Eryngium Alpinum Seeds

Eryngium alpinum, commonly known as Alpine Sea Holly, is a dramatic perennial grown for its metallic blue flower heads and spiny, silvery bracts.

 

Its architectural form and thistle-like texture add bold contrast to borders, gravel gardens, and floral arrangements. ‘Blue Star’ is a standout cultivar, producing vivid blue blooms on upright stems that attract bees and butterflies throughout summer.

 

Seed Qty Approx 0.3 grams

 

Botanical name: Eryngium alpinum

Common name: Alpine Sea Holly

Height: 60–90 cm

Spacing: 30–40 cm

Position: Full sun

Soil: Dry, sandy, well-drained; tolerates saline conditions

Sow depth: Surface sow (light required for germination)

Sow spacing: Thinly in trays or modules

Row spacing: Not applicable

When to sow (indoors): January to March or September to October

When to sow (outdoors): Not recommended

Germination time: 7–21 days at 22–24°C

When to transplant: 5–8 weeks after emergence

Time to flowering: Flowers in second year

Suitable for containers: Yes, with deep pots

Hardiness: Hardy perennial (Zones 3–8)

Pollinator-friendly: Yes

Edible: No

 

Sowing guide

 

Sow seeds on the surface of moist compost and press lightly without covering. Maintain warmth and humidity until germination. Transplant into cell trays or pots once seedlings are large enough to handle. Harden off and plant out after the last frost. Eryngium dislikes root disturbance, so transplant carefully.

 

Growing notes

 

Grow in full sun with excellent drainage. Avoid overwatering, especially in heavy soils. Once established, plants are drought-tolerant and long-lived. Cut flower stems when bracts are fully coloured for fresh or dried use. Clumps spread slowly and can remain undisturbed for years.

 

Why we love it

 

‘Blue Star’ brings bold texture and metallic colour to summer borders. Its spiky silhouette pairs beautifully with grasses, echinacea, and rudbeckia. A magnet for pollinators and a favourite for dried arrangements, it’s both sculptural and ecologically valuable.

 

 

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