When planning your flower garden, wouldn't it be nice to have something rare and unusual to show off to your neighbors? You can do just that if you plant Sea Holly flowers, as you can see from the photographs. Some of them are the rarest color available—blue—and once you plant them, they are so easy to maintain, requiring very little care. The Big Blue Sea Holly (Eryngium zabelii) is my personal favorite with its steel blue prickly flowers laying atop a beautiful mound of silvery blue leaves.
But, when it comes to Sea Holly, the initial planning is very important because they have tap roots that, although they can grow deep into the ground and find water where other plants can't, don't like to be disturbed once planted. Wherever you plant them, that's where they need to stay. Kathy Wolfe of the Washington State University Extension Service wrote a great paper on roots called The Hidden World of Roots.
Sea Holly plants love sunshine and normal or sandy soil and, once established, they are extremely drought resistant.* Keep in mind that they will grow to almost three feet high and have a spread of about 24 inches, so plant them where they will have adequate room and access to plenty of sunshine.
You will need to cut back the old stems to ground level, preferably in late fall (although you could wait until early spring, which won't be too late should you forget in the fall). They should come back with a vengeance, then provide you with bright blooms all summer long.
Note: In long periods of drought, however, you will still want to make sure they get adequate water.
Most nurseries should have several different species of Eryngium, which have been cultivated as garden plants; and most of the sea holly species are considered as perennials in USDA Hardiness Zones 4 - 9. This is a brief overview of some of the most common ones you might find available, listing both the common name and the botanical name:
Question: my Eryngium is supposed to be zabelli, but it has green leaves, so is it?
Answer: It could be, as zabelli tends to have more green than other varieties. If the center part is completely green as well, it probably is zabelli.
© 2017 Mike and Dorothy McKenney
Mike and Dorothy McKenney (author) from United States on August 06, 2018:
Paul, can you tell me what type of sea holly you planted. Some of them are naturally grey-green color, although I wasn't aware of them turning blue, and then turning back to the original color. Let me know and I'll do some serious research. Thanks!
PaulBrennan on August 05, 2018:
I planted a sea holly in the front garden (with lots of compost into a clay soil and lots of sun). After a few days, and as expected, the flowers and petals turned from grey-green to a beautiful shiny blue. Now, a few weeks later the blue colour has disappeared and it's back to the original grey-green...Any ideas as t what's happening???
Mike and Dorothy McKenney (author) from United States on June 25, 2017:
Intriguing is a good word for these, indeed. Thanks for stopping by.
Emily Lantry from Tennessee on June 25, 2017:
I've never heard of this plant, but I am so intrigued! I really want to find some. Thank you so much for sharing!
Mike and Dorothy McKenney (author) from United States on June 20, 2017:
Thanks Dolores. I'm glad you've had success moving them; your thumb must be greener than mine...lol.
Dolores Monet from East Coast, United States on June 20, 2017:
Beautiful pictures! I have 2 sea hollies in my garden. I love the luminous blue/green hue. But now that shade is taking over, I worry that they will become unhappy. I have moved sea holly before as well as other plants people say you can't move. I wait until the plant is dormant in winter and dig them up with a large clump of the surrounding soil. I dig deep as well. This has worked for several plants.