How to Plant, Grow and Care For Sea Holly

Strolling by a backyard with sea holly rising in it’s almost unimaginable with out stopping to test it out. These vegetation are so fascinating and delightful. With their hanging shades of blue and long-lasting distinctive flowers, it’s simple to think about why they maintain a particular place within the solar gardener’s coronary heart. 

Sea holly affords long-lasting magnificence and is nearly too simple to look after. This plant thrives in these sunny areas in your backyard the place nothing will develop.

Surviving the most popular and driest areas of our yard, it is going to be the star of your mid-summer backyard. Let’s dig in and be taught what we have to develop and look after this perennial flower.

Sea Holly Overview

Plant Sort

Herbaceous Perennial

Soil pH

Acidic, Impartial, Alkaline

Native Areas

Europe, China

Bloom Time

Summer time and Fall

Flower Shade

Blue, Purple


Powdery Mildew, Leaf Spot


Aphids, Slugs, Snails

Plant Historical past 

Close-up of a flowering Sea Holly plant against a blurred garden background. The plant consists of upright purple stems with lobed blue leaves. The flowers are made up of protruding cones made up of tiny purple flowers. The cones are surrounded by spiky silver-blue bracts.
This carrot household plant has deep faucet roots, traditionally used for drugs and meals.

The flat sea holly, additionally recognized botanically as Eryngium planum, is a member of the carrot household. It produces a faucet root just like that of a carrot, rising deep into the bottom in quest of water, vitamins, and stability. 

The ocean holly is native to areas of Europe and Central China. Crops of the Eryngium genus have been traditionally used as natural cures to deal with numerous totally different illnesses. The lengthy taproots was eaten the best way we eat root greens, like carrots and potatoes, as we speak. 

The plant has additionally gained reputation for its magnificence and straightforward cultivation. Sea holly has been hybridized, and many sorts can be found for gardeners to get pleasure from. It is usually a favourite of florists. The flowering stems can last as long as two weeks and dry fantastically. 


Close-up of a Sea Holly (Eryngium) flowering plant against a blurred background of green. This perennial plant has a hard and strong stem that has a bluish color. The stem is branched and has a prickly structure. The leaves are lobed, silvery in color. The flower heads are spherical and consist of clusters of smaller cone-shaped structures surrounded by spiky blue-gray bracts.
Many Eryngium varieties showcase variations in showiness, bract measurement, and flower cone dimensions.

Except for the favored flat sea holly, there are different sorts of Eryngium. Beneath are only a few:

  • Eryngium alpinium (Alpine sea holly)
  • E. amethystinum (Amethyst sea holly)
  • E. bourgatii (Mediterranean sea holly)
  • E. maritimum (sea holly)
  • E. pandanifolium (Large sea holly)

Every of those varieties loves the complete solar and can develop 1-3 toes tall and 1-5 toes extensive. The mid-summer to fall blooms all resemble one another, though some are a bit extra frilly than others, whereas others might have broader bracts or bigger flower cones. 


These vegetation might be propagated by taking root cuttings or rising from seed. 

Root Cuttings

Close-up of three cuttings of Eryngium on a white background. The cuttings have thin green-purple stems and flower heads. The flower heads are cone-shaped, consisting of small green-blue flowers surrounded by spiky green bracts.
Taking root cuttings might be difficult however rewarding.

Root cuttings are somewhat difficult to do because it requires that the plant is dormant. In case your sea holly isn’t dormant, don’t attempt to propagate by root division! Nonetheless, root cuttings guarantee your plant is a clone of its father or mother plant, and is good for propagating particular cultivars in true kind.

Start by gathering the required gear. You’ll want some pots of pre-dampened potting combine, a trowel to dig up your father or mother plant, and clear, sterile snips or pruning shears. Some rooting hormone is beneficial however isn’t completely required.

Dig up the dormant plant and rinse filth off the roots to reveal all of them. Study the roots intently, deciding on a couple of wholesome ones which can be across the diameter of a pencil. You shouldn’t lower off greater than 1/third of the plant’s root system when doing this methodology, and you’ll want to work rapidly to forestall injury to the roots.

Along with your snips, lower your chosen pencil-diameter roots off cleanly and instantly replant the father or mother plant. This, paired with the plant’s dormancy, ought to scale back the dangers of shock to the plant’s remaining root system.

