Mentha cervina aka Hart's Pennyroyal

Mentha cervina, or hart's pennyroyal, belongs to the mint family, Lamiaceae. It is a perennial from the Azores and western Mediterranean. Its range includes Portugal, Spain, southern France, and Morocco. It grows in damp places within this temperate region. It is not native to Britain or Ireland. Preslia cervina is another name used for this species.

This bushy plant forms clumps and keeps some leaves through winter. Its narrow, lance-shaped leaves have a strong spearmint scent. The RHS describes plants about 1 foot (0.3 m) tall. Its size range allows heights of 1.6 feet (0.5 m). The spread can also reach 1.6 feet (0.5 m). Plants take two to five years to reach full size. Pale blue or lilac flowers grow in whorls. They appear from midsummer and continue into autumn. The scented leaves and summer flowers suit wildlife gardens.

Grow this mint in soil that stays moist all year. It can also grow in shallow water. The RHS allows water depths of about 0.3 feet (0.1 m). Choose full sun or partial shade. Clay and loam both suit it, including poorly drained sites. It accepts acid, neutral, and alkaline soil. These needs make it useful in bog gardens and damp beds. The RHS gives it a UK hardiness rating of H7. Plants For A Future lists USDA zones 6–9.

Divide clumps in spring to make more plants. Cut the growth back once flowering ends. Watch its spread, since the RHS warns it can become troublesome. Plants For A Future does not flag it as weedy. These accounts suggest that garden conditions may affect its behaviour. The RHS reports few pest problems. Powdery mildew and mint rust can still affect the plant. Its need for lasting moisture matters when choosing a planting site.

The leaves can make a herb tea with a mint scent. Plants For A Future gives it an edible-use score of three out of five. It also records essential oil extraction from the whole plant. Its medicinal-use and other-use scores are both two out of five. The source reports no known toxicity records for this species. That does not establish safety for every use or dose. Its broader warnings about other mints do not establish this species' toxicity.