Sea Hollies by Martin Blow

June and July is the time Eryngiums (Sea Hollies) are coming into bloom but they’ve been looking good all spring with their dramatic, exotic looking leaves and will continue to inspire into the autumn as architectural seed heads replace the flowers.

The largest specimen in our garden is Eryngium eburneum (the ivory white sea holly), now over 4ft / 120cm across and sending up multiple branching stems topped with whitish thimble flowers to a height of 4-5ft / 120-150cm.

Like a lot of ornamental sea hollies this plant originates from South America, but we’ve found it to be completely hardy in our free draining soil. It is usually evergreen and holds its seed heads through the winter. Like many species the leaves are tooth-edged with added spines requiring stout gloves when removing dead leaves and old flower stems at the end of winter.

It is possible to divide the plant and to take root cuttings, but seed is the preferred method. We found that seed heads are best left on the plant and then collected in February and sown in early March and placed outdoors. Germination takes 8 weeks or so. This method of seed sowing applies to all types although germination takes a lot longer with some species – up to 2 years for Miss Wilmott’s Ghost (E. giganteum) so don’t give up on them!

Eryngium agavifolium is in a similar vein to this plant but with wider, tooth-edged leaves and greenish flowers. Looking like a desert agave, it is completely hardy and appreciates a deep, rich but draining soil. In the wild it grows in bogs but wouldn’t take the winter wet here.

Eryngium zabelii Jewel, an old variety with intensely blue flower stems and flowers – most of the flower colour comes from the stiff, spikey bracts that surround the flowers. This one is deciduous leaving just brown flower stems behind when the leaves die in winter.

Like all eryngiums it will survive drought, but this type shows its suffering with browning leaves that are best removed. Jewel is about 2ft 6in / 75cm tall.

Slightly taller, with equally blue stems but less dramatic bracts, is Eryngium planum, which now graces our blue and yellow border.

There are lots of new varieties of these two species, all much of a muchness, and often a triumph of marketing over advances in breeding.

Smaller is Eryngium bourgatii with the whole plant giving a bluish silver effect from the silver lines on the leaves to the silver-blue flowers. A good choice for the front of the border, rockery or gravel garden.

A quick word about Miss Wilmott’s Ghost – E. giganteum. This is biennial so if you lose it after flowering that’s what’s meant to be! Its name comes from the habit of the eponymous lady to sprinkle a little of its seed in gardens she visited when she felt they needed brightening up!

Janet & I organise Plant Hunters’ Fairs, specialist plant fairs at wonderful locations. Middleton Hall, Nr Tamworth, B78 2AE on Sunday 26th June and Sunday 21st August, entry to Gardens & Plant Fair only £3 (special reduced entry price), ticket required, please see website. 1620’s House and Garden, Nr Coalville, LE67 2FW on Sunday 31st July, entry to Garden & Plant Fair £1, ticket required, please see website. For a full list of all 30 of our 2022 plant fairs please visit Please check website for ticketing information and all the latest updates before travelling.