Sea Holly

Eryngium
A genus of perennial plants that are excellent for the xeroscape garden. The are very tolerant of drought and heat as well as alkaline and saline soil. While drought tolerant - they look better if they do not go more than 2 weeks without water.
Sea Holly is not generally eaten by deer or rabbits. Cut back dead foliage before winter otherwise collecting moisture may rot the crown if the winter is excessively wet. They do not like root disturbance and division is not recommended though can be done during early spring.
Root cuttings can be taken during late winter. The roots should be cut in 3 inch pieces and planted 0.8 inches deep.

* photo taken on August 3 2010 @ University of Guelph Arboretum, Ontario

* photo taken on June 30 2013 @ U.S. National Arboretum, DC

* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014

* photo taken bu Clarence A. Rechenthin @ USDA-NRCS PLANTS Database

* photo taken on July 11 2014 in Washington, DC

Eryngium agavifolium
A deep-rooted, thick clump-forming, evergreen perennial, reaching a maximum size of 6 x 4 feet, that is native to Argentine grasslands.
The toothed, sword-shaped leaves, up to 30 x 3 ( rarely over 18 ) inches in size, are glossy green.
The leaves resemble that of the Agave.
The greenish flowers, up to 2 inches across, are surrounded by small bracts.
The flowers are borne all summer long.
Hardy zones 6 to 9 ( possibly to 4 on protected site with thick winter mulch ) in full sun on fertile, very well drained soil only. Very tolerant of drought.

* photo taken on 4th of July 2010 in Washington, D.C.


Eryngium alpinum ( Alpine Eryngium )
A semi-evergreen, tap-rooted perennial, reaching a maximum size of 4 x 3 feet, that is native to to Europe from western France to the Balkans.
The deeply-lobed, heart-shaped basal leaves, up to 10 x 5 inches in size, are blue-green.
The globular metallic-blue flowers, up to 2 inches across, are surrounded by finely-divided violet-blue bracts. The flowers are borne on thick, blue stems from mid to late summer.
Hardy zones 3 to 8 in full sun on well drained soil.

Eryngium amethystinum ( Amethyst Sea Holly )
A semi-evergreen perennial, reaching a maximum size of 3 x 3 feet, that is native to southern Europe ( the island of Sicily to the Adriatic ).
The spiny, palmate-lobed, thistle-like leaves are up to 10 inches in length.
The abundant, narrow, bright blue ( bracted deeper blue ) flowers, up to 0.3 inches, are borne on steel-blue stems. The flower bracts are up to 2 inches in length, they are borne mid to late summer.
The flowers are loved by bees.
Hardy zones 2 to 7 in full sun on dry, sandy, well drained soil.

Eryngium aquaticum
A perennial that is native to brackish marshes in the eastern U.S. from New Jersey south to Florida.
The silvery-white flowers are borne during mid summer.
Hardy zones 6 to 8 in full sun on wet soils. It is very flood tolerant.

* photo taken on Aug 24 2017 @ U.S. Botanic Garden, Wash. DC.

Eryngium 'Blue Sapphire'
A deep taprooted, sterile hybrid, reaching up to 3 x 2 feet in size .
The foliage is steel-blue.
The steel-blue flowers are larger than that of other Eryngiums.
Hardy zones 2 to 8 in full sun on well drained soil.

Eryngium bourgatii ( Mediterranean Sea Holly )
A tap-rooted perennial, reaching a maximum size of 32 inches x 2 feet, that is native to the Pyrenees Mountains in southwestern Europe. A subspecies is native to Turkey.
The crisped, spiny, thistle-like leaves, up to 3 inches across, are gray-green with white veins.
The light blue flowers inflorescences, up to 1 inch in size, are surrounded by up to 12 steely blue bracts. The flowers are borne mid to late summer.
Hardy zones 5 to 8 in full sun on just about any dry, well drained soil.

* photo taken on 4th of July 2010 @ U.S. National Arboretum, D.C.


Eryngium campastre
A perennial, reaching up to 2 feet in height, that is native from Europe to southwestern Asia.
The foliage is pale blue.
The bluish-white spiny flower bracts are up to 1.8 inches in length.

Eryngium giganteum ( Miss Willmotts Ghost )
A self seeding biennial to perennial, reaching a maximum size of 6.5 x 4 feet, that is native to Iran.
The heart-shaped basal leaves are up to 12 inches in length. The foliage is mid-green.
The silvery-blue flower inflorescences with long silvery-white bracts are borne on plants after a few years. The flowers are borne all summer long. The plant usually dies after it produces seed.
Hardy zones 4 to 9 in full sun to partial shade.

Eryngium horridum
A perennial, reaching up to 10 x 3 ( rarely over 7 ) feet, that is native to Brazil and Argentina.
The strap-shaped leaves are up to 40 x 1.2 inches in size. The foliage is mid-green.
The creamy-green flower balls, up to 0.5 inches across, are borne in masses.
Hardy zones 8b to 10 ( tolerating as low as 14 F ) in full sun on fertile, very well drained soil. It prefers hot summers or in cooler maritime regions a warm south facing wall.

Eryngium leavenworthii

* photos taken on Sep 3 2017 @ U.S. National Arboretum, D.C.

Eryngium maritimum ( Sea Holly )
A perennial, reaching a maximum size of 3 x 3 feet, that is native to sand dunes on coastal regions of Europe including the British Isles, Mediterranean and Black Sea coasts.
The thick, spiny leaves are very glaucous, blue-gray.
The steel-blue flowers have large silvery bracts.
Hardy zones 5 to 8 in full sun on just about any deep, well drained soil including pure sand which it is often found on in the wild.

* photo taken on July 25 2015 @ Niagara-on-the-Lake, Ontario

Eryngium x oliverianum
A herbaceous perennial, reaching a maximum size of 5 x 2 feet. It often needs to be staked.
The spiny, toothed, cordate basal leaves are blue-green.
The bluish inflorescenes, up to 4 inches in length, have narrow blue bracts.
The flowerheads themselves are up to 1.6 inches across, and are surrounded by up to 15 narrow, spiny bracts that are purple in color.
Hardy zones 5 to 9 in full sun to partial shade on a deep, light, well drained soil.

* historic archive photos

Eryngium pandanifolium
A huge perennial, reaching up to 13 x 6 ( rarely over 10 ) feet, that is native to marshland in South America ( Paraguay to southern Brazil; south to Uruguay and Argentina ).
The gigantic, spiny sword-like leaves are up to 8 feet x 1 inch in size. The foliage is blue-green.
The reddish-purple flower heads are borne during late summer.
Hardy zones 8b to 9 ( tolerating as low as 14 F ) in full sun on moist, deep, rich, well drained soil. Propagation is from root cuttings or division.

Eryngium planum ( Flat Sea Holly )
A long lived, bushy, evergreen perennial, reaching a maximum size of 4 x 3 feet, that is native to Eurasia ( from Germany to Russia; south to Austria to the Caucasus and central Asia ). The heart-shaped basal leaves, up to 8 inches in length, are deep green.
The light blue, oval flower inflorescences, up to 0.3 inches in length, are surrounded by narrow blue-green bracts. The flowers are borne mid to late summer.
Hardy zones 2 to 9 in full sun on sandy, well drained soil. Extremely cold tolerant, it is known to thrive as far north as Peace River in Alberta. Drought tolerant and unlike other species, it is also tolerant of moist soil.

* photo taken on Aug 2 2013 in Stratford, Ontario

'Jade Frost'
More compact in habit, reaching up to 2.5 feet in height.
The foliage is blue-green with bold creamy-white, often pink tinged edges.
Hardy zones 5 to 8

Eryngium serra
Similar to Eryngium agavifolium. An evergreen perennial, reaching a maximum size of 6.5 x 4 feet, that is native to southern Brazil and Argentina.
The spine-edged, sword-shaped leaves, up to 2 feet in length, are green.
The greenish-white flowers, up to 2 inches across, are surrounded by small bracts. They are borne during late summer.
Hardy zones 6 to 9 in full sun. Propagation is from root cuttings or division.

