Marrubium spp.
horehound
Mediterranean, Europe, and temperate Asia
Overview
Marrubium is a genus of about 40 aromatic perennial herbs in the mint family (Lamiaceae), native to the Mediterranean region, Europe, and temperate Asia. Plants form bushy clumps generally 12–24 in (30–60 cm) tall on square, branching stems clothed in white woolly hairs. The opposite, rounded leaves are wrinkled and grey-green, with a felted surface that reduces water loss. Whorls of small white to pale-mauve, two-lipped flowers gather in dense clusters at the leaf axils through summer. After flowering, the calyx teeth harden into tiny hooks that catch on fur and clothing, scattering the seed. The most familiar species, M. vulgare or white horehound, has been used for centuries in cough syrups, lozenges, and bitter candy, and it now grows wild across much of the world. In some regions M. vulgare is classed as a noxious weed, including parts of Australia and the western United States, where it colonizes dry rangeland. Across the genus, plants take full sun, poor dry soils, and heat, but rot in wet or shaded ground. The grey foliage carries a musky scent when crushed.
Native Range
Marrubium is native to the Mediterranean Basin, Europe, North Africa, and temperate Asia. M. vulgare has naturalized far beyond this range and now grows wild on every inhabited continent.Suggested Uses
Grown in herb gardens, gravel and dry-stone plantings, and Mediterranean-style borders for grey foliage and drought tolerance. M. vulgare is cultivated for use in cough remedies, lozenges, and bitter horehound candy. The nectar-rich flowers are kept in pollinator and bee plantings.How to Identify
Appearance
Size & Dimensions
Height1' - 2'
Width/Spread1' - 2'
Bloom Information
Flowering runs through summer, roughly June to September, with dense whorls of small white flowers at the upper leaf axils. The blooms draw bees and other insects to their nectar. Hooked seed heads follow and persist into autumn.
Detailed Descriptions
Flower Description
white to pale mauveFoliage Description
wrinkled grey-green, white-woollyGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Marrubium species grow in full sun on lean, dry, sharply drained soils, and tolerate drought, heat, and poor fertility once established. Wet winter soil and shade cause root rot and weak, sprawling growth. Plants need little feeding, since rich soil produces floppy stems. Cutting back after flowering limits self-seeding, which can be heavy in mild climates. Most species are hardy to about -20°F (-29°C) in well-drained ground. Division or seed in spring renews older clumps.Pruning
Plants are sheared back by about half after flowering to stay compact and limit self-sown seedlings. Dead stems are removed in early spring before new growth begins. Old, woody clumps are divided or replaced every few years.Container Growing
Suitable for container growing
Minimum container size: 2 gallons