Eryngium (Sea Holly)

Eryngium planum Sea Holly / Flat Sea Holly

Steel-blue spiky thistle-like flowers above architectural silvery-blue stems and basal foliage — Sea Holly is the structural perennial that brings unmistakable seaside character, prairie-grade drought tolerance, and an entire summer of dramatic blue colour to any sunny well-drained position.

Sea Holly genuinely earns the "holly" in its name. The flower heads are cones of densely-packed tiny florets surrounded by a striking ruff of spiky, holly-like bracts in saturated metallic steel-blue — far more architectural than ornamental, the whole plant reading as a piece of natural sculpture. Above silvery-blue branching stems and a basal rosette of mid-green leathery leaves, the flowers appear from June through August, with the structural bracts persisting into autumn long after the central florets have finished. Hardy perennial (H7), surviving harsh UK winters with ease. Drought-tolerant in the extreme — Eryngium is one of the most reliable plants for sun-baked positions where almost nothing else will grow. RHS Plants for Pollinators recognised, particularly valued by bees and a wide range of beneficial insects. Height 70–90cm.

A note on growing

Eryngium has a long taproot and resents transplanting — direct sowing where plants are to grow is the most reliable method. Direct sow outdoors from March to June. Cover with about 5mm of soil. Germination is slow and erratic — typically 14–30 days, sometimes longer; do not give up early. A pre-sowing cold treatment (a few weeks in the fridge before sowing) can improve germination significantly. Indoor-sown seedlings should be moved into deep individual pots and planted out before the taproot reaches the bottom.

Plant out into full sun in poor, dry, well-drained soil. Eryngium genuinely prefers lean, sandy, gravelly conditions and resents rich or moisture-retentive ground (where it tends to flop and lose its characteristic compact form). Coastal gardens are ideal — Sea Holly is naturally adapted to salt-laden coastal conditions. Once established, drought tolerance is essentially complete. Like most taproot-perennials from seed, expect Year 1 establishment with modest flowering and Year 2+ for the full architectural display.

⚠️ Spiky: the bracts are genuinely sharp. Wear gardening gloves when cutting or working around mature plants.

Where it shines

In coastal gardens, where the natural salt tolerance and visual association make Sea Holly entirely at home. In gravel and Mediterranean-style gardens, where the drought-tolerance and architectural form suit the conditions perfectly. In modern, sculptural cottage planting where the metallic blue and spiky outlines provide proper textural contrast against rounded or softer companions. As a cut flower for modern, structural arrangements — exceptional vase life. As a dried flower — the metallic blue holds particularly well, and the spiky bracts maintain their shape for years. We particularly value Eryngium in our dried flower range here at Salle Moor Hall Farm.

Plant alongside

For a sun-baked dry-garden combination, pair Eryngium with Echinops ritro (matching blue but different shape — spheres against spikes, both architectural), Echinacea (flat pink discs adding colour and softness), and grasses for movement. For dried flower harvesting, combine with Bunny Tails, Bupleurum 'Griffithii' and Statice. For coastal gardens, plant alongside Lavender (if stocked) and silver-leaved companions.

Delivery

The seeds will be dispatched direct to you by Bishy Barnabees. Please allow up to 5 days for delivery.

Delivery:

Delivery to mainland UK is calculated at checkout. For all other areas and large orders please ask for a quote. Orders will be sent by express next day delivery (DPD). They will be dispatched on a next working day service, with the exception of Ireland where it may take two days. Please allow up to 48 hours for delivery in the UK as the couriers may have already been and collected on the day you send your order in. Smaller orders for pouches, pockets, bags and pots may be sent via Royal Mail delivery. Please ensure you supply an email address and a mobile so you can be updated about your delivery. Should you have any problems with your delivery, please contact us at sales@naturalgrower.co.uk.

Special Deliveries

Saturday or weekday morning deliveries can be arranged, but there will be a surcharge. Please contact us to request a price for either of these delivery services. If you need a parcel sending outside of the UK, please contact us for a quote.

Returns:

If you are not completely happy with any product that you have ordered from us, you may return it to us in its original condition any time within 14 calendar days from the date of dispatch. Products must be returned in their original condition. Please contact us at sales@naturalgrower.co.uk to arrange a return. If you return a product by post, you will need to pay the costs of returning the product to us and obtain proof of posting.