jodi's gotta-have plants: Eryngium, the holly of the sea

Although I haven't said a great deal about this, I signed a contract a few weeks ago to produce a book on great plants for Atlantic Canadian gardeners. Although I had been working on it intermittently for some time prior to signing the contract with my publisher, the work has begun in earnest as the manuscript is due in July. Thus I'm going to be somewhat spotty in blogging in the common weeks and months, and may on occasion offer up some archival articles. For today, however, let me share a bit from a conversation I had the other day with a friend who asked me which perennial I absolutely had to have in my garden. Naturally, I couldn't offer just one, so I rattled off about ten. In the top five, however, or even the top three, is Eryngium, also known as sea-holly.

What’s not to love about eryngiums? They have terrific texture and structure in their leaves, all spiny and bristling with fierceness. They have really cool flowerheads, cones of small flowers in shades of blue, silver, green and amythest, depending on the cultivar and species. And to really accent the flowers, sea hollies have these gorgeous ruffled bracts around the cones. You’ll see them described as looking like the ruffled collar of an Elizabethan costume, and that’s about the most apt description there is.


Sea hollies besotted me before I ever saw one for real—I came across a photo of one in a book on perennials. I think it was E. alpinum, or one of the others with really blue flowers, and I was instantly smitten.



We have a garden that I refer to as the sunset garden, because for much of the season, the colours red, gold, orange and yellow predominate. Daylilies, Asiatic and oriental lilies, rudbeckia, evening primrose, euphorbia ‘Fireglow’, a striking red rose, ‘Robusta’, the big yellow Macrocephala centaurea, and a host of jubilant red lettuce poppies hold court in this garden. What cools it slightly, or perhaps sets it off more, are a few things in cooler colours; Echinacea purpurea, Centaurea montana (purple-blue flowers), C. dealbata (pink flowers), blue lobelia (Lobelia syphilitica), Rosa ‘Souvenir de Philomen Cochet’ (a pristine white rugosa similar to Blanc de Coubert) and a wash of flat sea holly, Eryngium planum.

This faithfully, year after year, produces sprays of flowers, masses of them, shimmering blue, and lasting for a long, long time. They get quite tall, nearly four feet in some spots in the garden, so they make quite a presence. I leave them standing all fall and winter until they are finally worn down, seeds long gone (some back into the garden), and I wait eagerly for the next batch to begin. Occasionally I cut a few stems and bring them indoors to use as dried flowers, and they hold their colour for months on end.

There was a new cultivar released several years ago to great fanfare, E. planum 'Jade Frost.' The excitement with this plant was the variegated leaves, green edged in cream with pink highlights during spring and autumn, and of course the lovely blue flowers. I have one which was given to me last year by a nursery (I don't want to mention the nursery because they appear not to be carrying it this year), and it settled in well, but of course didn't flower. I can't tell if it's survived until the two feet of snow still covering it finally melts away. But I know Nan Ondra had this and had it bloom for her several years ago, so I'm optimistic.

One of the most famous of sea hollies is the delightfully named ‘Miss Willmott’s Ghost.’ Ellen Willmott was a Victorian or Edwardian (born 1858) British gardener with a reputedly eccentric and prickly personality. Her legacy includes a number of plants, but the most famous is Eryngium gigantium; Miss Willmott, in her younger years, would carry seeds of this plant in her pocket, and casually cast them in the gardens of friends and acquaintances. Being of a biennial habit, the plant would germinate and grow quietly, then suddenly in the second year it would erupt into an amazing plant, covered in ghostly silver-green flowers.

I've said this before, on a regular basis, but I'll say it again: If you get a chance to visit The Rock Garden at the Nova Scotia Agricultural College in mid-late summer, go. This marvelous garden includes a splendid expanse of Miss Willmott’s Ghost, which in autumn turns to a handsome tan colour.


One of the more unusual of the sea hollies goes by the equally unusual name of Rattlesnake Master, Eryngium yuccifolium. As you might suspect from the botanical species name, this has yucca-like foliage, and it puts up stalks a good five feet tall, festooned at the top with greenish grey cones (they're actually umbels, but you get the point). It's a native of the tallgrass prairies, and I saw it growing in its native environment in Missouri two years ago, but it also does fine in a well-drained location in my front garden. It's come back reliably for three years, but hasn't spread unduly. Not that I'd worry about seedlings of any member of this genus.



At a talk one day, I encountered an audience member who told me, with a sour expression, that sea holly was NOT a favourite of hers because it produced seedlings and kept increasing in numbers. I was about to suggest that she just mulch quite well around hers to reduce germination, when several other members of the audience offered to come relieve her of those dratted seedlings. Problem solved. You need to dig seedlings of Eryngium early in the season, however, careful not to break too much of their tap roots, and allow them to sulk for a year to recover. There could, however, never be too many eryngiums in my garden, as they make me intensely happy.

They also make my friends the bees intensely happy—all the sea hollies are regularly awash in bees, bumble and honey, and bee-mimics too. Talk about a ‘bee-loud glade!’ Well, not a glade, perhaps, but Yeats would no doubt appreciate the song of bees in our garden.