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Key characteristics

Family: Apiaceae
Height: 30 to 40 inches
Width: 12 to 18 inches
Flower color: Bluish to purplish, forming globular heads
Foliage color: Gray-green with spiny margins
Bloom time: June to September
Light: Full sun
Water: Low to moderate
Maintenance: Low; minimal care required
Growing zone: USDA zones 3 to 9
Wildlife: Attracts bees and butterflies

Perennials

Eryngium planum

Flat Sea Holly

Eryngium planum, commonly known as flat sea holly, is a perennial native to regions including the Alps, Jura, and the Balkan mountains. In summer, it produces steel-blue, thistle-like flower heads atop branched stems, rising from a rosette of dark green, deeply toothed basal leaves.

This plant thrives in full sun and is drought-tolerant once established, making it suitable for dry, sandy, well-drained soils. Its unique texture and color provide lasting interest in the landscape, and it serves as a valuable addition to gardens, attracting bees and butterflies.

Light

Full sun

Water

Low to moderate

Bloom time

June to September

Find this plant

Works well in

Borders
Sun Gardens
Pollinator Gardens
Waterwise Gardens
Cut Flower Gardens

Companion plants

Ornamental grasses · Garden phlox · Black-eyed Susans · Daylilies · Lavender · Coreopsis

Design tip

Foliage and form do most of the work here, so lean on texture and repetition rather than one flowering moment. In full sun it holds its shape best, and grouping several together keeps the color strong enough to be seen from across the garden.

Printable plant sheet (PDF)