Now look at your roots. For this course of, you’ll want to chop roughly 3″ lengths of root. Trim the primary root to a flat lower, then lower a 3″ section off at an angle. If utilizing rooting hormone, instantly roll this within the hormone, then set it right into a pot with the angled lower pointed down. Cowl the basis solely, preserving the flat-cut high just under the soil’s floor.

Repeat the method with the remaining root segments, reducing them flat on the highest, measuring a 3″ section, then doing an angled lower and planting it instantly (with root hormone if utilizing). Plant the underside of the basis reducing with out trimming off the underside if it’s nonetheless thick sufficient to make use of.

Maintain the soil damp however not soggy, and defend your potted roots over the winter. Within the spring, you must see new shoots creating from the basis cuttings.


Close-up of a dry Eryngium flower head in a sunny garden, against a blurred blue-gray background. The flower head forms a dry cone which is the seed pod. The flower cone is surrounded by spiky dry bracts.
Collect mature seed heads in a bag within the fall and refrigerate over winter for spring planting, or instantly resow.

You possibly can develop this perennial from seeds bought at your native backyard middle or acquire seeds out of your current vegetation. 

Within the fall, clip off your mature (and brown) seed heads and acquire them in a paper bag. This may enable the seeds to fall off naturally and maintain them multi functional place for you. As soon as the seeds have come free, place the brown paper bag within the fridge for the winter months if you happen to plan to sow them within the spring. Alternatively, do a fall-sowing of your seeds so they arrive up within the spring. 

Methods to Plant

There are two frequent methods to plant sea holly. The primary is by seed, and the second is by planting a plant bought from a backyard middle or nursery. 


Close-up of Eryngium seedlings in blue colored plastic pots. The seedling forms a rosette of thick stems with oval, strongly serrated leaves of a pale green color. Oval lobed leaves with sharp tips grow in the center of the rosette.
Ensure your planting gap is deep sufficient to maintain the taproots straight.

It’s possible you’ll buy bare-root vegetation or potted vegetation out of your native nursery. You may additionally have began from seed indoors! Let’s speak about easy methods to plant them out.

Naked-root sea holly vegetation are unusual, however they do exist. Once you carry dwelling a bare-root plant, take away it from the packing materials it’s in (normally damp wooden chips) and place it in a container of water. Whereas it’s soaking, dig a gap that’s a minimum of 2x the width and the required depth for the basis ball.

Gently place your plant into the outlet when you’ve ready it, guaranteeing the faucet root is as straight as attainable – don’t bunch up the roots to suit the outlet! Backfill with backyard soil and water.

For those who’re planting your individual begin or a nursery plant that’s in soil, rigorously take away it from its pot and gently untangle any roots which have began to circle. Once more, plant it in such a means as to maintain its taproot straight down for finest development and backfill along with your backyard soil to the identical depth it was planted in its pot.

Sea hollies don’t like a whole lot of water, however they are going to want some assist getting established. Maintain your eye on the plant and the soil it’s rising in. Maintain it moist by evenly watering it as wanted. 


Close-up of a young sprout of Eryngium in a dark green plastic pot. The seedling forms oval light green leaves with serrated edges.
For higher outcomes, straight sow seeds within the fall for chilly stratification.

You might have two selections to plant from seed: begin your seeds indoors or straight sow them into the bottom.

For seeds began indoors: Seeds must be planted indoors 10-12 weeks earlier than your common final frost. Earlier than planting, you must maintain your seeds within the fridge for a minimum of 2-3 months. Enable the seeds to come back to room temperature earlier than gently urgent them into the potting combine, however don’t cowl the seeds with soil. Maintain the soil evenly moist. After they have germinated and have reached a couple of inches tall, harden your vegetation off to the outside situations after which transplant them exterior.

For seeds direct-sown outside: Your seeds must be planted within the fall. Put together your planting location and press the seeds firmly towards the soil’s floor. Don’t cowl with soil, and maintain the soil moist.

These vegetation require vernalization or publicity to chilly temperatures – with out it, they won’t germinate. As well as, sea holly requires mild to germinate within the spring, so press these seeds firmly onto the soil’s floor however don’t cowl them!

Sea holly is sluggish to germinate. Whereas if the situations are excellent, it’ll pop up inside per week or two, it could possibly stall for so long as 90 days earlier than popping up. Be affected person!

