Blue Sea Holly – How to Sow, Grow and Enjoy 5 of the Best Eryngium for Full-Sun Gardens.

Blue Sea Holly – How to Sow, Grow and Enjoy 5 of the Best Eryngium for Full-Sun Gardens.

Blue Sea Holly is a striking, architectural, often silverized annual or short-lived perennial thistle you will want to grow from seed. Often seed in designer gardens, blue sea holly brings a bold dramatic effect to any garden.

Best started from seed sown in Fall, Eryngium, often referred to as blue sea holly is a genus with over 200 hundred species with wide distribution globally, a large number of which are found native in Central America.

5 of the best Eryngium to grow from seed favor dry, free-draining, full-sun locations. Once germinated the plant prefers to grow undisturbed and is best sown from seed sown directly where they are to flower.


Bees are attracted to the nectar of sea holly and despite the thistle appearance, butterflies and pollinators are regular visitors to this rosette-forming, spiny perennial umbel. Be warned the pollinators can navigate the spines, pets should avoid touching the spines and gardeners should wear thick gloves when clean-up in the spring necessary.


    Sea Holly from Seed

    Pollinator Perennials
  • Blue Sea Holly


    Blue Sea Holly Seeds

How I Grow Eryngium:

I have had the best results when sowing Eryngium direct in Fall or simply allowing the parent plant to set seed and leaving the seeds to naturally scarify and subsequently germinate.


Note: Two months of cold stratification or direct sowing or winter dormancy is required!


Direct sow seeds in fall and allow seeds to naturally cold stratify, this way they will germinate in Spring as temperatures improve. Leave undisturbed where they are to flower.


Place Eryngium SEEDS in a zipper bag or cover pots/trays with black plastic after watering and seal with a rubber band then cold stratify in the fridge for 60 days. 

Keep soil moist, not wet. At the end of the cold stratification, remove black plastic from pots and place trays in a warm, sunny location. 


When starting seeds indoors, sow finely and gently press seeds to make contact with soil as light is required for germination. 

Start in trays or small pots on a window sill or glasshouse several weeks before the last frost in your area.


Seeds started indoors will need acclimatizing to outdoor tempertures, this should be done gradulay by placing young plants in a shady location outdoors during the warmer part of the day, slowly increase the time to harden plants to spring tempertures.

Planting out:

Re-locating self-sown seeds of blue sea holly should be attempted as the seedling produces its true leaves a few weeks after germinating, this way you are unlikely to damage the delicate taproot. 

Planting out seedlings that have been grown indoors, should be carried out with care, watering the pots or trays well prior to transferring from pots will minimize root disturbance. 

Grow with:

Native Echinacea, Geum, Achillea, Rudbeckia, Oenothera, and Monarda these 6 perennials provide additional seasonal interest, and as the sea holly is long flowering, dry well and can be left standing through winter allowing a fifth season to be enjoyed by wildlife and winters brave garden visitors.

If purchasing seeds in Spring then chill for a few weeks in the vegetable draw of the refrigerator prior to sowing where they are to flower.

5 Best Eryngium:

There are several notable species and cultivars of sea holly that are worthy of a place in your pollinator garden.

E. alpinum – heart shaped leaves and the bluest of flower bracts.

E. bourgatti – metallic blue bracts and flower stems.

Eryngium zabelli “Big Blue” – a cultivar resulting from a cross between species E. alpinum and E. bourgatti.

E. planum – silver blue flower stems often used as a cut flower.

E. yuccifolium – great for naturilizing may need to be kept in check and some seedlings removed as ongoing maintenance.

Plant Magick:

If Love, harmony, and marital bliss are in order then Eryngium is the plant for you, growing sea holly around the garden will help bring peace. Try burning the dried flower stems as incense or use in a love spell to help to re-ignite passion.

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