Mentha longifolia, also known as horse mint,[1] brookmint,[2] fillymint or St. John's horsemint, is a species of plant in the family Lamiaceae.

The flowers are 3–5 mm long, lilac, purplish, or white, produced in dense clusters (verticillasters) on tall, branched, tapering spikes; flowering in mid to late summer.

Nicholas Culpeper's Complete Herbal (1653) states that "It is good for wind and colic in the stomach ...

The juice, laid on warm, helps the King's evil or kernels in the throat ...

The decoction or distilled water helps a stinking breath, proceeding from corruption of the teeth, and snuffed up the nose, purges the head.