How to Care for Pennyroyal

Pennyroyal (Mentha pulegium) is a low-growing member of the mint family with small rounded leaves and whorls of tiny lilac flowers on creeping stems. Grown ornamentally as a fragrant groundcover, it spreads readily and thrives in moist, sunny to partly shaded spots.

Light

Pennyroyal grows well in full sun to partial shade. In cooler climates it takes full sun happily, while in hot regions a bit of afternoon shade prevents the shallow-rooted mat from scorching and drying out. Ample light keeps growth dense and encourages summer flowering.

Water

Like most mints, pennyroyal likes consistently moist soil and dislikes drying out. Water regularly, especially in sun and heat, to keep the low mat lush. It tolerates damp ground better than most herbs and can even edge boggy areas, but it should not sit in stagnant water.

Soil & Potting

Grow in average to rich, moisture-retentive soil that still drains reasonably. Pennyroyal is not fussy about fertility and adapts to many soils as long as moisture is steady. In containers use a standard potting mix; growing it in a pot is a good way to enjoy its spreading habit without letting it colonize a bed.

Humidity & Temperature

A hardy perennial in temperate zones, pennyroyal tolerates a wide range of temperatures and dies back in winter to return in spring. It appreciates moderate to high humidity and cooler conditions. In very hot, dry air the foliage can crisp, so keep it moist and lightly shaded in such climates.

Feeding

Pennyroyal needs little feeding. In poor soil, a light application of balanced fertilizer or a topdressing of compost in spring supports vigorous growth. Avoid heavy feeding, which produces weak, sprawling stems and dilutes the plant's compact, mat-forming character.

Propagation

Pennyroyal is very easy to propagate. Its creeping stems root where they touch the soil, so you can divide established clumps or lift and replant rooted runners. Stem cuttings root readily in water or moist soil, and it can also be grown from seed sown on the surface in spring.

Repotting / Pruning

Shear or mow the mat after flowering to keep it tidy and encourage fresh, dense regrowth. Because it spreads aggressively by runners, contain it in a buried pot or with edging to prevent it from overtaking neighbors. Divide and repot container plants every year or two when they become crowded.

Common Problems & Pests

Pennyroyal is generally trouble-free. Its main fault is vigorous spreading, so manage runners to keep it in bounds. Rust and mint-family fungal diseases can appear in crowded, damp, poorly ventilated plantings; thin growth and improve airflow. Watch occasionally for aphids and spider mites in dry conditions.

Seasonal Care Tips

Plant in spring once frost has passed. Keep the soil moist through summer and shear back after bloom for a neat mat. In fall the plant slows and dies back; a light mulch protects the roots over winter in colder zones, and fresh growth emerges in spring.