Discover sea holly!
Sea holly’s prickly starburst blooms in shades of blue to gray always get a second look, but there’s more to love about this unique perennial than meets the eye. It’s drought- and salt-tolerant with plenty of flowers to cut for bouquets fresh or dried, and insect pollinators love it! This big group of plants is native mostly in mountainous and coastal regions worldwide, but only a few species and hybrids are for sale in garden centers, where you may also find sea holly’s North American cousin, rattlesnake master (Eryngium yuccafolium), which has similar structural blooms but without the spiny bracts and long strappy foliage.
Sea holly comes in a variety of colors and sizes
The tiny true flowers are tucked into thistlelike center cones surrounded by stiff bracts that can be long or short, deeply cut or broad. Most are blue or silver-blue, such as ‘Sapphire Blue’ above that really pops against the gold-foliaged Japanese spirea (Spiraea japonica). Leaves can be maple-like, rounded or oval with a leathery texture that helps conserve water. And they range in size from 12-inch-tall ‘Blue Hobbit’ flat sea holly (Eryngium planum) to Miss Willmott’s ghost (E. giganteum) that can reach 6 feet in ideal growing conditions.
Head-turning sea holly flowers
There’s nothing quite like sea holly’s flower shape, so wherever you grow it, this perennial steals the show. The spiny 4-inch blooms of 'Big Blue' above seem to burst through a pink cloud of queen of the prairie (Filipendula rubra) and red bee balm (Monarda didyma), saying “Look at me!” Its well-defined shape adds structure to the grouping so softer flower shapes don’t all merge together.
Try silver blooms
And if you like to sit on the patio after the sun sets, silver flowers and foliage can add a shimmer to the garden at night. Silvery-white Miss Willmott’s ghost, with its larger size and broader bracts, makes an excellent addition to a moon garden.
You Might Also Like:
How to Grow Bee Balm
Watch Our Talk & Tour Garden Videos on YouTube
Drought-Tolerant Walkway Garden Plan
How to grow sea holly
For healthy plants with lots of blooms, grow sea holly in full sun and well-drained soil. Too much shade and you’ll have fewer stems that will be long and leggy. Where nights are cool (around 55 degrees F) the blue color is more intense. Sea holly thrives in most soil types as long as it’s well drained. No need for regular feeding— this perennial prefers a leaner diet.
Shopping for sea holly plants
Buying potted plants at the garden center or from online nurseries is the surest way to get the species or variety of sea holly that you want. You’ll also sometimes find bags of bare root plants in big-box stores. I snagged a few one spring because it was an economical way to get a grouping of plants. The bags had three roots each. Although a couple had rotted, I started the rest in gallon-sized nursery pots filled with potting mix and set them on my deck after the threat of frost had passed. Within a few weeks the foliage had reached the edge of the nursery pot, and the plants looked vigorous enough to go into the garden.
Sea holly sources
- Digging Dog, 707-937-1235
- Sooner Plant Farm, 918-453-0771
Starting sea holly from seed can be a challenge
You can start sea holly from seed, but even if it’s fresh, the germination rate is usually only around 50 percent. If you want to try it anyway, sow seed in the ground outdoors in early spring or in fall up to 2 months before the first frost for your area. Alternately, start them indoors 6 to 8 weeks before your average last frost date. Either way they need light to germinate, so don’t cover the seeds with potting mix or soil. Keep the flats in a spot that stays 65 to 75 degrees F to encourage germination.
How to get more sea holly plants
Most sea hollies have a taproot, so division is challenging. Miss Willmott’s ghost will reseed and you can easily move young seedlings during the first season. In addition, keep an eye out for plantlets that form at the base of mature specimens and slice them from the mother plant with a soil knife. As long as the new piece has some roots and a few leaves, it will grow just fine. Replant each new piece at the same level it was growing, to avoid rot. Wear gloves when you’re deadheading or dividing and especially when you’re cleaning up in spring — dried-out leaves are even pricklier than fresh ones.
How to care for sea holly plants
You can deadhead sea holly if you want to prevent reseeding, or leave them to dry in place. Of course you’ll also want to snip a few of those amazing blooms for bouquets.
Jennifer O’Neal, co-owner of PepperHarrow cut flower farm in Iowa, loves sea holly and grows several varieties to use in arrangements fresh and dried. She finds that Miss Willmott’s ghost, ‘Big Blue’ and alpine sea holly’s (Eryngium alpinum) big flowers make great additions to summer bouquets. But ‘Blue Hobbit’ is daintier and easier to work into small, dried arrangements, such as flower crowns. Find these and other sea holly varieties you’ll want to try in the gallery below.
Try sea holly in dried floral arrangements
While Jennifer has had cut sea holly blooms last for up to 3 weeks in a vase, she also dries them. To do this she secures up to five stems together in a rubber band (too many might get moldy), then hangs the bunch in a dry spot out of direct sunlight so the color won’t fade. In a few weeks, the flowers are ready for dry arrangements to enjoy even when the garden is done for the season.
You Might Also Like:
Best Flowers to Dry
DIY Dried Floral Wreath
Garden Projects Playlist on YouTube
Meet different types of sea holly
Check out the gallery below to meet a few interesting sea holly varieties to try in your garden.
