Eryngium blue sea holly

Eryngium (Sea Holly)

Attractive, Sea Holly plants (Eryngium) are striking ornamental perennials grown for their arresting, thistle-like, silvery or blue tinted flower heads adorned with a ruff of showy bracts. Blooming in summer and sometimes into fall, they are useful in rock gardens, coastal gardens and in borders where their steel blue flowers and foliage complement the vibrantly colored summer flowers.

  • Their beautiful texture, unique color, long-lasting flowering and remarkable qualities as cut flowers make them a favorite of florists, gardeners, bees and butterflies. They are exceptionally care-free plants if they are given a well-chosen site.
  • With a trend toward drier summers, Eryngium has become even more popular. Easy to please, even in dry gardens where other border stalwarts suffer, Eryngium goes from strength to strength over the entire summer, complimenting every other plants with its silvery or metallic blue flower heads.
  • Drought tolerant, Sea Holly also handles salt spray with ease.

Eryngium maritimum

Eryngium alpinum

Eryngium planum ‘Blue Glitter’

  • Easy to grow, Eryngium prefers full sun – at least 6 hours of direct sunlight per day. The sunnier the site, the more intense the blue!
  • Eryngium prefers dry, poor to moderately fertile, well-drained soils with the exception of Eryngium pandanifolium (Giant Sea Holly) which prefers moist soils.
  • Most Sea Holly species are reliably perennial in Hardiness Zones 4 – 9. Exceptionally hardy, Eryngium alpinum is perennial in Zone 2. Eryngium amethystinum and Eryngium yuccifolium are perennial in Zones 3. Not sure about your growing zone? Check here.
  • Eryngium needs winter protection and a warm site in order to allow the rosettes to overwinter successfully, otherwise these plants use up all their energy replacing foliage.
  • Eryngium is a taprooted plant that transplants poorly and is best left undisturbed once established. Select your site carefully!

Eryngium alpinum ‘Blue Star’

Eryngium planum ‘Blue Cap’

Eryngium x zabelli ‘Jos Eijking’

  • Eryngium plants are relatively care-free once established.
  • Sea Holly plants do not require much watering except during long periods of drought.
  • Sea Holly plants do not require fertilization either. They may sprawl if grown in overly fertile soils.
  • Deadheading will promote additional blooming.
  • Sea Holly is popular with bees and butterflies, but not with deer and rabbits.

Eryngium x zabelii ‘Neptune’s Gold’

Eryngium giganteum

Eryngium pandanifolium

  • Eryngium combines beautifully with many companion plants, including Verbena bonariensis (Tall Verbena), Perovskia atriplicifolia (Russian Sage), Aconitum carmichaelii ‘Arendsii’ (Monkshood) or the glorious Echinacea (Coneflower).
  • The blues and silvers blend well with most colors and create a bold statement with yellow and orange annuals or perennial plants such as Rudbeckia, Coreopsis, Zinnia, and Cosmos.
  • Eryngium looks great in combination with ornamental grasses, the pairing creating a strong textural contrast. Molinia caerulea (Moor Grass), Helictotrichon sempervirens (Blue Oat Grass), Stipa gigantea or Stipa tenuissima are good possibilities.

Donard Variety Sea Holly

Metallic blue flower heads are surrounded
by a spiky skirt of vibrant
purple bracts, and flowers are quite
long-lasting! Silver-veined foliage
transforms to white in the summer,
and is complemented by the unique
blooms from midsummer to fall.
Stems can be cut back after flowering,
but many gardeners choose
to leave the attractive seed heads
untouched. A favourite among butterflies.
Perfect for the backs of
borders and containers, Sea Holly is
also popular in bouquets and dried
arrangements. Highly tolerant of
heat and resistant to drought.
3-8 #1 plants Part Shade 12-24″ Midsummer to Fall
If our Spring shipping season is closed, your order will be shipped the following Spring.
Variety description courtesy of Breck’s

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Buy Flower, Vegetable and Plant Seeds from Chiltern Seeds

Germination Instructions

Sow under glass. Sow into moist well-drained seed compost, cover with a thin layer of soil. Cold stratify. Place seed container inside a plastic bag and place in the fridge at 4°C for 2-3 weeks. Remove from fridge and place in a cold frame or shady part of the garden. Keep covered with plastic or glass. Germination is irregular 5-90 days. As each seed germinates in turn transplant to its own 8cm pot. Plant out to final position as soon as possible. Seed may enter dormancy and not emerge until the following spring.

