How to Grow Eryngium — Sea Holly

Eryngium Sea holly

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.

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