Centranthus ruber
red valerian
Overview
Centranthus ruber is a bushy, short-lived perennial growing 24-36 inches (60-90 cm) tall and about as wide, with somewhat woody lower stems and a deep taproot. The blue-green leaves are lance-shaped to oval, 2-4 inches (5-10 cm) long, in opposite pairs, with smooth margins and a slightly fleshy texture. Branched clusters of small star-shaped flowers, each about 0.2 inch (5 mm) across with a slender spur, appear from May to September in shades of deep rose-red, pink, or white. The flowers are fragrant and draw butterflies and moths. Tiny seeds carry a feathery parachute that disperses on wind, and plants self-seed freely, colonizing walls, gravel, and rocky ground. Growth is fast, reaching flowering size the first year from seed. The plant tolerates poor, alkaline, and dry soils and roots into masonry cracks. It is naturalized widely outside its native range and can spread into uncultivated ground. Stems become open and lax by late summer, and cutting back renews compact growth.
Native Range
Native to the Mediterranean region of southern Europe, North Africa, and western Asia. Widely naturalized in temperate regions including the British Isles, western North America, and Australia, where it grows on old walls, cliffs, road cuts, and rocky waste ground.Suggested Uses
Used in dry gardens, gravel gardens, coastal plantings, and on retaining walls and banks, spaced 18-24 inches (45-60 cm) apart. Suits Mediterranean and low-water plantings and naturalizes in wall crevices and rocky slopes. Its prolific self-seeding makes it weedy in some regions, where it is treated as invasive.How to Identify
Appearance
Size & Dimensions
Height2' - 3'
Width/Spread1'6" - 2'
Colors
Bloom Information
Flowers from May through September, with the heaviest flush in early summer. Cutting back spent stems after the first flush brings a second bloom into autumn. Flowering runs longer in mild climates and may continue year-round in frost-free Mediterranean conditions.
Detailed Descriptions
Flower Description
rose-red, pink, or whiteFoliage Description
blue-greenGrowing Conditions
Sun Requirements
Requires 6-10 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
Grows in full sun in poor to average, sharply drained, neutral to alkaline soil, including gravel, chalk, and wall crevices. Tolerates drought once established through its deep taproot and needs no supplemental water in most climates. Rich or wet soils produce floppy growth and shorten the plant lifespan. Cut plants back by half after the first bloom to renew compact growth and trigger rebloom. Self-seeds prolifically, so removing seed heads before they ripen limits spread. Short-lived, lasting 3-5 years, but replaces itself readily from seed.Pruning
Cut stems back by one-third to one-half after the first flush of bloom to produce a second flush and keep growth compact. Shear off spent flower heads to reduce self-seeding. Cut the whole plant to the base in late autumn or early spring to remove old woody stems.Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons