Eryngium

( ehr - RIN - jee - um )

At-A-Glance Information

Also called Sea Holly, Eryngo or Amethyst Eryngium, this genus of annuals, biennials and perennials need full sun and have varying water requirements depending on the species. The flowers will attract bees and other pollinators to your garden, producing thistle-like stalks and flowers with showy bracts. They are summertime bloomers for the most part, and the upper parts of the plant may be dusted in silver or tinted blue or purple. They are fantastic for rock gardens and along beach walkways, and are great choices for dried flower arrangements. In the language of flowers (Floriography), Eryngium represents admiration.

Eryngium Species and Varietals

The genus Eryngium is a member of the plant family Apiaceae and includes around 250 distinct species. Sea Holly grows best in zones 2-24, though some species have more specific zone requirements. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Eryngium alpinum (Alpine Sea Holly, Apline Eryngo, Queen of the Alps)
This perennial is native to southeastern Europe and gets 2.5 feet tall and 1.5 feet wide, bearing upper leaves and stems that are tinted blue. Flower heads are conical, and surrounded by bracts. Variety 'Blue Star' has prominent metallic-blue flowers and leaves. This species can tolerate light shade and needs regular water.

Eryngium amethystinum (Amethyst Eryngo, Italian Eryngo, Amethyst Sea Holly)
This perennial grows best in zones 1-24 and hails from Italy and the Balkans. Gets to 2.5 feet tall and 1.5 feet wide, with green leaves and silvery blue stems. Flower heads are amethyst in color, and are surrounded by silvery-blue bracts. These will attract butterflies to your garden and need moderate amounts of water for best performance.

Eryngium aquaticum (Rattlesnake Master, Marsh Rattlesnake Master, Corn-Snakeroot, Bitter Snakeroot, Marsh Eryngo)
Native to eastern areas of North America, this species reaches up to 6 feet tall and prefers to grow in wet soils around bogs, marshes, and ditches. Flower inflorescences are white to blue with spiny, blue-tinged bracts. These plants are commonly used in dried flower arrangements and as garden ornamentals around water features.

Eryngium aristulatum (California Eryngo, Jepson's Button Celery)
This California and Baja California native plant grows in wet areas, such as near natural pools and in floodplain meadows. It is also found in wooded forest areas, marshes and wetlands. They can reach a bit over 3 feet tall when mature, and produce white-petaled flowers with purple styles and spiky bracts. The typical blooming period for this species is from June through August.

Eryngium armatum (Coastal Eryngo, Prickly Coyote Thistle)
Endemic to the coastal regions of northern and central California, these plants form basal rosettes of green foliage and stout, fleshy stems topped with green-bracted flower inflorescences of insignificant purple to white flowers.

Eryngium articulatum (Beethistle, Jointed Coyote Thistle)
Native to an area spanning from California through Idaho, this species grows in marshes and along riverbanks. These plants reach over three feet tall when mature, and produce rounded egg-shaped flower heads. Blooms are tiny and lavender-colored, tucked in amongst greyish-green bracts.

Eryngium baldwinii (Baldwin's Eryngo, Kissing Comfits)
This spreading groundcover species of Eryngium produces tiny light blue flower heads and prefers moist soil and a lot of sun. These plants are native to Florida and Georgia, and the species is named for American physician and botanist William Baldwin).

Eryngium billardieri
This biennial aromatic herb is native to Turkey, Lebanon, Iran, Iraq, Afghanistan, Pakistan and the Turan Region in the Middle East. It is used as a medicinal plant in its native region, known for its use in hepatitis and fatty liver disease treatments.

Eryngium bourgatii (Mediterranean Sea Holly, Pyrenea Eryngo)
This species is native to Andorra, France and Spain and reaches between 6 and 18 inches tall at maturity. Flowers are deep purple-blue and are surrounded by spiny silvery purple bracts. Cultivar 'Oxford Blue' is a great garden ornamental.

Eryngium campestre (Field Eryngo, Watling Street Thistle)
These thorny plants have light whitish-green foliage and produces flowers between July and September. This species is native to central and southern Europe.

Eryngium constancei (Loch Lomond Button Celery, Loch Lomond Coyote Thistle)
This species is native to northern areas of the San Francisco Bay area in Northern California, appearing in vernal pools. It is an endangered species of Eryngium. These plants reach between 8 and 12 inches tall at maturity, and produces white flowers with sharp bracts.

Eryngium ebracteatum (Burnet-Flowered Sea Holly)
These plants are native to damp grasslands in South America, and are occasionally cultivated as ornamental plants. Flowers do not have bracts and are deep wine-red.

Eryngium foetidum (Culantro, False Coriander, Long Coriander, Burmese Coriander, Sawtooth Coriander, Ngo Gai, Cimarron, Recao, Chardon Beni, Bandhaniya, )
This is a biennial plant, but is grown as an annual (if temperatures drop below 0 degrees Fahrenheit). These plants grow best in zones 4-9, 12-24, H1 and H2 and are native to the tropical parts of the Americas. They reach 2 feet tall and wide, and produce rosettes of leaves that sprout flowering stems with dark green flower heads. This species needs fertile soil and regular water. The plants are fragrant, reminiscent of cilantro, and the succulent leaves can be used as a substitute for the herb.