Methods to Develop

Now that you’ve a cheerful plant rising in your backyard, let’s discover look after these perennials. 


Close-up of Sea Holly (Eryngium) flowering plants in a sunny garden against a blurred background. The plant has many upright branched stems that are silvery purple in color. At the tops of the stems, cone-shaped inflorescences of small blue-green flowers are formed, surrounded by spiky silver-blue bracts.
For thriving vegetation, present 8 hours of full solar each day.

You’ll have essentially the most profitable sea holly vegetation in the event that they obtain 8 hours of direct solar every day. These perennials are tolerant of somewhat shade, however this may occasionally lead to weaker vegetation that will droop or flop below the burden of the flowers. 


Top view, close-up of a Sea Holly (Eryngium) flower in a garden, covered with water drops. The flower head is cone-shaped and consists of tiny blue flowers. The cones are surrounded by pointed, elongated blue bracts.
The deep taproot makes it drought-tolerant as soon as it’s established.

Sea holly produces a really lengthy taproot. This taproot permits the perennial to be fairly drought-tolerant. As soon as your perennial is established in your backyard, chances are you’ll not have to water all of it besides throughout a really lengthy dry spell. Nonetheless, that doesn’t imply you must utterly skip watering. To provide flowers, it does want water!

Hand-watering must be executed on the base of the plant. This may forestall an excessive amount of moisture from amassing across the base of the plant. In case your soil retains an excessive amount of water, the plant’s crown can rot. 


Close-up of young Sea Holly (Eryngium) plants in the garden, with a layer of mulch. The plant forms dense oval leaves of light green color, with serrated edges. Mulch is dry straw.
This perennial thrives in sandy, well-drained soil, tolerating poor fertility, however be cautious of moist soil inflicting root rot.

This flower grows finest in soil that’s sandy and well-drained. It is usually very tolerant of poorly fertile soils. For those who develop it in soils that aren’t well-draining, chances are you’ll wrestle with root rot.

If the taproot sits in moist soil for too lengthy, it could possibly rot and die off, leaving the plant with out its important water and nutrient collector. 

Local weather and Temperature

Close-up of Sea Holly (Eryngium) flowering plants in a sunny garden against a blurred background. The stems are branched, blue-silver in color with spiky blue-green leaves. Flower heads form cones of small blue flowers surrounded by pointed blue-silvery bracts.
It’s sturdy in zones 4-9 and tolerates various climates, together with humidity, salt, and dryness.

Most species are hardy in zones 4-9. These vegetation are robust and resilient and shouldn’t have another local weather necessities so long as they’re planted inside their hardiness zones. Sea holly is tolerant of humidity, salt, and dry situations. 


Close-up of a flowering Sea Holly plant in a sunny garden. It forms strong, upright, silvery-purple, branched stems, with deeply divided, lobed, silvery-blue leaves. The flower heads are spherical and consist of a cluster of smaller, cone-shaped structures surrounded by a series of bracts resembling spiny petals.
Keep away from fertilizing these vegetation; they excel in poor soil, and extreme fertilizer can result in sprawling development.

There isn’t a have to fertilize this plant. These perennials thrive in poor soil. Including an excessive amount of fertilizer may cause them to sprawl. 


Close-up of a flowering Sea Holly plant against a blurred green background. The flower heads form cones with a dense cluster of small bright blue flowers surrounded by long, spiky blue bracts with sharp, serrated edges.
As soon as established, this perennial is low-maintenance. Merely get pleasure from its distinctive flowers.

Sea holly is a really low-maintenance plant. As soon as established, there really is little so that you can do aside from get pleasure from their distinctive flowers. 

Deadheading spent blossoms will assist to elongate the bloom time by selling the formation of latest flowering. Nonetheless, the flowers dry very properly whereas on the plant, including continued curiosity in your backyard properly into the autumn and winter. 

On the finish of the rising season, chances are you’ll lower your plant proper all the way down to the bottom. Just like deadheading, that is optionally available! The dried flowers can present one thing enjoyable to take a look at within the wintertime when the remainder of your backyard could also be barren.

Both means, it is very important give the rosettes of foliage some safety from the winter. You possibly can place leaves or evergreen needles on high. Then, the plant gained’t have to supply new foliage within the subsequent rising season. 


