Sea hollies (Eryngium) have spiky leaves and thistle-like flowers in colours ranging from grey to intense cobalt blue, surrounded by a characteristic ‘ruff’. They make striking garden plants and have excellent wildlife value, particularly for pollinators. There are over 250 species of Eryngium, including plenty of cultivated varieties. As their name suggests, they grow well in coastal areas. They look wonderful in gravel gardens or mixed herbaceous borders.
Eryngiums make good winter silhouettes in the garden and the flowerheads work well in both fresh and dried arrangements. To dry sea holly flowers, simply cut them at the base of the plant and hang them upside down in a dry spot such as a shed or a garage.
How to grow sea hollyGrow sea hollies in full sun in free-draining soil, ideally where the soil stays relatively dry in winter. Protect the roots with a straw mulch in winter. Cut back the flower spikes in spring.
Where to grow eryngiumsEryngiums need plenty of sunshine and free-draining soil. They can tolerate poor soil, and a spot at the foot of a wall is a good position as the soil will remain dry over winter. It’s also a good idea to plant eryngiums away from the edge of a border or path, as their spikes can be quite sharp. They work well in gravel gardens and don’t need a lot of watering.
How to plant eryngiumsDig a generous hole, larger than the pot your sea holly came in and add a handful of grit to boost drainage. Follow our step by step guide to planting perennials.
Caring for eryngiumsIn colder climates you may need to protect the roots with a mulch of straw over winter, and tidy spent foliage in spring to prevent rot.
Propagating eryngiumsSpecies eryngiums can be grown from seed, although if you have
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