As I keep my eye on the lush growth of the tomato, my thoughts turn to feeding these hungry plants. This is something that I will be doing every two weeks or so as soon as the plants start to produce fruit.

Rather than buying liquid feeds, for some years now I have been making my own organic version by soaking the leaves of the comfrey plant. Comfrey is a perennial herb with big, broad, hairy leaves that produce small purple flowers.

It has long been used as a feed by organic gardeners, particularly the variety “Bocking 14”, named after the town of Bocking in Essex, which was the original home of the organic gardening research association, Garden Organic.

Comfrey is a remarkably fast-growing plant and is one of nature’s great “miners”. It sends its roots deep into the soil and brings up nutrients – most notably potassium – from deep in the subsoil.

It is this nutrient, in particular, which will be of benefit to the tomato plants, and in fact all fruiting vegetables in the garden (including pumpkins, courgettes and squash).

The basic idea of making a comfrey tea is to harvest leaves and soak them in water for about a month. This potassium-rich “tea” is then applied as a feed to fruiting plants.

I use a shears and literally cut the plant down to about two inches from the surface of the soil. Put on a pair of gloves, as the leaves are a little prickly.

You can harvest mature comfrey plants three to four times each year. It grows back quickly and can be cut again about a month later.

You should be able to source the plants from a good garden centre and then plant them out about two feet apart. They will tolerate a shady, even damp, spot in the garden. Mine are thriving in a corner of the garden behind the tunnel.

Keep the bed well watered until the plants get established and don’t harvest leaves from it in the first year.

Strangely, comfrey doesn’t seem to be able to mine the nitrogen that it needs for itself very well, being a fast-growing leafy plant (similar to a brassica). I generally mulch the plants with lawn clippings when they die back in the autumn.

In addition to making a comfrey tea, you can also add comfrey leaves to the compost heap, where they will accelerate the de-composition of your heap and add potassium. You can also use the leaves as a mulch, putting a layer of leaves around a plant where they will break down and release their nutrients more slowly.

I’ve heard of people putting comfrey leaves in a trench when planting potatoes and also planting comfrey underneath fruit trees as a companion plant. CL

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