What hardiness zones is Eryngium Hybrids suitable for?

Eryngium Hybrids is suitable for USDA hardiness zones 4, 5, 6, 7, 8, 9.

What are the sun requirements for Eryngium Hybrids?

Eryngium Hybrids requires Full Sun.

How much water does Eryngium Hybrids need?

Eryngium Hybrids has Very Low water needs.

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Perennials

Eryngium Hybrids

sea holly

Apiaceae

Hybrid of garden origin; parent species from Europe and the Mediterranean

At a Glance

TypePerennial

HabitUpright

FoliageEvergreen

Height18-36 inches (45-90 cm)

Width18-24 inches (45-60 cm)

Maturity3 years

Growing Zones

USDA Hardiness Zones

4 - 9

Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9

These zones indicate the coldest temperatures this plant can typically survive.

What's my zone? →

Frost Tolerancehardy

Key Features

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant

Maintenancevery low

Overview

Eryngium hybrids are sea hollies, perennial plants growing 18-36 inches (45-90 cm) tall and 18-24 inches (45-60 cm) wide. Cone-shaped thistle-like steel blue to violet-blue flower heads 1-2 inches (2.5-5 cm) surrounded by spiny bracts in midsummer to early fall (July-September) — the metallic blue coloring extends from the flower heads down the stems and bracts. Green spiny-margined basal foliage. In the carrot family (Apiaceae) — despite the thistle-like appearance, not related to true thistles (Cirsium, Asteraceae). The genus Eryngium contains approximately 250 species worldwide. Commonly cultivated hybrids: 'Big Blue' (large heads, 30 inches / 75 cm), 'Sapphire Blue' (deep blue, compact), E. × zabelii 'Jos Eijking' (violet-blue, 24 inches / 60 cm). The dried flower heads persist through fall and winter. Deep taproot: do not transplant once established. Lean poor well-drained soil produces the most vivid blue coloring — rich moist soil reduces the metallic blue and produces green floppy growth. Tolerates alkaline and chalky soil (pH to 8.0). Non-toxic. Deer-resistant (spiny). Drought-tolerant once established. Full sun. Zones 4-9. This entry represents the hybrid group. Growth rate is moderate.

Native Range

Hybrid of garden origin. Parent species native to Europe and the Mediterranean.

Suggested Uses

Commonly planted in gravel gardens, dry borders, and mixed borders in zones 4-9. The metallic blue flower heads and the dried winter structure provide two-season interest. Lean soil for blue coloring. Non-toxic. Deer-resistant. This entry represents the hybrid group.

How to Identify

Identified by cone-shaped thistle-like flower heads with spiny bracts — the metallic steel blue to violet-blue coloring extends from flower heads down the stems. In the carrot family (Apiaceae), not related to true thistles. Deep taproot. Lean soil for vivid blue color. This entry represents the hybrid group.

Appearance

Size & Dimensions

Height1'6" - 3'

Width/Spread1'6" - 2'

Reaches mature size in approximately 3 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Summer

Midsummer to early fall (July-September), lasting 6-8 weeks. Steel blue to violet-blue cone-shaped flower heads with spiny bracts. Dried heads persist through winter. Pollinator nectar source.

Detailed Descriptions

Flower Description

Steel blue to violet-blue, cone-shaped thistle-like flower heads 1-2 inches (2.5-5 cm) surrounded by spiny bracts

Foliage Description

Green with spiny margins (basal); stems and upper bracts develop metallic steel-blue to violet-blue coloring in flower

Growing Conditions

Sun Requirements

Full Sun

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 8.0(Neutral)

357912

Soil Types

sand loam chalk rocky

Drainagewell drained

Water & Climate

Water Needs

Very Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Full sun. Lean poor well-drained soil for vivid blue — rich soil reduces the coloring. Tolerates alkaline and chalky soil (pH to 8.0). Deep taproot — do not transplant. Leave dried heads for winter structure. Cut to ground in early spring. Non-toxic. Deer-resistant (spiny). Drought-tolerant. Zones 4-9.

Pruning

Cut all stems to the ground in early spring (March) before new growth. Do not deadhead during the season — the dried flower heads are an ornamental feature. Do not transplant (deep taproot).

Pruning Schedule

early spring

Maintenance Level

very low

⚠️ Toxicity Warning

Non-toxic