By Terry Deem-Reilly, Colorado Master GardenerSM, Colorado State University Cooperative Extension, Denver
Eryngium is a strikingly architectural plant of the family Apiaceae that is native to Iran and the Caucasus. At least 19 species can be found in plant literature; however, only the most commonly-found species will be discussed here with a brief bow to the wild form 'eryngo'.
Plants generally grow 18' to 36' (although one British cultivar reaches six feet!) with a one-foot spread. Green or silver-blue stems end in green or blue cones surrounded by spiky silver, white, green, blue, or violet bracts. Typically, American varieties produce long, narrow leaves, and European varieties show round or lobed foliage. U.S. cultivars are generally hardy to at least Zone 5. Plants attract butterflies.
Many gardeners know this plant as 'sea holly' or 'Miss Wilmott's Ghost,' after the noted British garden devotee Ellen Wilmott. Wilmott was so impressed by E. gigantium that she carried its seeds in her pocket to scatter in gardens that she deemed uninteresting. The seeds sprouted and grew after her visit, ergo, 'Miss Wilmott's Ghost.' Plants grow to 3' and produce large, grey-green flowers with silvery bracts. 'Sea holly' actually denotes E. maritimum, which has very attractive holly-shaped leaves surrounding greenish blue flowers. One cultivar of this plant is 'Sapphire Blue,' whose bracts and flowers are an inky deep blue.
E. yuccafolium ('rattlesnake master,' 'button snakeroot') reaches 24' to 48', and produces flowers in July and August. It produces blue flowers within spiny, blue-green leaves and closely resembles the yucca plant in habit and flower.
E. alpinum produces the largest flowers of this genus, and blooms in June and July. Its thick, 18' blue stems end in blue flowers surrounded by feathery-looking blue bracts.
As Miss Wilmott proved, eryngium grows readily when directly sowed in the garden, but may not bloom the first year if started from seed. The larger mail-order nurseries and a few local sources sell plants of E. alpinum and E. gigantium. Eryngium is a great dried flower - cut the stems when the bracts are half-open for best results.
All cultivars thrive in full sun, moist soil (although a long taproot keeps them going in drought), and good drainage. Try to place them where they won't have to be moved later, due to the difficulty of dislodging the taproot.
Many species of eryngium (commonly named 'eryngo') grow wild throughout the U.S. Maps showing states where each species is found can be viewed at www.plants.usda.gov.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010