Eryngium giganteum (Miss Wilmott's Ghost)
This is a biennial or short-lived perennial, native to the Caucasus and Iran. These plants reach 3-4 feet tall and 2 feet wide. Medium green leaves and pale green flower heads surrounded by silvery bracts create a nice contrast. These plants will die off after flowers expire, but reseed well and will return the next growing season. They need fertile soil and regular waterings.
Eryngium spp. Hybrids and Cultivars
This group of Eryngium plants includes cultivars bred for interesting flower colors, tolerances, or other characteristics. Various cultivars are listed and described below:
'Big Blue'
​A variety with large, intense blue flower cones. Grey-green foliage.
'Blue Hobbit'
​Compact cultivar with steel-blue small flower heads.
Eryngium x tripartitum
Violet stems support small dark blue flowers.
'Jade Frost'
A cultivar with variegated foliage.
'Jos Eijking'
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'Neptune's Gold'
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'Picos Blue'
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Eryngium leavenworthii (Leavenwoth's Eryngo)
Native to the central United States, this species of Eryngo reaches up to 3 feet tall and prefers to grow in prairies, fields, and open woodland areas. Typically, flowers emerge between the months of July and September, but they are known to flower as late as November. Flowers are purple to wine-colored and have purple bracts. The species is named for its discoverer of record, Melines Conklin Leavenworth.

Eryngium maritimum (Sea Holly, Sea Eryngo, Sea Eryngium)
Native to most European coastlines, this species produces a clump-forming plant with blue-white flowers and green stiff, spiny, leathery leaves. Flowering occurs from June through September in the plant's native range. 

Eryngium mathiasiae (Mathias' Eryngo, Mathias' Button Celery)
Named for Californian botanist Mildred Esther Mathias, this species is endemic to the Modoc Plateau in northeastern California. These plants prefer to grow in vernal pools and ditches, and reach around 12 and 16 inches tall when mature. Flowers are greenish-white and inflorescences are surrounded by sharp bracts.

Eryngium pandanifolium (Pandan-Like-Leaved Eryngo)
Native to Brazil, Paraguay, Uruguay, and Argentina, this species has been introduced to and is thriving in Australia, New Zealand, and Portugal. It is classified as an invasive species in some areas of the world, so check with your local authority before importing or planting. These are interesting pants that form basal tufts of strappy light green foliage and produce purple flowers.

Eryngium pendleteonense (Pendleton Button-Celery)
Endemic to San Diego County, California, this species of Eryngo grows in moist coastal grasslands and coastal sage scrub habitats. It was first described in 1999 and is a low-grower that spreads to about 16 inches wide. These plants can form small colonies of a few individuals, which appear as one plant. This species is considered rare and critically imperiled.

Eryngium pinnatisectum (Tuolumne Eryngo, Tuolumne Button Celery)
This uncommon species is native to the counties of Amador, Sacramento, Calaveras, and Tuolumne in California. Individual plants reach up to a foot and a half tall, and have pale greenish-white flowers that bloom from May through August. This species is considered endangered due to habitat loss.

Eryngium planum (False Sea Holly, Blue Eryngo, Flat Sea Holly)
This species is a perennial that gets to 3 feet tall and 1.5 feet wide. It is native to Europe and Asia, and has deep green leaves on tinted-blue stems. Flower heads are light blue, surrounded by narrow blue-green bracts. Varieties include 'Blaukappe' (with intense blue color), and 'Silver Salentino' (with silvery white blooms). This species requires moderate water for best performance.

Eryngium prostratum (Creeping Eryngo)
Native to the southeastern United States, this low-growing species of Eryngo produces blue flower heads from summertime through the first frost of the year.

Eryngium racemosum (Delta Eryngo, Delta Button Celery)
Native to the Sacramento-San Joaquin River Delta in California, this species is considered critically imperiled due to habitat destruction and competition from non-native species in its native area. These plants are mostly prostrate, spreading to reach about a foot and a half wide. Stems can root at nodes if grown in moist soil. Flowers are white to purple-tinged and are surrounded by spiny bracts.

Eryngium spinosepalum (Spinysepal Eryngo, Spiny-Sepaled Button Celery)
These plants can be annual or perennial and are endemic to California's San Joaquin Valley. This species reaches about 30 inches tall and produces white to purple-tinged flowers in April and May.

Eryngium vaseyi (Coyotethistle)
Endemic to California, this species does well in the Central Valley and Central Coast Ranges and the southern California coast. These plants can be either decumbent or upright, and produce white-green flower heads.

