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How to Grow Sea Holly — Eryngium

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Eryngium–commonly called sea holly–is an upright perennial with heart-shaped, divided green leaves. In summer, it produces tall blue stems topped with cone-shaped purple flowers surrounded by spiny bracts.

Eryngium is stiff-branched and thistle-like. There are 230 species in the Eryngium genus; some are fibrous-rooted and some are tap-rooted. Eryngium self sows.

Eryngium is an excellent cut and dried flower.

Alpine sea holly, Eryngium alpinum

Get to know Eryngium

  • Plant type: Perennial
  • Growing Zones and range: Zones 2 to 8 depending on the variety
  • Hardiness: Hardy to -20°F (-29°C)
  • Height and width: 2 to 7 feet (.6-2.1m) tall, depending on the variety
  • Foliage: Leaves are sparse, dark green, deeply cut, and spiny toothed.
  • Flowers: Tiny flowers are borne in dense, rounded, conelike umbles with a ruff of stiff, spiny bracts at the base
  • Flower colors: Blue, white
  • Bloom time: Midsummer to frost
  • Uses: Middle of borders; textural effects; dried arrangements
  • Common name: Sea Holly
  • Botanical name: Eryngium spp.
  • Family: Apiaceae
  • Origin: Europe, North Africa

Where to plant Eryngium

  • Grow Eryngium in full sun.
  • Eryngium will grow in poor, dry, and sandy soil. It grows well near the seaside.
  • Eryngium will tolerate heat and drought.

Eryngium uses and companions

  • Use Erynigium in bed and borders; beautiful against a dark background when backlit.
  • Eryngium is a good fresh-cut or dried flower.
  • Good garden companions for Eryngium include Artemisia, Limonium latifolium, Oenothera, Zauschneria.
Sea holly, Eryngium bourgatii
Sea holly, Eryngium bourgatii

When to plant Eryngium

  • Set established Eryngium plants in the garden in spring. Mature sea holly does not like transplanting.
  • Sow seeds in spring.

Planting and spacing Eryngium

  • Space Eryngium 2 feet (.6m) or more apart.
  • Sow seed 1/8 inch deep in containers or evenly prepared soil.

How to water and feed Eryngium

  • Eryngium needs moderate water; established plants are drought tolerant.
  • Fertilizing Eryngium can cause plants to grow tall and flop over.

Eryngium care

  • Eryngium is an excellent cut and dried flower.
  • For drying, pick just before bloom has fully opened and hang them in a warm, dry, dark place.

Eryngium pests and diseases

  • Eryngium is prone to root rot in wet soil especially in winter.
  • Sooty mold is a problem in humid conditions.
Flowers and bracts of sea holly, Eryngium
Flowers and bracts of sea holly, Eryngium

Eryngium propagation

  • Propagate Eryngiumgium by separating small plantlets from the base of the clump.
  • Tap-rooted plants are difficult to divide.
  • Erynigium seed germinates in 12 to 20 days at 68° to 70°F (20°-21°C).
  • Plants self-sow and seedlings are easily moved.

Eryngium varieties to grow

  • Erynigium agavivolium is an evergreen species that grows to 5 feet tall with greenish-white flower heads with spiny bracts.
  • E. alpinum grows to 2 feet tall with deeply cut blue bracts; ‘Blue Star’ is a good variety.
  • A. amethystinum, amethyst sea holly, grows to 2 feet tall bears round, metallic blue flower heads with silver-gray bracts; s cold hardy in Zones 2-8.
  • E. giganteum, giant seas holly is a short-lived perennial that grows to 3 feet tall; bears steel blue flowers,
  • E. pandanifolium, giant sea holly, grows 6 to 7 feet tall and 4’ wide in Zones 8-10.
  • E. planum, flat sea holly is an evergreen species that grows to 3 feet tall and bears pale steely blue flowers surrounded by blue-green bracts.
  • E. yuccifolium bears sword-shaped blue-green leaves and whitish-green flowers; grows to 4 feet tall.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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