Overview
Eryngium planum is a clump-forming, upright and branching; some form basal rosettes perennial in the genus Eryngium, part of the Apiaceae family, with deciduous or evergreen; leathery, often spiny, sometimes marbled or silver-veined foliage. It typically grows around 0.7 m tall. Eryngium planum grows best in full sun, and tolerates most soils and neutral to alkaline pH. Its UK hardiness is rated H4-H7. Suggested uses include gravel gardens, rockeries, borders, cut flowers and dried flower arrangements. It is native to Central Europe to W Himalaya.
About
Eryngium planum is a clump-forming perennial notable for its steely-blue stems and tightly packed blue flowerheads set within spiny bracts. Plants form upright, branching clumps often with leathery, sometimes silver-veined leaves. Flowering runs from June to September, producing stems about 0.7 m tall that are useful fresh or dried. It favours sunny, sharply drained sites on neutral to alkaline soils.
Wikipedia contributors, CC BY-SA 4.0 — Eryngium planum
About the genus
Eryngium is a genus of flowering plants in the family Apiaceae. There are about 250 species. The genus has a cosmopolitan distribution, with centres of diversity in the western Mediterranean, South America and Mexico.
Wikipedia contributors, "Eryngium", CC BY-SA 4.0 — Eryngium
In the garden
Eryngium planum originates from central Europe eastwards to the Himalaya and carries the thistle-like look associated with sea hollies. It forms upright, branching clumps or occasional basal rosettes, bearing leathery leaves that may show silver veining and many conical blue flowerheads surrounded by spiny bracts. Flowering is from June to September and stems reach roughly 0.7 m. Plant it in full sun on sharply drained sand, chalk or gravel, ideally on a south or west-facing, exposed site. It tolerates poor to moderately fertile conditions and prefers neutral to alkaline pH; avoid winter waterlogging, which the species cannot survive. The hardiness range given (H4–H7) means it is suitable from average to fully hardy parts of the UK, so choose free-draining locations in colder or wetter districts. Use Eryngium planum in gravel gardens, rockeries and sunny borders where the spiky flowerheads add structural contrast, and cut stems for summer arrangements or drying. Sit it with other drought-tolerant perennials on a sunny edge where the blue flowerheads catch light and the silvery foliage provides season-long texture. Stems are long-lasting when cut and are commonly used in dried floral work.
Growing conditions
Best soil and position for Eryngium
- Sunlight
- Full sun
- Soil type
- Poor to moderately fertile, sharply drained sand, chalk or gravel
- Soil pH
- Neutral to alkaline
- Soil moisture
- Well drained to dry; winter wet is fatal
- Aspect
- South or west facing
- Exposure
- Exposed
- UK hardiness
- H4-H7
Plant details
Eryngium planum size, habit and characteristics
- Plant type
- Perennial
- Habit
- Clump-forming, upright and branching; some form basal rosettes
- Foliage
- Deciduous or evergreen; leathery, often spiny, sometimes marbled or silver-veined
- Height
- 0.7 m
- Suggested uses
- Gravel gardens, rockeries, borders, cut flowers, dried flower arrangements
- Native to
- Central Europe to W Himalaya
Care notes
Pruning and caring for Eryngium planum
- Cultivation
- Give them the hottest, poorest, best-drained position in the garden. Rich soil produces soft growth that flops and rots, so resist feeding. Most resent disturbance because of a long taproot, which is also what makes them genuinely drought-tolerant once settled - plant young and leave alone. Excellent in gravel gardens and on thin chalk.
- Pruning
- Cut spent stems back in early spring rather than autumn, since the dried heads are among the best winter silhouettes in the border.
- Propagation
- Sow seed fresh in autumn, as germination becomes erratic once stored. Root cuttings taken in winter are the reliable route for cultivars; division rarely succeeds given the taproot.
- Pest resistance
- Slugs damage young growth, particularly on the rosette-forming species; otherwise little troubled.
- Disease resistance
- Healthy where drainage is adequate. Root and crown rot follow winter waterlogging, which is by far the commonest cause of loss.
Frequently asked questions
How do I grow Eryngium planum?
Give them the hottest, poorest, best-drained position in the garden. Rich soil produces soft growth that flops and rots, so resist feeding. Most resent disturbance because of a long taproot, which is also what makes them genuinely drought-tolerant once settled - plant young and leave alone. Excellent in gravel gardens and on thin chalk.
Where is the best place to plant Eryngium planum?
Eryngium planum prefers full sun. It suits exposed positions.
What soil does Eryngium planum need?
Eryngium planum is adaptable and grows happily in most soil types, including poor to moderately fertile, sharply drained sand and chalk or gravel. It prefers neutral to alkaline soil. Aim for soil that stays well drained to dry; winter wet is fatal.
How do I prune Eryngium planum?
Cut spent stems back in early spring rather than autumn, since the dried heads are among the best winter silhouettes in the border.
How big does Eryngium planum grow?
Eryngium planum reaches a height of 0.7 m.
Is Eryngium planum hardy in the UK?
Eryngium planum has an RHS hardiness rating of H4, meaning it is hardy through an average UK winter, tolerating -10 to -5°C.
How do I propagate Eryngium planum?
Sow seed fresh in autumn, as germination becomes erratic once stored. Root cuttings taken in winter are the reliable route for cultivars; division rarely succeeds given the taproot.
More in the Eryngium genus
- Eryngium agavifoliumSea Holly
- Eryngium bromeliifoliumpineapple-leaved eryngo
- Eryngium eburneum
- Eryngium horridumSea Holly
- Eryngium planum 'Blaue Kappe'Blue Eryngo
- Eryngium planum 'Seven Seas'Blue Eryngo
- Eryngium proteiflorumprotea-like-flowered eryngo
- Eryngium serraSea Holly
