

The history of comfrey tea and Bocking 14

Bocking is a village near Colchester in Essex. The benefits of growing comfrey were discovered by Henry Doubleday (1810-1902), who had a smallholding there. He was a starch manufacturer who tried to utilise the mucilaginous properties of comfrey roots to make the first patented glue for postage stamps. Previously, the sticky paste had been used to heal broken bones giving comfrey (or symphytum) the common name of knitbone.

Henry, who never cracked the glue making in time to patent it, imported several types of Russian comfrey (Symphytum uplandicum) and gave them numbers. 

He discovered that comfrey stayed in leaf for 10 months of the year and wrote about this in the Gardener’s Chronicle and Agricultural Gazette. Years later the famous organic gardener Lawrence Hills (1911-1991) discovered the articles and visited Bocking where he found Henry’s children nonagenarians Edith and Thomas, in residence - still growing comfrey.

Lawrence Hills, founder of Garden Organic, tested twenty numbered forms and found Bocking 14 the best because the leaves contain twice as much potash as ordinary comfrey (Symphytum officinale). In fact it is the best source of natural potassium available to gardeners.

Read our guide to improving your soil

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