Acts as a dynamic accumulator with a deep tap root up to 3 metres long (10') that draws minerals and nutrients from the subsoil into its leaves. Chop and drop the leaves three or four times in a growing season for an effective living mulch. Often planted around the base of a tree to suppress weeds. Although most comfrey is considered invasive, this Russian type is not spread by seed. Disturbing the roots by digging up plants will instigate multiplication. Bocking 4 is rust-resistant and is noted for having the highest protein content. It is also the recommended variety for fodder, especially for poultry and pigs. Grows up to 60-90 cm (24-36”) tall.