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Sea Holly Plant Care: How To Grow A Sea Holly Plant

By Nikki Tilley, Author of The Bulb-o-licious Garden

Looking for a fascinating addition to the garden? Then why not consider growing sea holly flowers. Sea hollies can provide unique interest. Read this article for information about growing Eryngium plants.

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Sea holly

Common Name: Sea holly
Genus: Eryngium
Species: x oliverianum
Skill Level: Beginner
Exposure: Full sun
Hardiness: Hardy
Soil type: Well-drained/light, Clay/heavy, Dry, Moist, Sandy
Height: 90cm
Spread: 45cm
Time to divide plants: March to May
Flowering period: July to September

Sea hollies are striking plants for a summer border but only thrive where drainage is particularly good - they will not tolerate winter wet. E. x oliveranum is one of the most useful, having large vivid blue flowers with dark green, clearly veined leaves forming a loose rosette at the base of the plant. It survives in a wider range of soil types than many more difficult eryngiums, and can even cope with poor gravelly soil and heavier ground if it never becomes waterlogged. The flowers attract bees and other insects, and are good for cutting or drying. The Royal Horticultural Society has given it its Award of Garden Merit (AGM).

Beautiful Blue Sea Holly

I love blue, and this interesting member of the Parsley family is one of the easiest blue flowers I know. Drought-resistant and un-fussy about soil types, Sea Holly is a wonderful addition to any perennial garden.

(Editor's Note: This article was originally published on February 18, 2010. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)

A perennial wildflower native to the Caucasus and Iran, Eryngium comprises about nineteen known species, but the most common are Common sea holly (E. maritimum), Rattlesnake Master (E. yuccifolium), Alpine sea holly (E. alpinum), Giant sea holly (E. gigantium), Mediterranean sea holly (E. bourgatii), Flat sea holly (E. planum), and Zabel eryngo (E x zabelii). Amethyst sea holly (Eryngium amethystinum), shown at right, is striking with its purple-blue heads and stems.

A charming story tells of noted British garden enthusiast, Ellen Wilmott, being so enamored of Sea Holly that she always kept some seeds in her pocket. If she chanced upon a garden she considered to be "boring", she'd scatter a few sea holly seeds and move on. When the seeds sprouted in all the places Miss Wilmott had visited, the plant became affectionately known as "Miss Wilmott's Ghost."

Each species has its own distinct bracts and foliage, from stickery and spiky bracts to heart-shaped or holly-shaped leaves, but all species have a lovely gray or green or silvery foliage and stems. From as small as 12 inches tall to those reaching 4', Eryngium can fit into almost any garden space. But the beauty of this plant is not just in its striking contrast to the plants around it, but the ease with which it can be grown and maintained.

Average well-drained soil in full sun is all it needs, and it will even tolerate sand and gravel. Seeds can be sown outdoors in the fall, or indoors in winter however, winter sowed seed flats will have to be refrigerated for 4 to 6 weeks before allowing the seeds to germinate. Additionally, plants started from seed may not bloom the first year. Plants are often available from mail-order catalogs and some garden centers, and Dave's Garden Plant Traders usually has several for trade. Literature cautions that the plant does not transplant well, so be sure of the location before sowing seed or setting out plants. Bloom begins in July and continues profusely through September or October, depending on region. The U.S. cultivars do well in zones 5 to 9.

Interesting Facts and Lore About Sea Holly

  • In the 17th and 18th centuries, herbalists candied the roots and touted them as an aphrodisiac.
  • The extensive root system of sea holly is useful in erosion control.
  • The root is used as a diuretic, expectorant, stimulant, and tonic in today's array of natural remedies.
  • Flowers and foliage are excellent for drying and in floral arrangements.
  • Leaves and roots are edible.
  • Deer dislike sea holly.

Sources for Plants and/or Seed

Eryngium (Sea Holly)

Sea holly (Eryngium) is a spiky, stiffly branched, architectural plant, perhaps best given space to make its own statement, ideally in a gravel garden. It will also integrate in mixed, sunny borders, providing an excellent contrast to softer plants. If you are growing a blue sea holly plant in containers, place them with other plants that can tolerate dry conditions. Some of them are biennials. This striking plant has deeply cut, bluish-grey leaves, veined white, and spiky steel-blue cones of flowers. Cultivars, which vary in height and the exact shade of blue, include ‘Blue Glitter’, ‘Sapphire Blue’ and ‘Big Blue’.

Sea holly should be grown in full sun and in light, well draining soil. Sea holly does not like to be disturbed so choose a spot where it will not need transplanting.

The plant produces a long tap root which makes transplanting or division difficult, but also serves to make it a very drought tolerant plant. Sea hollies have an upright growth habit from two to six feet, depending on the variety, and flower repeatedly from midsummer into fall.

During the first year, sea holly needs more specialized care than it will in subsequent growing seasons. Once the soil has warmed in the spring, direct seed it into your garden bed or container or use young plants from the nursery. Water well after planting and mulch the area to retain moisture. In its second and subsequent years, the sea holly does not require weekly watering. In fact, take special care not to over-water the plants. Once established, the sea holly is tolerant of dry soils.

Sea holly fits well with plants from arid regions, making it suitable for desert, Southwestern or Mediterranean themed landscapes. Surround it with succulents and other species that are known for their foliage as much as their flowers.

This ornamental plant looks beautiful in flower arrangements – both fresh and dried. For dried use, cut stems just as the first few flowers in each umbel are almost fully opened: hang upside down in a dark, warm room to dry.


The many species and cultivars of sea hollies all share similar growing requirements. They like full sun and well-drained soil. They thrive in poor, sandy soil and are extremely drought-tolerant.

They are one of those special plants that performs better without fertilizer, compost or irrigation. Transplants are available in many nurseries, but if they can't be found, try one of the following seed companies for a good selection of sea holly varieties. Sea holly is easy to grow from seed and should be sown directly on the surface where it is to grow.

  • Swallowtail Garden Seeds sells several varieties with 15 to 40 seeds per pack for less than $5 each.
  • carries Blue Star sea holly seeds at approximately $2 for 25 seeds.

Care and Maintenaance

Sea holly is untouched by pests and disease. It needs a bit of water to get established, but little ongoing care is required. The dried stems provide winter interest in the garden, but should be cut to the ground before new growth begins each spring. In rich soils the plants may flop over and require staking.

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