Eryngium planum (Flat Sea Holly)

Blue Eryngo, Flat Sea Holly

Eryngium Planum information, Blue Eryngo information, Flat Sea Holly information, Eryngium Blue Glitter, eryngium Blue Hobbit, Eryngium Jade Frost, Dry soils plants, Sandy soils plants, Blue flowers, Blue perennials

Eryngium planum (Flat Sea Holly) provides a tremendous garden presence throughout the summer with its beautiful texture, unique color, and long-lasting flowering.

What is Eryingium planum?

Eryngium planum, commonly known as Blue Eryngo or Flat Sea Holly, is a perennial plant that belongs to the Apiaceae family. It is native to Europe and Western Asia but has been naturalized in other regions.

Habit and Size: Eryngium planum features an upright, clumping growth habit with branched stems. The plant reaches a height of about 2 to 3 feet (60-90 cm) and has a spread of approximately 1 to 1.5 feet (30-45 cm). Its sturdy stems are bluish-green and covered in spiny, thistle-like foliage.

Flowers: The flowers are its most striking feature. They are globe-shaped, bout 2 inches across (5 cm), consisting of multiple tiny flowers surrounded by a spiky, metallic blue bract. The bracts retain their color even after the flowers fade, extending the plant’s visual interest.

Foliage: The foliage of Eryngium planum consists of deeply lobed, dark green leaves. The leaves are sharply toothed and have a spiny texture, contributing to the plant’s unique appearance.

Blooming Season: Eryngium planum blooms from early to late summer, typically starting in June and lasting until August.

Hardiness: Flat Sea Holly is a hardy perennial plant that thrives in USDA hardiness zones 4-8. It can tolerate a wide range of growing conditions, including both hot and cold temperatures.

Uses: Eryngium planum is commonly grown in gardens and landscapes for its ornamental value. Its striking flowers and unique foliage add texture and color to mixed borders, rock gardens, and wildflower gardens. The dried flower heads also make attractive additions to floral arrangements.

Pollinators: The plant is highly attractive to bees and butterflies, making it a valuable plant for pollinator-friendly gardens. The flowers provide a good source of nectar and pollen for these beneficial insects.

Deer and Rabbit Resistance: Eryngium planum is known for its deer and rabbit resistance. The spiny foliage and tough texture of the plant make it less appealing to these animals.

Drought Tolerance: Eryngium planum is relatively drought-tolerant once established. It can withstand periods of dryness and is suitable for xeriscaping or gardens with low water availability.

Guide Information

Hardiness	4 - 8
Heat Zones	1 - 12
Plant Type	Perennials
Genus	Eryngium
Exposure	Full Sun
Season of Interest	Summer (Early, Mid, Late)
Height	8" - 3' (20cm - 90cm)
Spread	1' - 2' (30cm - 60cm)
Spacing	12" - 18" (30cm - 50cm)
Maintenance	Low
Water Needs	Low
Soil Type	Chalk, Loam, Sand
Soil pH	Acid, Alkaline, Neutral
Soil Drainage	Well-Drained
Characteristics	Dried Arrangements, Cut Flowers, Showy
Tolerance	Drought, Deer, Salt, Rabbit, Dry Soil
Attracts	Bees, Butterflies
Landscaping Ideas	Beds And Borders, Patio And Containers
Garden Styles	Coastal Garden, Gravel and Rock Garden, Informal and Cottage

A few beautiful Eryngium planum Cultivars

Eryngium planum ‘Blue Cap’ (Flat Sea Holly)

Eryngium Planum ‘Blue Cap’ (Flat Sea Holly) is a clump-forming perennial with a profusion of small, steel-blue flowers, tightly packed into egg-shaped heads, that light up the garden throughout summer. Each flower is adorned with a spiky collar of narrow bracts. They are produced on silver-blue stems and stand high above the basal rosette of blue-tinged, deeply toothed, smooth textured leaves.

Hardiness	4 - 8
Exposure	Full Sun
Seasons	Summer (Early, Mid, Late)
Height	2' - 3' (60cm - 90cm)
Spread	1' - 2' (30cm - 60cm)

Eryngium planum ‘Blue Glitter’ (Flat Sea Holly)

Eryngium Planum ‘Blue Glitter’ (Flat Sea Holly) is an exceptional perennial that adds a captivating touch to the garden with its abundant, shimmering steel-blue flowers. Held high on silver-blue stems, the egg-shaped flower heads stand out against the blue-green, deeply toothed leaves. This improved variety blooms prolifically and boasts a vibrant blue color, offering a hassle-free option for gardeners in warmer climates.

Hardiness	4 - 8
Exposure	Full Sun
Seasons	Summer (Early, Mid, Late)
Height	2' - 3' (60cm - 90cm)
Spread	1' - 2' (30cm - 60cm)

Eryngium planum ‘Blue Hobbit’ (Sea Holly)

Noted for its petite size, Eryngium planum ‘Blue Hobbit’ (Sea Holly) is a compact perennial boasting a profusion of spiny, egg-shaped, purplish-blue flower heads throughout the summer. They are produced on silver-blue stems and stand high above the basal rosette of deeply toothed, smooth textured leaves.