Growing Instructions

Prefers full sun in a light well-drained soil. Will tolerate very light shade. Plant into final position while the plant is young. The roots are often several feet long and do not like to be disturbed.

Cultivation Instructions

Flower stems may be cut back after flowering but the seedheads are attractive and could be left over winter. Cut flowers before fully open if you wish to dry them. Divide in early spring or autumn, be gentle, the plant does not like root disturbance. Protect from winter wetness.

When to Sow

MarM AprA MayM JunJ JulJ AugA SepS OctO NovN DecD JanJ FebF
  • Sow Under Cover/Plant Indoors
  • Flowers/Harvest


Eryngium planum
Flat Sea Holly
Culture guide
Perennial, first year flowering. Cutflower, large containers, perennial borders, attractive for bees and butterflies
Garden height:
37″ / 95 cm
Crop time:
6-7 months
Sow time:
December-March for fl wering plants from June-August. July-August for larger flowering plants in the following year
Sowing method:
December-March for fl wering plants from June-August. July-August for larger flowering plants in the following year
Germinate at 72-75 °F (22-24 °C) for 7-10 days under lights.
Sow in a well drained media and cover lightly.

Growing On:
Transplant into a well drained media with a pH of
5.5 to 6.5.
Grow on at 60-70 °F (15-21 °C) for perennial pot production.
For cut flower production warmer temperatures result in longer stem length. Temperatures near
75° (24 °C) yield long strong stems. Fertilize at
50-100 ppm nitrate nitrogen after initial transplant increasing to 100-150 ppm once plants are well established.
Use a well-drained, growing perennial substrate, pH: 6.0-7.5. Field: humus, sandy loamy soils with good drainage.
Grow at 15-18 °C or outdoors. In winter indoors frost free at 3-5 °C or outdoors.
Outdoor fleece cover needed. In spring the plants start to grow at 12-18 °C or outdoors at ambient conditions. Containers can be stored in cold storage and set up in intervals for forcing afterwards.
High fertilization levels are required.
“Information copied from the breeder.
Muller will not accept any liability for failure and/or damage as a consequence of incorrect and/or inexpert cultivation by or on behalf of the Buyer.”

Eryngium ‘Big blue’ Sea Holly, at home in the sun in containers and gardens

Eryngium ‘Big Blue’

Add a statement to your garden! Eryngium x zabelii ‘Big Blue’ (USPP#20636, PBR 28175) comes to Rozanne and Friends® from Myerscough College of Preston, in Lancashire, UK.

The electric-blue flower heads have 4-inch (10 cm) wide bracts and the striking color extends down onto spiky foliage and along flower stems. Makes larger, taller plants than Eryngium ‘Blue Sapphire’.

Commonly known as “Sea Holly”, this variety originates from its native costal home. The spiny leaves, flowers and bracts refer to similar spiny leaf features of the evergreen shrub, Holly. Plants within this genus thrive in dry, sunny locations. ‘Big Blue’ Sea Holly loves the sun, so much that when in shade its color dilutes.

In the garden, often the highlight of one’s home exterior, the ‘Big Blue’ Sea Holly is a great accent plant for middle border gardens. But, you don’t have to limit this variety to only the garden’s border, as is also an impressive display en masse. Beyond the garden, mixing ‘Big Blue’ Sea Holly with other perennials creates beautiful and novel containers. Plants are also useful for cut and dried flowers, are attractive to butterflies and have a long bloom period in summer.

For Growers

  • Typically plant 1 liner per 4.5-inch (11 cm), 6-inch (15 cm) or 1-gallon (4 litre) pots.
  • Vernalization is required and plants need extra time to size up before overwintering. Plant in late summer to early fall and allow plants to bulk before vernalization. Overwinter outdoors or inside cold greenhouses. Allow plants to emerge and flower with naturally occurring spring temperatures. This method provides larger plants, more uniformity and more flowers.
  • Alternatively, plant vernalized liners in March and April. However, plants will not be as uniform, full or floriferous as in bulked, overwintered crops.
  • Standard media pH: 5.5 to 6.5; standard media EC 1.5 to 3 mmhos/cm.
  • Water thoroughly but allow to dry slightly between irrigations.
  • Primary problem can be root rot.
  • See our Technical Guide for more information.

