In common with yesterday’s post, this one is inspired by finding some images in my photo library when looking for something else. Erygiums are commonly called sea hollies, after the species that is native to Northern Europe. In gardens they are represented by other species. The most common are E. planum, with rounded basal leaves and wiry, much-branched stems with silvery blue flowers, E. giganteum, a biennial with soft, rounded basal leaves and very spiky silvery flowers and E. alpinum with very frilly bracts around the flowers. All the European species have colourful flowers and are rarely grown for their foliage. In contrast, the South American species have a very different look, with rosettes of narrow leaves, often armed with spines, and tall stems of rather dull flowers with less attractive bracts surrounding the blooms.

Sea holly at Great Yarmouth with Scroby Sands offshore wind farm in the distance

Eryngiums are in the Apiaceae, relatives of carrots and fennel, with umbels of flowers – all arising from one point, like the spokes of an umbrella, though there can be umbels of umbels!

Most of these plants are quite easy to grow, though all demand full sun and a well-drained soil.

The flowers of the European species are small, crowded in domed heads and surrounded by thick, long-lasting bracts that are usually silvery or blue. This structure is reminiscent of the Asteraceae, the bracts doing all the attraction, for a prolonged period as the flowers open in succession, like a daisy or sunflower where the ray florets stay looking good all the time the central, fertile florets open.

A well-coloured sea holly at Southport

Eryngium maritimum is the true sea holly and has these colourful and attractive flowers but the leaves are spiny too. The whole plant is prickly, tough and completely unbrowsable. Seeing it in its natural habitat, as with any plant, helps us understand its needs. These photos show it in two places, at Southport in the Northwest of England and at Great Yarmouth on the east coast – almost as east as you can get in England. In both cases it is growing in pure sand, in dunes. You can see that the thick roots help to bind the dunes but, if the sand blows away or is otherwise eroded, the roots are exposed. Eryngiums are one of the easiest plants to grow from root cuttings and you can see why here – if the roots are exposed and the plant snaps off the roots, it is a big advantage if the roots can sprout new plants.

Sea holly at Southport struggling against erosion of the dune

It also shows just how succulent the plants are and how they must hate wet, heavy soils. This specific habitat explains why the native sea holly is so rarely seen in gardens. Most eryngiums have leaves that are very un-holly like but this species explains the common name well.

And in case you want to know where Southport is, it is the southern and more grown up cousin of Blackpool where Strictly is taking place this weekend. If you don’t understand that, it is too complicated to explain.

eryngium maritimum, eryngium maritimum in the wild