Eryngium tripartitum
A tap-rooted perennial, reaching a maximum size of 4 x 3 feet, that makes an excellent border plant. It is native to the Mediterranean sea region.
The sparsely spined, toothed, ovate basal leaves are deep green veined gray-green.
The spiny, globular, steel-blue inflorescences, up to 0.3 inches across, are borne on spreading branches during late summer.
The wiry stems are blue.
Hardy zones 5 to 8 ( 3 to 4 on protected sites ) in full sun on sandy, well drained soil.

Eryngium variifolium ( Moroccan Sea Holly )
An evergreen perennial, reaching a maximum size of 4 x 3 ( rarely over 2.5 ) feet, that is native to Morocco in northern Africa.
The sparsely-spined, basal leaves, are glossy deep green and marbled white.
The pale blue inflorescences, up to 0.8 inches across, are surrounded by up to 7 narrow, silvery bracts.
Hardy zones 4 to 9 in full sun on very well drained soil. Very drought tolerant.

Eryngium yuccifolium ( Rattlesnake Master )
A striking, evergreen perennial, reaching up to 6 x 5 ( rarely over 4 ) feet, that is native to open woods and grasslands in eastern North America ( from Nebraska to southern Minnesota to Connecticut; south to central Texas to southern Florida ). It is endangered in Nebraska, Minnesota, Michigan and Ohio. It is extinct in the wild in Maryland & New Jersey. It generally only occurred sporadically on the Ohio shore during the 1800s but was abundant locally southeast of the town of Kimball.
The spine-edged, Yucca-like leaves, up to 40 x 1.6 inches in size, are waxy glossy silvery-green. The spines edging the leaves can be up to 2 inches in length.
The creamy-green bracted, globular flower heads, up to 3 inches long, are borne during mid-summer to early autumn.
Hardy zones 3 to 8 in full sun to partial shade on dry, well drained soil. Tolerant of drought and hot humid summers. Propagation is from seed, root cuttings or division.

* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014

* photo taken on Oct 21 2014 @ U.S. Botanical Gardens, Washington, DC

* photo taken on Sep 3 2017 @ U.S. National Arboretum, D.C.

* photos taken on Aug 4 2021 @ U.S. National Arboretum, Washington, DC

* photo taken on July 24 2021 in Columbia, MD

* photo taken on Sep 3 2024 in Columbia, MD

* photo taken by Bill Summers @ USDA SCS. 1991. Southern wetland flora

Eryngium x zabelii
A sturdy perennial, reaching a maximum size of 32 inches x 2 feet.
The crisped, spiny, thistle-like leaves are gray-green with white veins.
The light blue flowers inflorescences, up to 1 inch in size, have steely blue bracts.
The flowers are borne during summer.
Hardy zones 2 to 8 in full sun on very well drained soil. Tolerates dry sandy soil and is great near the sea.

* historical archive photo

Eryngium 'Big Blue'
A vigorous hybrid, reaching up to 2.6 x 2.5 feet, with silver spiky foliage borne on blue stems.
The blue flowers are surrounded by iridescent blue bracts. The entire flower structure, up to 4 inches across, peaks during mid summer.
Hardy zones 3 to 9 ( possibly 2 ) in full sun on well drained soil. Drought tolerant.

* photo taken on July 10 2024 @ Brookside Gardens, Wheaton, MD

'Donard Variety'
Reaches up to 3.5 x 3 feet with huge, cone-like, blue flowers, up to 4 inches in length.

'Neptune's Gold'
Reaches up to 2 x 1.3 feet in 4 years, eventually slightly wider, with intense golden-green foliage. The leaves average 3.8 x 4.2 inches in size.
The flowers are bright blue
Hardy zones 4 to 8

* patent photo