Lilac flowers in whorls make this wildflower quite similar at a first glance to Water Mint but it is the ground which it grows on which helps to confirm the identification. Generally found on arable ground, paths and open woodland, Corn Mint doesn't grow quite as tall as Water Mint and it has no terminal head of flowers. The little two-lipped lilac-coloured flowers (3-4mm long) have protruding stamens and are borne in dense whorls which are at intervals along the stems and emerge from axils of the leaves which themselves are longer than the flowers. They bloom in August and September. These oval, toothed, pale green leaves are stalked, hairy and opposite. Mentha arvensis is known to hybridise with Mentha aquatica, is a native plant and it belongs to the family Lamiaceae.
My first record of this plant is in 2007 at Gibletstown, Co Wexford when I also photographed it.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre