They have a long history in Europe, and they are also Texas wildflowers. They go by two odd-sounding names — eryngium and eryngo. Yet, these eye-catching plants are not well known in America, where their garden value is commonly overlooked.

Perceptual errors have contributed to this oversight. When spotted in the wild, some eryngos are often mistaken for thistles. Others are sometimes misperceived as yuccas. And hearing the entire group of more than 230 eryngium species referred to as “sea holly” doesn’t seem to clarify anything.

Long ago, though, eryngium was much better known in America, and there is good reason for today’s gardeners to become reacquainted with it.

YUCCA-LEAF SNAKEROOT
In early America, yucca-leaf snakeroot (E. yuccifolium), also known as bristle-leaf eryngo and rattlesnake master, was prized for its medicinal properties. As Matt Turner has recently reported in Remarkable Plants of Texas, the tuberous root of this widespread plant was used by Native Americans for various therapeutic and ceremonial purposes. It was generally applied as an antidote for poisoning, especially snakebite. “Many American tribes were aware of this precise use, across thousands of miles,” Turner found, just as “in the Old World, the Romans utilized the root of another species of Eryngium for exactly the same purpose.”

In the Midwest and Southwest, some nineteenth-century settlers learned about the medicinal reputation of this plant from Native Americans. “It could be consumed raw, steeped in water as an infusion, boiled as a decoction, or chewed to make a poultice for external application,” Turner learned. One 1840s report from Texas, according to Turner, mentioned that the root tastes like a “strong bitter carrot.” This isn’t surprising because eryngium belongs to the parsley or carrot family (Apiaceae), which includes poison hemlock (Conium maculatum), Queen Anne’s lace (Daucus carota) and wild dill (Polytaenia nuttallii).

A tall-grass prairie plant often mistaken for a yucca, bristle-leaf eryngo can bloom as early as May and is marketed today as a drought-tolerant garden perennial capable of thriving in sandy or clayey soils. In Texas, wild yucca-leaf snakeroot tends to parade clusters of greenish-white flower ‘globes’ on spikes high above the foliage.

But there are variations on that architectural theme. Tony Avent, owner of Plant Delights Nursery in North Carolina, has described the powder-blue leaves of his ‘Kershaw Blue’ cultivar of E. yuccifolium as “certainly the most dramatic I’d ever seen on this species, topped with 30-inch tall flower spikes of tan, alien-like flowers in late summer.”

LEAVENWORTH’S ERYNGO
Leavenworth’s eryngo (E. leavenworthii) ranges from Far West Texas, over the Edwards Plateau and throughout both South and North Central Texas. During late summer and early autumn, this beautiful prickly annual, often misperceived as a thistle, has been featured in model native-plant beds at the Ladybird Johnson Wildflower Center in Austin.

This plant’s tiny flowers, with thrust-out blue anthers, are conically clustered and augmented by spiny, brightly hued bracts (modified leaves). Most of the entire plant is purple, and it will hold this intense color for many months if its 1-to-4 foot stems are cut cleanly just after their flowers have opened and then are dried upside down.

MEXICAN THISTLE
For a lighter hue and brighter effect, the Trans-Pecos native E. heterophyllum looks like a silvery thistle. As this perennial matures, its autumnal flower clusters change to sky blue.

The showy bracts of Mexican thistle are smaller than those of Leavenworth’s eryngo, but they make no less an impression. And, as cut flowers, they keep their form in arrangements just as well as E. leavenworthii.

PLAINS ERYNGO
A number of outstanding garden cultivars, including steely ‘Blue Glitter’ and silvery ‘Blue Hobbit,’ have been derived from the plains eryngo (E. planum). ‘Blue Hobbit,’ which prefers draining fertile soil, grows to about a foot high. ‘Blue Glitter,’ which prefers sandy soil, reaches about 2 feet. Both are sun-perennials designed to endure heat and drought.

‘Jade Frost’ is a variegated plains eryngo selection. In spring, the new leaves of this 7-inch perennial are fringed by pink, which turns to white during summer.

But the plains eryngo benefits from winters typical of Colorado, South Dakota, Wisconsin and Michigan — states where this naturalized European native grows wild. So using its cultivars as in-ground plants in Texas amounts to a reasonable experiment, particularly in the northern half of our state.

Fortunately, clumping plains eryngo cultivars also make great deep-container selections. Whether in-ground or potted, eryngium’s unusual architectural form is particularly striking when companioned with compact daylilies (such as ‘Stella d’Oro’), coneflowers (such as ‘Green Jewel’) or a short ornamental grass.

OTHER SEA HOLLIES
Alpine sea holly (E. alpinum) also qualifies for both the cold-hardiness and heat zones of most of Texas, but its cultivars might perform best in container-controlled conditions. Although this perennial, like other ornamental eryngos, is often called sea holly, the popular name actually refers to only a few eryngium species, particularly holly-leafed E. maritimum found along European and eastern U.S. seacoasts.

The Alpine eryngo selection ‘Superbum,’ as its name suggests, is touted for its hardiness. Standing at 2 feet, this taprooted perennial thrives in alkaline soils and displays blue thistle-like flower heads surrounded by soft spines. It’s a good candidate for rock gardens.

Dr. Allan Armitage, horticulture professor at the University of Georgia, has raved about the “marvelous ornamental value” of ‘Blue Star,’ another Alpine eryngium cultivar. “One of the bluest of the sea hollies,” Armitage reported, its “flower head is oblong like a pineapple” and “looks like exploding fireworks.”

‘Big Blue,’ with electric-hued, 4-inch wide blooms, is usually identified as Eryngium x zabelii, which means it’s a hybrid cross between E. alpinum and E. bourgatii (a Spanish eryngo). Nearly iridescent, ‘Big Blue’ is aptly described by its marketer, Blooms of Bressingham, as “a bold garden accent — a tremendous garden presence, impossible to overlook.”

Sun-loving ‘Sapphire Blue,’ another hybrid, features somewhat shorter and smaller flowers ringed by a narrow band of spiny, blue-green bracts. It thrives in poor sandy soils and will, apparently, tend to sprawl if planted in richer dirt. Unlike plains eryngo in the wild, ‘Sapphire Blue’ produces sterile seed and so cannot spread.

OVERVIEW
Eryngos vary in their requirements, and so a little homework is advised before cultivating any of them. For example, ornamental eryngiums tend to be perennials, but Leavenworth’s eryngo is an annual. As we also have observed, ornamental eryngiums tend to prefer dry, well-drained, sandy soil, but ‘Blue Hobbit’ prefers well-drained fertile soil.

There are, however, two eryngo rules which do not vary. One is that the intensity of an eryngium’s color increases in proportion to its exposure to sunlight. The other rule is that over time eryngos with taproots go deep. That’s both good and bad. Deep taproots enable these plants to withstand heat and drought, but they also make their transplantation nearly impossible and usually fatal. So plan carefully in advance, for light and design, before planting any tuberous eryngium.

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