Eryngium planum 'Seven Seas' (Blue Eryngo) — Herbaceous perennial

Overview

Eryngium planum 'Seven Seas' is a herbaceous perennial in the genus Eryngium, part of the Apiaceae family. It typically grows around 0.7 m tall. Eryngium planum 'Seven Seas' grows best in full sun, and tolerates most soils. Its UK hardiness is rated H7. Suggested uses include mid-border and gravel planting.

About

Eryngium planum 'Seven Seas' is a herbaceous perennial in the Apiaceae with thistle-like flowerheads composed of small blue cones surrounded by spiky bracts. Stems are branched and silvery-blue, carrying the flowerheads above a basal rosette. Flowering runs from June to September. The cultivar presents a compact habit, typically suited to mid-border or gravel planting.

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 'Seven Seas' belongs to the Apiaceae and follows the species’ characteristic of producing conical, blue flowerheads encircled by stiff, spiny bracts. The species originates from countries across central and south‑eastern Europe and into Central Asia, where it grows as a short-lived herbaceous perennial. In the garden it appears as a multi‑stemmed plant with silvery‑blue, branched stems bearing the distinctive inflorescences. Plant where the architectural flowerheads can be seen; place individual plants so the spiky bracts and cones are not hidden by taller neighbours. Keep soil free‑draining and avoid waterlogged hollows to preserve stem integrity and flowering potential. Cut back stems after flowering to tidy the clump and allow fresh basal growth the following season. Labels and nursery descriptions will indicate whether a specific cultivar tolerates the conditions in your plot. Use 'Seven Seas' where the blue flower colour and sculptural bracts will be visible from paths or patios: gravel beds, the front to middle of mixed borders and sunny, open positions suit its sculptural habit. The blue conical flowerheads and spiky bracts give clear summer punctuation from June to September.

Growing conditions

Best soil and position for Eryngium

Sunlight: Full sun
Soil type: Sandy, Loamy, Clay
Soil moisture: Well-drained, Moist but well-drained
Aspect: Sunny
Exposure: Full sun
UK hardiness: H7

Plant details

Eryngium planum 'Seven Seas' size, habit and characteristics

Plant type: Herbaceous perennial
Height: 0.7 m
Suggested uses: Mid-border, Gravel planting

Care notes

Pruning and caring for Eryngium planum 'Seven Seas'

Cultivation: Prefers well-drained soil; drought tolerant once established; avoid waterlogged conditions
Pruning: Remove spent flower heads to encourage tidy appearance; cut back in late autumn or early spring
Propagation: Seed, Division

Frequently asked questions

How do I grow Eryngium planum 'Seven Seas'?

Prefers well-drained soil; drought tolerant once established; avoid waterlogged conditions.

Where is the best place to plant Eryngium planum 'Seven Seas'?

Eryngium planum 'Seven Seas' prefers full sun. It suits full sun positions.

What soil does Eryngium planum 'Seven Seas' need?

Eryngium planum 'Seven Seas' is adaptable and grows happily in most soil types, including sandy, loamy and clay. Aim for soil that stays well-drained to moist but well-drained.