Comfrey is a perennial plant that is very easy to grow. Fast-growing, it sends down deep roots and is known as a dynamic accumulator because it can find nutrients in deep soil, bring them up and store them in its leaves. Its natural habitat is along riverbanks, and the wild plant has white flowers and spreads very easily by seed.
Many varieties can quickly become weeds in a garden because they spread by seed, but there is a sterile cultivar, called Bocking 14, that is ideal for gardens as it does not set seeds – it is propagated from root cuttings or division of a mature plant. Bocking 14 has beautiful, purple flowers that attract bees.
Comfrey establishes easily, and if you have bought a root cutting or been given a section of a plant by a friend then all you need to do is plant it and keep it watered until it has started to grow. Root cuttings are generally available from May to August, and should be planted as soon as they are bought. If a permanent site is not available then you can pot them up in the meantime.
Comfrey will grow on any type of soil, but its leaves will be more nutritious (and plentiful) if it is grown on good soil. A good place to grow your plant is around the base of a compost heap, where it can “mop up” any plant nutrients that are washed out of the compost.
A well-established plant will grow a lush set of leaves that can be cut several times during the growing season. The first cut is often used to line the planting holes for potatoes. Leaves break down very rapidly, which means that they can also be used as a mulch that will provide a supply of nutrients to growing crops as well as suppressing weeds and preventing water loss through evaporation.
Leaves work as a compost activator, and if added to a compost heap they will help speed up the composting process as well as adding its nutrients to the compost.
Comfrey leaves are high in potash, a valuable plant food that is ideal for potatoes and fruiting plants like tomatoes and peppers. It is easy to make them into a liquid feed that is easily applied to vegetables and rapidly absorbed by plants.
One way to make comfrey into a liquid feed is to soak the leaves in a bucket of water for several weeks, until they begin to decompose. The smell this creates is amazing – you will think that the local water company has opened a new sewage treatment plant at the bottom of your garden! You will need to dilute the liquid before you use it.
A less odorous way to achieve the same end is to put the leaves in a lidded container (squash them in well and weigh them down with a stone) and let them break down on their own over the course of several weeks. If your container has a tap then it will be easy to draw off the resulting dark brown liquid when it is ready.
The remains of the leaves can be added to the compost heap. This type of comfrey liquid will store well in a bottle until you are ready to use it. You need to dilute it well before applying it to plants: try a 1:10 ratio for established plants, and don’t forget to water them first – liquid feeds should never be applied to dry soil.
This is one of a series of basic gardening articles that you might be interested in. You can learn more about comfrey, the permaculture plant, or listen to the comfrey episode of the Alternative Kitchen Garden Show. Have a look at my ‘Circle of Life’ garden plan, which incorporates a comfrey tower, or find out more about turning weeds into liquid feeds. For more about feeding plants and caring for you soil, buy my book: The Peat-Free Diet.