In the garden

  • For middle garden borders accent plants or as massed plantings. Also, nice novelty plant for containers.
  • Plants are useful for cut and dried flowers, are attractive to bees and butterflies and have a long bloom period in summer.
  • USDA Hardiness Zone: 5 to 9.
  • Grow in full sun.
  • Spread 26 inches (66 cm).
  • Height 33 inches (84 cm).
  • Prefers well-drained garden soils.

Getting to know the Must Have Perennials™ – The plants your garden would choose™

Sea Holly Plant Care: How To Grow A Sea Holly Plant

Looking for a fascinating addition to the garden? Then why not consider growing sea holly flowers (Eryngium). Sea hollies can provide unique interest with their spiny-toothed leaves and clusters of teasel-like blossoms. They also offer versatility with their wide range of growing conditions and various uses in the garden.

What is Sea Holly?

Eryngium plants, also known as sea holly flowers, make striking additions to the garden. Mostly native to Europe and the Mediterranean, these plants generally grow anywhere from 18 to 36 inches (45-90 cm.) tall with a one foot (30 cm.) spread. Their green or silvery-blue stems give way to green or blue cones surrounded by spiky silver, white, green, blue or violet bracts, which bloom from summer throughout fall.

Sea holly plants are tolerant of drought, winds, salt sprays and sandy soils. They can be used as specimen plantings, in beds and borders, or butterfly gardens. In addition, these plants make excellent dried flowers.

Types of Sea Holly Flowers

Several species of Eryngium have been cultivated as garden plants and are widely available in most nurseries. Some of the most common sea holly plants include:

  • Alpine Sea Holly (E. alpinum) – Native to alpine pastures of Switzerland, both the flowers and stems of this species are considered the bluest of the genus. Growing about 2 feet (60 cm.) high, you’ll find this one at its peak during July and August.
  • Amethyst Sea Holly (E. amethystinum) – Growing 1-1½ feet (45 cm.) tall, this European native is one of the most cold hardy of the genus. It has beautiful amethyst blue flowers and a somewhat straggling nature.
  • Mediterranean Sea Holly (E. bourgatii) – Native to Pyrenees, this variety reaches 1-2 feet (30-60 cm.) and consists of lively blue-green flowers with silver bracts and white veins within its coarse, spiny leaves.
  • Giant Sea Holly (E. giganteum) – Also known as Miss Wilmot’s Ghost (named for English gardener Ellen Wilmot), this Caucasus native makes an excellent plant for grouping in a background, growing from 3 to 4 feet (90-120 cm.) or higher. While it may require staking, its heart-shaped leaves and large flowers are worth the extra effort.
  • Flat Sea Holly (E. planum) – Another plant with heart-shaped basal leaves, this native to Eastern Europe grows 2-3 feet (60-90 cm.) tall and produces numerous silver-blue flower heads.
  • Rattlesnake Master (E. yuccifolium) – A native to the eastern United States with creamy chartreuse, button-like flowers and strap-like leaves, this species reaches 2 to 4 feet (60-120 cm.) tall. Its name is said to derive from the myth that these plants could cure rattlesnake bites or drive them away.
  • Common Sea Holly (E. maritimum) – This plant is one of the smallest, growing from 6 inches to 1 1/2 feet (15-45 cm.) high.

How to Grow a Sea Holly

Growing Eryngium plants is easy. All types will thrive in full sun and moist soil with good drainage. In fact, they actually prefer sandy soil. The long taproot, however, allows the plant to tolerate poor soil conditions and drought.

Because of their taproot, locate sea hollies somewhere permanent, as they do not transplant easy. Place young plants in holes that are a few inches wider and deeper than their current root system.

Seeds can be sown directly in the garden, though they may not bloom the first year. The seeds require a warm moist stratification for one month followed by one month of cold moist stratification.

Sea Holly Plant Care

These plants are relatively care-free once established. Sea holly flowers do not require much in the way of watering except during long droughts.

It’s not necessary to fertilize sea holly either. Refraining from fertilization will keep the plants more compact and less droopy.

Deadheading should be part of your sea holly plant care. Pinch or cut off spent flowers to encourage additional blooming. You may also cut off the flower stems once its blooming period ends in autumn, but allow the evergreen leaves to remain.

Now that you know how to grow a sea holly, why not give this plant a try. It’s a great plant for difficult situations and ideal for attracting butterflies. As a bonus, when planted around your garden’s perimeter, it will help deter deer.

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