Hardiness	4 - 8
Exposure	Full Sun
Seasons	Summer (Early, Mid, Late)
Height	8" - 1' (20cm - 30cm)
Spread	6" - 1' (15cm - 30cm)

Eryngium planum ‘White Glitter’ (Flat Sea Holly)

Adding stature to the perennial garden, Eryngium Planum ‘White Glitter’ (Flat Sea Holly) is an elegant perennial with a profusion of glistening silvery ivory flowers, tightly packed into egg-shaped heads, that light up the garden throughout summer. They are produced on silver-green stems and stand high above the basal rosette of deeply toothed, smooth textured leaves.

Hardiness	4 - 8
Exposure	Full Sun
Seasons	Summer (Early, Mid, Late)
Height	2' - 3' (60cm - 90cm)
Spread	1' - 2' (30cm - 60cm)

Garden Design with Eryngium planum

When designing a garden with Eryngium planum, consider its unique characteristics and visual appeal. Here are some design ideas:

Color Contrast: Pair the steel-blue flowers of Eryngium planum with complementary colors like yellow or orange to create an eye-catching contrast in your garden.
Texture and Form: Take advantage of the spiky foliage and architectural form by planting it alongside plants with contrasting textures, such as feathery grasses or soft, rounded flowers.
Pollinator Gardens: Incorporate Eryngium planum into pollinator-friendly gardens, as its nectar-rich flowers attract bees, butterflies, and other beneficial insects.
Cottage Gardens: Eryngium planum’s cottage garden charm makes it a perfect addition to informal garden styles. Pair it with other cottage garden favorites like roses, daisies, and lavender for a romantic and whimsical look.
Wildlife Gardens: Create a wildlife-friendly garden by including Eryngium planum as part of a diverse plant selection that attracts birds, bees, and butterflies. Consider adding native grasses and flowering plants to enhance the habitat.
Cut Flower Gardens: Eryngium planum’s long-lasting flowers make it an excellent choice for cut flower arrangements. Include it in your cutting garden to add unique texture and color to your bouquets.
Rock Gardens: Eryngium planum’s compact size and ability to thrive in well-drained soil make it a great choice for rock gardens. Plant it among other low-growing perennials and ornamental grasses for a stunning display.
Mediterranean-Inspired Gardens: Eryngium planum’s drought tolerance and silver-blue color make it a natural fit for Mediterranean-inspired gardens. Combine it with lavender, rosemary, and other drought-tolerant plants for a low-maintenance and water-wise design.

Remember to consider Eryngium planum’s height, growth habit, and blooming season when planning its placement in your garden. With its unique beauty and versatility, Eryngium planum can add visual interest and charm to a variety of garden styles.

Companion Plants for your Flat Sea Holly

Stachys byzantina (Lamb’s Ears)

Panicum virgatum (Switch Grass)

Calamagrostis x acutiflora ‘Karl Foerster’ (Feather Reed Grass)

Rudbeckia hirta (Black-Eyed Susan)

Echinacea (Coneflower)

Sedum (Stonecrop)

Lavandula angustifolia (English Lavender)

Salvia (Sage)

Achillea (Yarrow)

Growing Tips

Eryngium planum is a popular and attractive plant that’s relatively easy to grow if you provide the right conditions. Here are some general steps to help you grow Eryngium planum:

Choosing a Location: Eryngium planum prefers full sun exposure, and it needs well-draining soil. It can tolerate a range of soil types, including chalky, loamy, and sandy soils.
Planting: You can start Eryngium planum from seeds or buy young plants. If starting from seed, sow them in a cold frame or directly outdoors in fall or spring. If you’re planting a young plant, dig a hole twice the diameter of the plant’s container, and place the plant in the hole so the top of the root ball is level with the soil surface. Backfill the hole and gently firm the soil around the plant’s base.
Avoid planting this plant in moist and fertile soils, where it will tend to sprawl and may require support.
The plant transplants poorly and is best left undisturbed once established.
Watering: Water the plants well after planting and regularly during dry periods. Once established, Eryngium planum is quite drought-tolerant and will need less frequent watering.
Feeding: Eryngium planum doesn’t require a lot of feeding.
Maintenance: Deadhead the flowers to prevent self-seeding (although the seed heads can provide winter interest and food for birds). Cut back the old stems and foliage in late winter or early spring before new growth begins.
Pests and Diseases: Eryngium planum is generally pest-free and disease-resistant. However, keep an eye out for aphids and root rot in poorly drained soils.

Remember, Eryngium planum is a perennial, so it will come back year after year. It can also self-seed readily (without being invasive), so be prepared for volunteer seedlings if you don’t deadhead the flowers.

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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.