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Michigan Gardener | June 2016 | MichiganGardener.com
Quick reference to Eryngium species
Eric Hofley / Michigan Gardener
Miss Willmottâs ghost (E. giganteum) is a striking, architectural plant, with flower stalks that can reach up to five feet tall.
Alpine sea holly (E. alpinum) â One of the most ornamental, with a feathery ruff of silver-blue bracts beneath a large, cone-like center. A European alpine species, it may be temperamental in the hot, humid Midwest. Needs good drainage. 1-2 feet tall. Amethyst sea holly (E. amethystinum) â The hardiest species, to zone 2. Clusters of small, steely blue flowers with sharp bracts. 1-2 feet tall. Mediterranean sea holly (E. bourgatii) Large, blue, pineapple-shaped flowers with prominent bracts. Grayish foliage with showy white veins. 1-2 feet tall. Giant sea holly (E. giganteum) â Known as âMiss Willmottâs ghost.â Prominent gray-green cone, surrounded by pointed silver bracts. Biennial. Up to 5 feet tall. Flat sea holly (E. planum) â One of the easiest to grow, not fussy about soil. Will tolerate heavier soils. The seed-grown variety âBlue Glitterâ was originally developed for the cut flower market, but also makes an excellent garden perennial. 3-4 feet tall. Marble-leaf sea holly (E. variifolium) Dark green, glossy foliage, heavily veined white. The spiny flowers, borne in dense clusters, are gray-blue with very sharp, silvery white bracts. 12-16 inches tall. Rattlesnake master (E. yuccifolium) Native to central and eastern U.S. Yucca-like, gray-green foliage. Branched flower stems bear prickly, silvery white, ball-like flowers. Easy from seed. 3-5 feet tall. Big Blue sea holly (E. x zabelii, a hybrid of E. alpinum and E. bourgatii) â The Blooms of Bressingham cultivar âBig Blueâ has 4-inch, electric blue flowers on steel blue stems. Hardy to zone 4, possibly colder. 2-3 feet tall.
Eric Hofley / Michigan Gardener
Mediterranean sea holly (E. bourgatii) has large blue flowers with prominent bracts. The grayish foliage includes showy white veins. continued from page 38 Blooms of Bressingham; a hybrid of E. alpinum and E. bourgatii) canât be reproduced from seed, but are now accessible and affordable due to tissue culture propagation.
Native eryngium Rattlesnake master (E. yuccifolium) is a very different-looking member of this genus. As the name suggests, its foliage resembles that of yucca, although less upright. The gray-green, blade-like leaves form clumps from which tall, branched stems arise, bearing many white
Blooms of Bressingham
Eric Hofley / Michigan Gardener
The sea holly âBig Blueâ has 4-inch, electric blue flowers on steely blue stems.
Sea holly blue is a true blue. In some species, even the stems carrying the flowers are blue.
clover-like heads. Although not at all similar in appearance to the blue and silver European species, it also provides a dramatic effect in the garden. This is one of the few North American eryngiums with ornamental qualities. It is native to most of the eastern United States, from Minnesota south to Texas, and from Nebraska east to Maryland. Unlike the European species, which demand excellent drainage, rattlesnake master will grow in many soil types, including clay. It attracts many pollinating insect species and is quite easy to grow from seed. With their arresting presence in the garden, the larger sea hollies can be used as spec-
imen plants. Their unique form is best appreciated in an uncrowded setting with only a few companions and perhaps some statuary to help set the scene. Sea hollies that produce masses of smaller flowers lend themselves to more traditional uses in the perennial garden. Choose colorful companions that prefer the same growing conditions of full sun and well-drained soil. Good choices include yarrow, coneflower, butterfly weed, crocosmia, tickseed (Coreopsis), and ornamental grasses. Karen Bovio is the owner of Specialty Growers in Howell, MI.
Eric Hofley / Michigan Gardener
âBlue Hobbitâ (E. planum âBlue Hobbitâ) is a dwarf sea holly that grows to only an 8- to 12-inch round mound.