Eryngium serra (Sea Holly) — Clump-forming, upright and branching; some form basal rosettes

Overview

Eryngium serra 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. Eryngium serra 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, drought-tolerant plantings and winter interest.. It is native to Western Europe.

About

Eryngium serra is a perennial in the Apiaceae with leathery, often spiny leaves and an upright, clump-forming, branching habit. It favours exposed, south- or west-facing positions and performs on poor to moderately fertile, sharply drained soils such as sand, chalk or gravel. Flowering occurs June to September. Plants may be deciduous or evergreen and sometimes show silver veining on the foliage.

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 serra belongs to the genus Eryngium in the carrot family (Apiaceae) and is native to Western Europe. It grows as upright, branching clumps with leathery, often spiny leaves that can be either deciduous or evergreen; some plants show marbling or silver veining that gives foliage a distinct texture in close view. Sit the plant in full sun on free-draining substrates — sand, chalk or gravel — with a neutral to alkaline pH. It tolerates poor to moderately fertile soils but will not survive winter waterlogging, so choose a site where winter wet cannot accumulate. An exposed, south- or west-facing aspect suits it best. Hardiness is H4–H7, which in UK terms ranges from average hardy to fully hardy, so established plants cope well with cold where drainage and exposure are appropriate. Use Eryngium serra in gravel gardens, rockeries, drought-tolerant groupings and borders where its spiny leaves add structural contrast and provide winter interest. Plant it where the foliage can be appreciated at close range and allow the clump-forming habit room to branch. Expect flowering from June to September.

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 serra 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
Suggested uses: Gravel gardens, rockeries, borders, drought-tolerant plantings, winter interest.
Native to: Western Europe

Care notes

Pruning and caring for Eryngium serra

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 serra?

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 serra?

Eryngium serra prefers full sun. It suits exposed positions.

What soil does Eryngium serra need?

Eryngium serra 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 serra?

Cut spent stems back in early spring rather than autumn, since the dried heads are among the best winter silhouettes in the border.

Is Eryngium serra hardy in the UK?

Eryngium serra 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 serra?

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.

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