​Eryngium varlifolium (Moroccan Sea Holly)
This perennial grows best in zones 4-9 and 14-24 and is native to Morocco. It gets 1.5 feet tall and just 10 inches wide. Leaves are a bit fleshy, and are a marbled dark green. Stems are stiff and silver-blue, holding blue-grey flower heads surrounded by silvery bracts. This species needs moderate to regular water.

Eryngium yuccifolium (Rattlesnake Master, Button Snakeroot, Button Eryngo)
This species is perennial and is native to the central and eastern united states, growing to 4 feet tall and 2 feet wide. Blue-gray leaves reach over three feet long, and stems are strong and have a branching habit. White-green to pale blue flowers do not have showy bracts. These need fertile soil and regular waterings.

Caring for Eryngium

Choose the spot to grow Eryngium carefully before installing; most species grow from large underground taproots and do not like to be disturbed or moved once they are growing. Grow Eryngium plants in a space in the garden that receives full sun. Ideally, this means they should be getting between 6 and 8 hours of sun each day.  If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. They prefer moderately dry, somewhat fertile soils with a pH of between 6.1 and 7.8. Good drainage is critical; these plants do not like to have their roots in standing water at any time. The exception is Giant Sea Holly (Eryngium pandanifolium) which does prefer soil to be somewhat moist. Other species will suffer from root rot and die off when soil is kept moist, so make sure that you are aware of which species you are cultivating. Water new plantings regularly as they establish a strong root system. At maturity, most species are very drought-tolerant, able to pull nutrients and water from their large taproots.

Each year in springtime, apply a 2-inch layer of organic compost around the planting area to improve soil structure, drainage, and nutrient load. This feeding should be sufficient to provide these flowers with enough nutrients to get through their growth and flowering seasons with ease. ​Pruning these plants is relatively straightforward; simply remove flowering heads after blooms have faded to clean up the look of plants. Dried flower heads can be aesthetically pleasing when left on the plant, but some species tend to re-seed vigorously, and the only way to combat this issue is to deadhead. Deadheading will also encourage more blooms to emerge. At the end of the growing season, cut the plant back to just above ground level with clean, sharp pruners.

Harvesting Eryngium
Culantro, or Eryngium foetidum, is a biennial plant that is grown as an herb. Culantro leaves have a very strong flavor, so they are used in small amounts, and are used in many different cuisines. The plant goes by many names, including Long Coriander, False Coriander, Recao (Spanish), Langer Koriander (German), Ngo Gai (Vietnamese), Pak Chi Farang (Thai), and Bhandhanya (Hindi). To harvest fresh leaves, simply cut large, outer leaves individually using a clean, sharp knife. To process and preserve the entire plant, cut the rosette at soil level, and then pull or cut all of the leaves off of the plant. Place the leaves in a food processor and add oil to moisten the blend. Once chopped, it can be stored in the freezer with a layer of olive oil on top to prevent the leaves from getting freezer burn. Whenever Culantro is needed to flavor a dish, simply chip a bit off of the frozen block and defrost.

Propagation

Eryngium, or Sea Holly, is best propagated via seed. There are many species that will re-seed freely if spent flowering heads are not taken off of plants before they release their seeds. Dividing these plants is an option, though they do not like to be disturbed once planted, so seed propagation is the main method. To seed-propagate your Sea Holly plant, follow the instructions below:

Propagating Eryngium by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows. 
  2. Harvest your seeds. The seed pods on Eryngium plants are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
  3. The seeds will need a period of cold-stratification in order to germinate well. To complete this process, place seeds in a bag or other sealable container filled with peat moss or sand that has been moistened, but is not soggy. Place the container in the refrigerator (or another place that stays around 40 degrees Fahrenheit). Leave them there for four weeks' time, and then remove them for sowing.
  4. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes between 3 and 4 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  5. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Eryngium seed heads.
Eryngium seeds.

Problems and Pests

Eryngium plants can have issues with the following pests and diseases in the garden:
  • Snails and Slugs
  • Aphids
  • Powdery Mildew
For more information, including treatments and management, consult the following pages:
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Gallery

Eryngium leavenworthii making a bright pink statement in this mixed bed.
Eryngium plants are great for pollinators.
Here, a white-bracted Eryngium is grown in mass along a walkway for dramatic effect.
This mixed bed includes Eryngium, Stipa, and Beardtongue.
Eryngium represents one of the few plants that exhibits blue flowers and bracts.
Lighter-colored Eryngiums are wonderful as accents to other plants, like purple Salvia.

Videos

All about Sea Holly.
Lean how to grow these interesting plants from seed.
Planting Sea Holly bare roots.
These almost alien-looking plants are standouts in the landscape.

Resources

Sea Holly Plant Care: How to Grow a Sea Holly Plant
How to Grow and Care for Sea Holly
How to Plant and Grow Sea Holly
Learn How to Plant, Care, and Grow Spectacular Sea Holly (Eryngium)
Wikipedia: List of Eryngium Species
Wikipedia: Eryngium
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 307-308, Eryngium
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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