Mentha piperita citrata or Lemon Mint is a hardy, upright, spreading, rhizomatous perennial herb grown usually as a ground cover or as a constituent of a herb garden.
It bears pale mauve flowers in early summer and the lance shaped, dark green leaves have small glands which hold the pungent oils for which it is valued. Aromas are mixed and include mint and citrus - either orange or lemon.
Good for infusions or as an inhalant and excellent in pot pourris.
A deservedly popular occupant of many a herb garden that is easy to keep, though you'll need to keep it contained so as to not spread uncontrolled.