Also known as
Blue Eryngo, Flat-Leaved Eryngo, Kok-Bas, Plains Eryngo, Cross Thistle, Flat Eryngo, Flat Rattlesnake Master, Plains Coyote-Thistle
Flat Sea Holly (Eryngium planum) (14240745500) by Bernard DUPONT (CC BY-SA 2.0)
2 years to reach maturity
This plant has no fragrance
More images of Sea Holly
Sea Holly Overview
Eryngium planum is a striking herbaceous perennial plant. It is used to create decorative borders, beds, pot plants, containers and landscapes. Excellent for cut or dried flower arrangements. The blue colour intensifies with cold weather. Be aware, they can overgrow and invade areas quickly, and with every little root that stays behind in the soil growing into a new plant, they are tricky to remove from an area! This species is part of the Royal Horticultural Society “Plants for Pollinators” initiative to showcase plants that support pollinator populations by providing ample amounts of nectar and/ or pollen. A great choice for encouraging pollinating insect wildlife into your garden!
Common problems with Sea Holly
Root rot (needs dry or well-draining soils). Leaf spot diseases. Aphids, slugs and snails.
How to harvest Sea Holly
Harvest flowers when the entire flower heads and bracts turn blue.
How to propagate Sea Holly
Propagate seeds in containers in a cold frame as soon as ripe and mature.
Propagate by division during spring, although they may be slow to re-establish.
Insert root cuttings in late winter directly in the soil.
Special features of Sea Holly
Attracts useful insects
Butterflies and beetles love the flowers.
Grows well in pots, beds and containers in well-drained sandy soil under direct light.
The fleshy roots help the plant to be drought tolerance.
Grows well in pots, beds and containers in well-drained sandy soil.
Other uses of Sea Holly
Borders This plant has been given an OPALS rating of 4 and can be used sparingly in a low allergen planting scheme.
The plant is diuretic. It is also used in the treatment of whooping cough.
The roots are used for medicinal purposes. Taste is sweetish and mucilaginous, but the root has no odour.