Self Heal (Prunella vulgaris) also known as ‘healall’ and ‘touch and heal’, is related to mint and is a common herb in Britain. It is most easily spotted on lawns that have not been treated with weedkiller. It has creeping, self-rooting, square stems which will send out roots at stem nodes (these are the places along the stem where leaves, branches, and aerial roots grow. They are always found at the base of a bud, leaf, twig, or branch). It also reproduces by seed.
The whole plant is edible and has been used in medicine for centuries. Before the Second World War, it was used to stop bleeding and for treating heart disease. It is still used externally for treating minor injuries such as sores, burns, bruises and can also be used as a mouthwash to treat mouth ulcers. In China it is used as an anti-cancer drug.
For more info see https://www.plantlife.org.uk/uk/discover-wild-plants-nature/plant-fungi-species/selfheal