Eryngium 

(air-in' gee-um)

Common name: Sea Holly

Family: Apiaceae, Carrot

Height x width: 1½-2' x 1½-2'

Growth rate, habit: moderate; upright

Foliage: alternate, upper leaves clasping or sessile, lower basal leaves obovate to ovate, variable with species; spiny (spinose), deeply toothed or dissected, often white veined

Flowers: summer, blue heads ½-¾" long and surrounded by 9-15 long, lanceolate involucral bracts making an unusual teasel-like collar around the central flower

Hardiness: zones 3 or 5 -8

Soil: well-drained, prefers sandy and dry

Light: sun

Pests and problems: smut, leaf spots, stem rot (none common or serious)

Landscape habit, uses: foliage or flowers as specimen or emphasis plant, bold texture, dried flowers

Other interest: native to Europe and the Mediterranean; from the Greek word for thistle from its flower resemblance

Other culture: relatively care-free, good for difficult situations-- deserving of wider use; resents moving due to long taproot; if terminal stem is cut flowering side stems often develop

Propagation: root cuttings, division is difficult due to long taproot, seed (10,000 seeds per ounce) although cultivars don't come true reliably from seed, seeds require a warm moist stratification for one month followed by one month of cold moist stratification

Species:

Of the 200 or so species, found mainly in the Mediterranean regions, the following are most commonly seen as ornamentals.

alpinum (al-pie' num)--Alpine Sea Holly, 1-3', heart-shaped basal leaves, zones 4-7, native to Europe, one of bluest of genus both flowers and stem

amethystinum (a-meth-stee' num)--Amethyst Sea Holly, 1-1½', pinnately divided basal leaves, zones 2-8, native to Europe, most cold hardy of genus, metallic blue flowers and stems branched near top

bourgatii (boor-gatt' ee-ii)--Mediterranean Sea Holly, 1-2', palmate 3-5 divided basal leaves, zone 5-7, native to Pyrenees, blue-green flowers with many silver bracts, white veins in coarse spiny leaves

giganteum (gii-gan' tee-um)-- Miss Wilmott's Ghost, 4-6', heart-shaped basal leaves, zones 4-7, native to Caucasus, needs staking, large flowers to 4" long with silver bracts; named for famous English gardener Ellen Wilmot in early 1900's who liked this plant and would scatter seeds in other people's gardens if they didn't have it

x oliverianum (ah-liv-er-ee-aa' num)--hybrid possibly between alpinum and giganteum, 2-3', lower leaves ovate with slight lobes, purple bracts and vivid blue flowers, zones 5-7

planum (plaa' num)--Flat Sea Holly, 2-3', heart-shaped basal leaves, zones 5-8, native to Eastern Europe, many silver-blue flower heads ½" long and oval, popular European commercial cut flower, less ornamental than other species for gardens

x tripartitum (tri-par-tii' tum)--hybrid probably native to the Mediterranean, 3', zones 5-7, 3-lobed basal leaves, metallic blue flowers with blue-green bracts

varifolium (var-i-fol' ee-um)--Moroccan Sea Holly, 1-2', rounded basal leaves, zones 5-8, seldom seen species with attractive white-veined leaves appearing variegated, also unusual in being evergreen, useful small habit

yuccifolium (yuk-ki-fol' ee-um)--Rattlesnake Master, 2-4', strap-like basal leaves, zones 5-9, native to the eastern U.S., creamy chartreuse flowers like buttons and not very showy, narrow parallel-veined foliage like yuccas which is main feature of this species; name from myth that plants could cure rattlesnake bites or drive snakes away

x zabelii (zah-bell' ee-ii)--Zabel Sea Holly, 1½-2', cross between alpinum and bourgatii, flower heads 1-2" long with 10-12 long rigid bracts, very showy
 
 

Cultivars:
 
Cultivars species height flowers, bracts other
'Amethyst' alpinum 2-3' metallic light blue serrated foliage
'Blaukappe' planum 2' deep blue grows from seed
'Blauerzwert' planum 1½-2' deep blue  
'Blue Cap':'Blaukappe'        
'Blue Diamond' planum 1½-2' deep blue  
'Blue Dwarf':'Blauerzwerg'        
'Blue Ribbon' planum 2' blue appearing double  
'Blue Star' alpinum 2-3' lavender-blue grows from seed
'Donard Blue' x zabelii 2' lavender-blue, large  
'Jewel' x zabelii 2' light blue  
'Opal' alpinum 2' silvery-blue  
'Oxford Blue' bourgatii 2' silvery-blue good color for species
'Silverstone' planum 3-4' creamy white  
'Slieve Donart' alpinum 2' light bracts, dark blue  named for Irish nursery
'Spring Hills' x zabelii 2' lavender bracts, long  
'Superbum' alpinum 2-3' dark blue, large grows from seed
'Violetta' x zabelii 2' dark blue  


©Authored by Dr. Leonard Perry, Professor, University of Vermont as part of PSS123 course.

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