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Sea holly

Eryngium maritimum · Apiaceae

The gardener's calendar

The right move for September

Ideal time to plant sea holly: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.

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ID card

Foliage
Evergreen, greyish and rigid
Flowering
July to September, blue-violet flowers in compact umbels
Adult size
40 to 60 cm tall, 30 to 40 cm spread
Growth
Slow and spreading
Hardiness
Down to −15 °C
Origin
Atlantic and Mediterranean coasts of Europe
Soil type
Sandy, well-drained, salt-tolerant
Exposure
Full sun essential

Care

Watering

Moderate and regular during establishment (first year). Once established, sea holly tolerates drought well and makes do with rainfall. Avoid stagnant moisture, which promotes root rot.

Exposure

Plant sea holly in full sun, ideally in a windy position. This plant loves intense light and dislikes shade. By the seaside, it benefits from salty air and sea spray.

Soil and drainage

Prefer sandy, poor and very well-drained soil. Organic amendment is not necessary and can even promote rot. Salt-tolerant, it adapts to coastal soils and chalky ground.

Fertilizer

No fertilizer required. This hardy plant of difficult environments thrives without excessive nutrients. Over-feeding encourages soft growth and reduces hardiness.

Pruning and maintenance

Remove spent flowers after flowering to promote a compact shape. Evergreen foliage cleans itself of natural drying. Little intervention is needed: this plant displays a naturally balanced habit.

Diseases and pests

Very robust in dry, sunny conditions. Excessive moisture sometimes causes root rot. Check drainage and reduce watering if in doubt. Little susceptible to common pests.

Did you know?

Sea holly was long valued in traditional medicine for its supposed diuretic and tonic properties. Its rigid leaves and steel-blue flowers inspired many botanical artists. This species now appears on protection lists across Europe, as it colonizes fragile coastal zones threatened by urbanization.

Where to buy it

Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.

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Tips generated and checked by Viridia — adapt them to your local climate.