Marrubium incanum
silver horehound
Overview
Marrubium incanum is a mound-forming perennial in the mint family, growing 12-24 inches (30-60 cm) tall and 18-24 inches (45-60 cm) wide, with soft, woolly stems and leaves densely coated in white hairs. The oval, crinkled leaves are 1-2 inches (2.5-5 cm) long and silvery gray-green, paler beneath, releasing a faint scent when crushed. From early to midsummer, small white two-lipped flowers form in tight whorls clustered at the leaf joints along upright stems. The flowers draw bees and other pollinating insects. The silvery foliage holds through the growing season and persists in mild winters, dying back where cold is hard. Plants reach full size within two seasons. Marrubium incanum grows in full sun on poor, sharply drained soil and tolerates heat, drought, and alkaline ground once established. Rich or moist soil makes the stems soft and floppy and shortens the plant's life. The plant self-seeds where spent stems are left, and seedlings appear across open ground. The square stems may splay outward in shade or after summer rain.
Native Range
Marrubium incanum is native to the central and eastern Mediterranean, particularly the Balkans and Italy, where it grows on dry, rocky slopes and disturbed open ground.Suggested Uses
Planted in gravel gardens, dry borders, and Mediterranean-style plantings for the silver foliage, spaced 18-24 inches (45-60 cm) apart. Combined with other drought-tolerant perennials on poor soils. Suited to pollinator plantings and hot, dry sites.How to Identify
Appearance
Size & Dimensions
Height1' - 2'
Width/Spread1'6" - 2'
Reaches mature size in approximately 2 years
Colors
Bloom Information
White flowers open in tight whorls from early to midsummer, June into July, over four to six weeks. The dried seed heads remain on the stems into autumn. Bloom is heaviest on plants grown in full sun and lean soil.
Detailed Descriptions
Foliage Description
silvery gray-greenGrowing 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
Grow in full sun on poor to average, sharply drained soil, including gravel and chalk. Water sparingly during the first season; once established the plant tolerates extended drought. Cut stems back after flowering to limit self-seeding and keep the mound compact. Trim the plant in spring to remove winter-damaged growth. Rich, moist soil produces weak, floppy stems and shortens the plant's life. Sharp drainage in winter matters most, as wet soil rots the crown.Pruning
Cut the flowered stems back by about half after bloom to keep a compact mound and reduce self-seeding. Winter-damaged growth is removed in early spring as new shoots emerge. No other pruning is needed.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summer
Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons