Comfrey   Symphytum officinale   A useful herb to plant beneath fruit trees,as its deep root system draws up nutrients which are out of reach of most plants.its leaves are high in potassium,a nutrient that is benificial for activating the compost heap.A rich plant tonic can be made by steeping comfrey leaves in a bucket of water.Cover,& leave for a few weeks.This black coloured liquid is then diluted (10 to 1) and applied to any plant in your garden.