Louis Raymond experiments in his own gardens like

a mad scientist, searching out plants that most people have

never seen before & figuring out how to make them perform.- The Boston Globe

…Louis Raymond ensures that trees can grow in Brooklyn…

or just about any other place where concrete consumes

the dirt and skyscrapers shield the sunshine.- USA Today


NEW Trips to Take!

Myrtle's easy when the conditions are right.


NEW Plants to Try!

Louis tries to capture the exact words to describe the fleeting but deep pleasures to be found in these Summer-into-Autumn incredibles.


New Gardening to Do!

Allergic to bees? You can still have an exciting garden, full of flowers and color and wildlife.


Plant Profiles

Salt-water Sea Holly



Such scintillating silver-spidery flowers!  And on a unique water perennial: "Sea-worthy" Sea Holly.  It's the only one of the Sea Hollies to prefer to grow not just near water, but in it—and in brackish water at that.  I'm experimenting with a pot of it standing in a galvanized washtub of fresh water.  (It's a very galvanized-friendly garden here: I must have twenty washtubs in use, let alone a few galvanized horse-troughs.) 


Young plants in bloom their very first season?  So far, so good.  The buds and young flowers are green, but they mature to silver-white.  The largest blossom in the whole candelabra is also the oldest, and therefore the whitest.




Now if only I can overwinter the darned things.  They're native as far north as New Jersey, and my garden's no chillier, but so far (two years and counting) no luck.  See "How to Handle It" for my latest strategies.




To have these subtle constellations of flowers in the garden in August?  Let alone in the water-garden in August?  That's worth plenty of trial and error.



Here's how to grow this uniquely sea-worthy Sea Holly:


Latin Name

Eryngium aquaticum

Common Name

Sea Holly


Apiaceae, the Carrot family.

What kind of plant is it?

Hardy herbaceous perennial.


Zones 6 - 8.


Strongly vertical, both in leaves and flowering stems.

Rate of Growth


Size in ten years

A clump three to foot feet tall and two feet wide.


Spare and see-through.

Grown for

its rarity:  "Sea Holly" is the confusing common name for everything in the diverse Eryngium family.  Although their typical spininess has a holly-like "ouch" factor, they're completely unrelated to the familiar evergreen shrubs and trees.  The "sea" part, though, is sometimes literally appropriate, in that some members are very happy to grow in sun-salt-and-sand locales and even directly along the high-water edge of beaches.  Eryngium aquaticum though, is unique in its preference for growing directly in standing water.  By comparison, all the other "sea" hollies could best be described as beach hollies at best.  E. aquaticum is doubly unique, so to speak, for its amenability to brackish as well as fresh water; few garden-worthy perennials will tolerate anything other than fresh water.


its spidery flowers, pale grey/green/white and held atop tall open clusters. 


its strongly vertical habit, which looks particularly dramatic when a clump can be grown in a large reflecting pool so there's plenty of open water as the ultimate in contrastingly flat "terrain." 

Flowering season

Summer: July and August.


Full sun and, at least when in active growth, never a moment of drought. 

How to handle it

E. aquaticum is at its best when growing in marshy ground or even in shallow water.  (It also handles a "terrestrial" garden life—i.e., being planted in a regular garden bed instead of in a water garden or a marsh—but would be smaller there.)


For the moment, I'm growing mine in a pot that's standing in a galvanized washtub.  I haven't had luck overwintering a pot in my reflecting pool by submerging it more deeply than ice would penetrate.  I also haven't had luck overwintering a pot in my cool and humid basement, where it didn't dry out for a minute.  So this year I'll let the plant get frosted into dormancy, but then store the pot in a saucer of water on the floor of the greenhouse.  Stay tuned.


Assuming your sea holly finds your garden congenial for year-round growing, you may find that dead-heading is important:  Eryngia tend to be self-seeding champs.  But I, for one, would be thrilled to be over-run with E. aquaticum, not least because it's expensive to buy new plants each season.  And, indeed, this year I'll harvest the seed in hopes of getting started on just such a stylish infestation.


If only it were hardier than Zone 6.  If its fussiness about overwintering is any indication, at least as I'm experiencing it, this sea holly might be justifiably scarce in gardens.


Sea hollies are distinctive and (usually) very easy oddities, with enough different species that gardeners from Newfoundland to Santa Monica can (and should) celebrate them.  The really hardy ones—Zone 5 and even lower—are biennials or herbaceous perennials ranging from one to four or five feet tall.  Argentinian Eryngium pandanifolium is a spiny monster to eight feet and higher; it's hardy down only to the warm reaches of Zone 7, and I haven't yet been able to please it in a pot.  All but E. aquaticum thrive if they get excellent drainage and full sun, and are then also not at all fussy about soil. 


Although many of the hardy perennials tout a steel-blue color to the flowers and even the stems of the flower clusters, their show is brief and, unless you grow them in very lean soil, they are notoriously floppy.  Better all around is the Midwest native, E. yuccifolium, with toothy stems like a pineapple top and tall stems of teasel-like green and white flowers.  And best of all, the biennial E. giganteum, with nondescript basal leaves the first year and the next, immense candelabras, to three or four feet, of seriously-spiny silver-white flowers.  Especially with the latter, deadheading is a must; let only one or two flower heads go to seed.  Help reduce self-seeding by cutting candelabra to use, fresh or dried, in bouquets. 




By division in Spring, or by seed.  If E. giganteum is any guide, the seeds need cold as well as sunlight to germinate:  Sow in the Fall atop open ground. 

Native habitat

Eryngium aquaticum is native from New Jersey to Northern Florida.

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