Pyrenean sea holly

Sun

Full sun; shade reduces flowering and encourages weak stems.

Water

Water regularly during establishment, allowing the soil to dry between waterings. Established plants need extra water mainly during prolonged drought.

Soil

Well-drained, sandy, gritty or stony soil, preferably lean to moderately fertile. Tolerates neutral to alkaline soil; avoid heavy, wet ground.

Height

1.5-2.5 ft (0.45-0.75 m)

Spread

1-1.5 ft (0.3-0.45 m)

Flowers

Summer; small blue flowers in rounded heads surrounded by stiff, pointed, silvery-blue to violet-blue bracts.

Foliage

Deeply lobed, spiny green leaves with conspicuous pale or silvery-white veins.

Growth

Moderate; may take two growing seasons to establish well.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.3 ft (0.4 m)

3. After 2 years

   1.6 ft (0.5 m)

4. After 3 years

   2 ft (0.6 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Growth rate

Moderate

• Plant in a sunny, freely drained position; use a raised bed if your soil stays wet in winter.
• Water new plants through their first growing season, but do not keep the soil constantly moist.
• Avoid rich manure and routine feeding; excess fertility produces softer, floppier growth.
• Use a thin gravel mulch rather than moisture-retaining mulch around the crown.
• Choose its position carefully and avoid dividing or moving established plants, which have a deep taproot.

Pruning. Leave dry flower heads standing for autumn and winter structure, then cut dead stems to the base in late winter or early spring before new growth develops. Remove heads after flowering instead if you want to limit self-seeding.

Late winter

Cut down old stems before fresh growth appears, unless they have already collapsed.

Spring

Plant young plants after the soil becomes workable, keeping the crown at soil level.

Spring

Check emerging shoots for slugs and snails, and remove unwanted seedlings.

Summer

Water establishing plants during dry spells; leave established clumps fairly dry between waterings.

Late summer

Keep fading flower heads for structure, or remove them before seed drops.

Autumn

Clear fallen leaves away from the crown and check that water drains freely around it.

• Plant in gravel gardens with lavender and thyme for contrasting blue flowers and silver foliage.
• Repeat small groups through a sunny perennial border to give rhythm and sharply defined flower shapes.
• Combine with airy ornamental grasses so the rigid blue heads stand out against fine foliage.
• Use in raised beds or larger rock gardens where drainage is sharp and the patterned leaves can be seen closely.

Garden styles it suits: Dry gravel garden, Mediterranean, Cottage garden, New perennial (prairie), Pollinator garden and Desert / xeriscape.

Plant it with: English lavender, Catmint, Yarrow, Russian sage, Creeping thyme and Blue fescue.

Wildlife: The flowers attract bees, hoverflies and other nectar-feeding insects. Standing stems and seed heads add shelter and structure through winter.

• Crown and root rot in wet soil: improve drainage before planting, use raised beds on heavy ground, and keep damp mulch away from the crown.
• Slugs and snails eating new shoots: inspect young growth, remove pests by hand and use wildlife-conscious controls where needed.
• Weak or flopping stems: provide full sun, stop rich feeding and avoid excessive watering.
• Poor recovery after transplanting or division: plant young specimens in their permanent position and leave established taproots undisturbed.

Not known to be toxic to people, cats, dogs or horses, although species-specific information is limited. The sharp leaf and bract tips can prick skin and irritate mouths; it is not a food plant.

• Flat sea holly (Eryngium planum)

  Usually taller and more branched, with many smaller blue heads and mostly unlobed basal leaves lacking the strong white-veined pattern.

• Sea holly (Eryngium maritimum)

  Has broad, thick, waxy blue-grey leaves with shallow lobes rather than finely divided, strongly white-veined foliage; it naturally grows on coastal sand.

• Miss Willmott's ghost (Eryngium giganteum)

  Generally taller, with much larger silvery-white bracts and elongated flower heads; it is usually biennial or short-lived rather than a persistent clump-forming perennial.

The common name refers to its native occurrence in the Pyrenees and its holly-like, spiny foliage.

Propagation. Sow ripe seed in pots in autumn and leave outdoors in a sheltered position; winter cold can help germination, which may be slow and uneven. Named cultivars may not come true from seed and are better propagated by root cuttings during dormancy. Avoid dividing established clumps.

Accepted botanical name

Eryngium bourgatii

Native range

France, Morocco and Spain.

Measured

Soil pH 7.5 to 8.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.