Alphabetical Plant Listing

Eryngium planum (Flat Sea Holly)

Blue Eryngo, Flat Sea Holly


Flat Sea Holly (Eryngium planum) provides a tremendous garden presence throughout the summer that can't be overlooked with its profuse egg-shaped, steel-blue colored flowers. Its beautiful texture, unique color, long-lasting flowering, easy care and beauty in dried flower arrangements make it a favorite of gardeners. A favorite of bees too!

  • Eryngium planum is a miniature form of Eryngium, as regards its flower heads, which measure about 2 inches across (5 cm) and are blue all over. It grows in clumps of stiffly erect, branched stems, up to 3 feet tall (90 cm), which gives the plant the appearance of an elegant little bush.
  • With a trend toward drier summers, Eryngium has become even more popular. Easy to please, even in dry gardens where other border stalwarts suffer, Eryngium goes from strength to strength over the entire summer, complimenting every other plants with its silver bracts.
  • Eryngium partners well with Mediterranean plants and silver foliage plants.
  • Eryngium planum thrives in full sun in dry, sandy, well-drained soils. The sunnier the site, the more intense the blue! Tolerates poor soils. Avoid planting this plant in moist and fertile soils, where it will tend to sprawl and may require support.
  • Drought tolerant, deer and rabbit resistant
  • Excellent choice for sun baked, informal beds and borders or natural plantings, where the steel blue flowers and foliage will superbly complement the vibrantly colored summer flowers. Ideal for small gardens. May be planted as a single specimen or in groupings. Perfect for cut or dried flower arrangements too!
  • Deadhead to preserve a neat appearance. Cut back in late summer after flowering is over.
  • Self-seeding may happen under satisfactory growing conditions, but rarely becomes a nuisance.
  • Transplants poorly and is best left undisturbed once established.

Learn How To Plant, Care, and Grow Spectacular Sea Holly (Eryngium)

Attractive, Sea Holly plants (Eryngium) are striking ornamental perennials grown for their arresting, thistle-like, silvery or blue tinted flower heads adorned with a ruff of showy bracts. Blooming in summer and sometimes into fall, they are exceptionally care-free plants if they are given a well-chosen site. Here are some basic rules that need to be followed to enjoy their splendid flowers.
Read More

Guide Information

Hardiness 4 - 8
Heat Zones 1 - 12
Plant Type Perennials
Plant Family Eryngium - Sea Hollies
Exposure Full Sun
Season of Interest Summer (Early,Mid,Late)
Height 8" - 3' (20cm - 90cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 12" - 18" (30cm - 45cm)
Water Needs Low
Maintenance Low
Soil Type Chalk, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Well-Drained
Characteristics Dried Arrangements, Cut Flowers, Showy
Tolerance Deer, Drought, Rabbit, Dry Soil, Salt
Attracts Butterflies
Landscaping Ideas Beds and Borders, Patio and Containers
Garden Styles Coastal Garden, Gravel and Rock Garden, Informal and Cottage

Photo: / 123RF Stock Photo

While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.

Guide Information

Hardiness 4 - 8
Heat Zones 1 - 12
Plant Type Perennials
Plant Family Eryngium - Sea Hollies
Exposure Full Sun
Season of Interest Summer (Early,Mid,Late)
Height 8" - 3' (20cm - 90cm)
Spread 1' - 2' (30cm - 60cm)
Spacing 12" - 18" (30cm - 45cm)
Water Needs Low
Maintenance Low
Soil Type Chalk, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Well-Drained
Characteristics Dried Arrangements, Cut Flowers, Showy
Tolerance Deer, Drought, Rabbit, Dry Soil, Salt
Attracts Butterflies
Landscaping Ideas Beds and Borders, Patio and Containers
Garden Styles Coastal Garden, Gravel and Rock Garden, Informal and Cottage
Not sure which Eryngium - Sea Hollies to pick?
Compare All Eryngium - Sea Hollies
Great Plant Combination
Ideas with Eryngium - Sea Hollies
Guides with Eryngium - Sea Hollies

Find your Hardiness Zone

Find your Climate Zone

Find your Heat Zone

Join Gardenia.net

Create a membership account to save your garden designs and to view them on any device.

Becoming a contributing member of Gardenia is easy and can be done in just a few minutes. If you provide us with your name, email address and the payment of a modest $25 annual membership fee, you will become a full member, enabling you to design and save up to 25 of your garden design ideas.

Join now and start creating your dream garden!

Create a New Collection

Optional. For your reference.


Move Selected Plants to a Different Collection


Delete Collection

This field is required.