Take pleasure in an intriguing variety of spiky blooms by mix-and-matching your favourite varieties.

‘Blue Cap’

Close-up of a blooming Eryngium maritimum 'Blue Cap' against a blurred helena background. Flower bracts, stems and leaves are bright blue or bluish-green. Blue Cap has spiny leaves with deep lobes. The flower head is composed of cone-shaped structures surrounded by bracts that form a pointed cup-like structure.
With silver stems and vibrant blue bracts, ‘Blue Cap’ is a clump-forming plant excellent for borders or mass planting in sizzling perennial beds.
  • Hardiness Zone: 4-8
  • Plant Measurement: 2-3 toes tall, 1-2 toes extensive
  • Flower Shade: silver-blue

This beautiful selection produces silver stems which assist vibrant blue bracts. These blue bracts offset the silvery-blue cluster of egg-shaped flowers. Clump-forming ‘Blue Cap’ makes an ideal border plant for the entrance of your sizzling perennial beds. It additionally seems pretty planted in a mass by itself. 

‘Blue Glitter’

Close-up of a Sea Holly "Blue Glitter" against a blurred brown-green background. This plant has an intense blue color. The stems are blue with striking blue flower heads surrounded by spiky blue bracts. Flower heads consist of small blue flowers collected in a dense cone.
That is an enhanced selection with engaging blue-green leaves and silver stems.
  • Hardiness Zone: 4-8
  • Plant Measurement: 2-3 toes tall, 1-2 toes extensive
  • Flower Shade: silver-blue 

‘Blue Glitter’ is taken into account to be an improved selection. Packing the identical punch as the remainder of the group, ‘Blue Glitter’ matures a bit sooner and produces extra blossoms. The deeply toothed blue-green leaves are low-growing from strikingly silver stems. 

‘Blue Hobbit’

Close-up of a blooming sea holly Blue Hobbit plant in a sunny garden, against a blurred background. Both flower heads and foliage are shades of bluish green. The leaves have deep lobes and spines similar to those of other sea holly varieties. The lobed structure gives the leaves a textured appearance. The flower heads are made up of numerous small florets tightly packed together in a spherical shape. The flower heads are surrounded by spiky bracts that are blue-purple in color.
This compact selection is good for entrance beds, that includes purple-tinted flowers on sturdy silver-blue stems.
  • Hardiness Zone: 4-8
  • Plant Zone: 8 inches to 1 foot tall, 6 inches to 1 foot extensive
  • Flower Shade: purple-blue

‘Blue Hobbit’ is a miniature model of the ocean holly chances are you’ll be used to. This is a wonderful selection for the entrance of a flower mattress or perhaps a raised backyard mattress. The ‘Blue Hobbit’ flowers are somewhat extra purple than another varieties. They’re nonetheless borne on silver-blue stems and are very long-lasting. 

‘Metal Blue’

Close-up of Eryngium planum 'Steel Blue' against a blurred green background. The flower head consists of numerous tiny green inflorescences tightly fused together in a ball shape. The flower heads are surrounded by spiky petal-like bracts. The steel blue color of the bracts emphasizes the unique appearance of the plant.
‘Metal Blue’ is tall and nice for reducing gardens, with lengthy stems and traditional steel-blue flowers.
  • Hardiness Zone: 5-9
  • Plant Measurement: 2-4 toes tall, 1-2 toes extensive
  • Flower Shade: steel-blue

The ‘Metal Blue’ selection is a gorgeous choice in your reducing backyard. This selection grows somewhat bit taller than a number of the different varieties. The stems are lengthy and excellent in your vase preparations. This selection has traditional steel-blue flowers that may attain one inch in diameter. 

‘White Glitter’

Close-up of a blooming Eryngium planum 'White Glitter' against a blurred green background. It is a cultivated variety of holly known for its characteristic appearance with white or light-coloured elements. The leaves have deep lobes and spines and are pale green in color. The flower heads of 'White Glitter' consist of numerous tiny cream-colored flowers densely packed into a globular shape. The flower heads are surrounded by spiky bracts that are pale green in color.
The ‘White Glitter’ selection affords silvery white hues with inexperienced stems and ivory-colored flowers.
  • Hardiness Zone: 4-8
  • Plant Measurement: 2-3 toes tall, 1-2 toes extensive 
  • Flower Shade: Silver- White

If blue or purple doesn’t match into the colour scheme of your backyard, don’t sweat it. ‘White Glitter’ affords you all the things the blue varieties do however in a gorgeous silvery-white shade. The stems have a silvery-green hue which strongly helps the ivory egg-shaped flowers. 


