Confused by comfrey

Masterclass on: making more of comfrey

- ANNE SWITHINBANK

Q A friend has given us a division of comfrey, which is now a tall, hairy plant with purple flowers. We were told we could make a plant feed from its leaves, but how – and when? Andrea Marshall, Peterborough, Cambridgeshire

A This gift is hopefully the type of Russian comfrey (Symphytum x uplandicum) known as Bocking 14. Unlike some other comfreys, including the common sort (S. officinale) it does not set seed and won’t spread.

Thick roots reach deep into the soil, drawing on nutrients untapped by most other plants. These are stored in the leaves, which when harvested are used as compost heap fodder, as a mulch over moist soil around plants or rotted down to make a stinky brew. This is well known as a high-potash liquid feed but also supplies nitrogen, phosphorus, magnesium and calcium.