This perennial species is a member of the mint family and is one of the "true mints" of the genus Mentha. It has tiny white, pale violet, or lavender flowers clustered in circles in the leaf axils around a square stem. It is the only native mint species in this area, though it is also native in much of temperate Europe and Asia.

Sometimes the North American plants are put into different subspecies. These small (1/8 inch) flowers are bell-shaped, 4 or 5-lobed and nearly symmetrical, though the upper lobe may be larger. The opposite, serrated leaves show a lot of variation but generally are ovate in shape and about 2 inches long, tapering at both ends. The leaf veins are conspicuous. The leaves are glandular and highly aromatic with a strong mint smell.

The plant grows 6-24 inches high in damp soil or along shorelines. The hairy stem may or may not have a few side branches. If there are side branches they may become longer than the main stem as the plant matures. Like most mints, this species has a stem that is square in cross-section. It is widespread in North America except from Florida west to Louisiana and Oklahoma and the Arctic. The blooming period is June to October.

Sometimes field mint hybridizes with other mints, including spearmint. The Eurasian subspecies have also naturalized in North America and sometimes it is difficult to find a true native plant. The leaves have long been used as a flavoring in sauces, jellies, and beverages. The leaves can be made into tea and sometimes used as herbal medicine. If the leaves are chewed they produce a hot taste. The plant is generally resistant to disease and the strong mint odor deters most herbivores. Sometimes this plant is grown in gardens but can be highly invasive, spreading by rhizome.