Close-up of Eryngium plants affected by snails, in a sunny garden. The plant has cone-shaped dry inflorescences surrounded by pale green pointed bracts.
These flowers are usually insect-resistant attributable to their prickly look and pure habitat.

There aren’t too many bugs that may bug sea hollies. That is partly due to its prickly look. However it additionally has to do with the plant’s habitat. For those who develop it in an excessive amount of shade, chances are you’ll discover aphids, slugs, and snails inflicting points along with your plant’s decrease leaves. 

Planting in full solar will assist to maintain these bugs away. For those who run into points with slugs and snails, you may take away them by hand. I’m not up for that slimy job, so I’d simply head to my native backyard middle and purchase an natural slug or snail bait. 


Close-up of an Eryngium leaf affected by powdery mildew. The leaf is oval, dark green, with serrated edges. The leaf is covered with a white powdery coating.
Sea hollies thrive in disease-resistant situations, but moist settings might invite powdery mildew or leaf spot.

Because of the rising situations that these vegetation thrive in, they usually don’t run into hassle with any ailments. Nonetheless, if rising in a moist atmosphere, chances are you’ll discover fungal ailments similar to powdery mildew or leaf spot.

These fungal ailments might be handled with copper fungicides if wanted. One of the best ways to maintain ailments below management is to make sure every plant has ample airflow round it and maintain moisture off of the leaves. Moist leaves are extra vulnerable to airborne fungal spores turning into caught within the moisture.

Plant Makes use of

Close-up of flowering Eryngium plants against a blurred background of flowering yellow yarrows. Eryngium planum has erect, branched blue stems with deep, lobed silver-blue leaves. Flower heads consist of small purplish-blue flowers tightly clustered in cone-shaped inflorescences. The inflorescences are surrounded by spiky blue bracts.
This plant excels in sunny, poor-soil areas, good for mass planting or standalone use.

You probably have a blazing sunny spot in your backyard with poor soil, sea holly is the reply to all of your issues. This perennial thrives in these kind of situations.

Plant them in teams for a giant assertion, or use them alone to make a spunky assertion. You probably have a reducing backyard, this flower is a must have! These blooms make beautiful accents to your vases and bouquets. 

Ceaselessly Requested Questions

Sure! Because the flowers mature, they are going to produce seeds that relaxation throughout the bracts of the plant. These seeds might be taken off by the wind and can produce volunteer vegetation for you all through your backyard. If you do not need these vegetation to self-seed, merely deadhead the flowers as they start to fade. Deadheading may even encourage the manufacturing of extra flowers extending the bloom time.

It isn’t frequent to see this flower rising in containers. That is primarily due to the soil situations required by these perennials. One more reason is due to their taproot, which grows so lengthy that it will make it troublesome to maintain it rising fortunately in a container.

Nonetheless, it may be executed! Combine in some succulent potting soil alongside along with your different potting soil to maintain the roots good and dry. Be ready to re-pot this plant as wanted. This species doesn’t transplant simply, so maintain that in thoughts when you find yourself managing your expectations for this plant.

This species doesn’t prefer to be moved as soon as it has been established in your gardens. That is due to the lengthy faucet root that it produces. Make sure you choose an area in your backyard the place you may be completely satisfied to have this perennial for years to come back.

In case your sea holly is missing its usually silvery-blue colour examine how a lot water it’s recieving. Browning of foliage is probably going attributable to an excessive amount of humidity within the air or an excessive amount of moisture within the soil. There may be not a lot you are able to do concerning the humidity, sadly. However you may maintain off on watering and provides the soil a while to dry out.

Remaining Ideas 

Sea holly is the proper perennial you probably have a sizzling and sunny patch in your yard. These vegetation solely look sharp and scary. In actuality, they’re distinctive and delightful. With a couple of totally different varieties out there to you, you may choose the proper selection in your backyard. For such a low-maintenance plant, it provides a whole lot of magnificence to your sunny gardens.

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