In the diverse world of flowering perennials, the Eryngium, commonly known as Sea Holly, stands out as a truly unique and captivating addition to any garden. This extraordinary plant is not only a visual delight but also offers robust versatility in various garden settings. With its striking metallic hues, architectural form, and spiky, thistle-like blooms, the Sea Holly can transform a garden into a scene straight out of a fairytale.
I have Eryngium growing on-mass alongside Miscanthus ‘Morning Light’ and Verbena Bonariensis, and it looks simply fabulous.
Over the next five minutes, we’ll delve into the world of Eryngium, exploring its fascinating characteristics, how to grow it successfully in your garden, and why it’s a must-have for any gardener looking to introduce a touch of the unusual to their plant collection.
Don’t forget…
I’ve got a whole other article on the Top 9 Unusual Perennials to grow in your garden!
What Makes Eryngium So Unique?
Eryngium, or Sea Holly, is a genus of over 200 species of flowering plants in the Apiaceae family. Native to Europe, the Mediterranean, and parts of the Americas, this perennial is known for its remarkable appearance. The plant’s leaves are often spiny and stiff, resembling those of a holly bush, which is how it earned the name “Sea Holly.” However, the real showstopper is the flower itself.
Striking Appearance
The Eryngium flower is a spiky, cone-shaped bloom surrounded by a ruff of bracts that range in color from silvery blue to deep violet. The metallic sheen of the flower heads is particularly eye-catching, making them a focal point in any garden. Some species, like Eryngium giganteum, even boast a stunning silver hue, which can add an ethereal glow to your garden, especially in the early morning or late afternoon light.
Diverse Varieties
There are several varieties of Eryngium to choose from, each offering something slightly different in terms of size, color, and growth habit. Some popular species include:
- Eryngium alpinum (Alpine Sea Holly): Known for its intense blue flowers and deeply cut bracts.
- Eryngium giganteum (Miss Willmott’s Ghost): A towering variety with silvery-white flowers, named after the famous horticulturist Ellen Willmott.
- Eryngium planum (Flat Sea Holly): A compact species with small, bright blue flowers, perfect for smaller garden spaces.
Low-Maintenance Beauty
One of the many reasons gardeners love Eryngium is its low-maintenance nature. Once established, these plants require minimal care, making them ideal for both experienced gardeners and novices alike. Their drought tolerance and preference for poor, well-drained soils mean they thrive where many other plants might struggle.
Growing Eryngium in Your Garden
If you’re intrigued by the idea of adding Eryngium to your garden, you’re in for a treat. Not only does this plant bring a unique aesthetic to your outdoor space, but it’s also relatively easy to grow, provided you follow some key guidelines.
Choosing the Right Location
Eryngium thrives in full sun and well-drained soil. When selecting a location in your garden, choose a spot that receives at least six hours of direct sunlight each day. These plants are particularly well-suited to rock gardens, coastal gardens, and other areas with poor, sandy, or gravelly soil.
Soil Requirements
The Sea Holly prefers soil that is low in nutrients, which is another reason it’s such a great choice for challenging garden spots. Rich, fertile soil can actually hinder its growth, leading to weak, leggy plants. If your garden soil is too rich, consider amending it with sand or gravel to improve drainage and reduce nutrient levels.
Planting Eryngium
Eryngium can be grown from seeds, but the easiest way to introduce it to your garden is by purchasing young plants from a nursery. Plant them in the spring, after the danger of frost has passed. When planting, space the plants about 18 to 24 inches apart to allow for their mature size and to ensure good air circulation.
Watering
One of the great advantages of Eryngium is its drought tolerance. Once established, these plants require very little water, making them perfect for xeriscaping or low-water gardens. However, it’s important to water them regularly during the first growing season to help establish a strong root system. After that, you can reduce watering significantly, only giving them an occasional drink during prolonged dry spells.
Fertilization
As mentioned earlier, Eryngium prefers poor soil, so there’s no need to fertilize. In fact, feeding these plants can do more harm than good by encouraging excessive leaf growth at the expense of flowers. Let them thrive on the natural nutrients in the soil, and they will reward you with abundant blooms.
Pruning and Deadheading
Eryngium requires very little pruning. Simply remove any dead or damaged leaves in the spring as new growth begins. Deadheading, or removing spent flowers, can encourage the plant to produce more blooms throughout the season. However, if you enjoy the look of dried flowers, you can leave the spent blooms on the plant, where they will provide interest in the winter garden.
Winter Care
Eryngium is generally hardy and can withstand cold winters, especially if grown in well-drained soil. However, in regions with very harsh winters, it’s a good idea to apply a layer of mulch around the base of the plant in late fall to protect the roots from freezing. In the spring, remove the mulch to allow the soil to warm up and encourage new growth.
Companion Plants and Garden Design
Eryngium is a versatile plant that can be incorporated into a variety of garden designs. Its unique appearance makes it an excellent choice for adding texture and contrast to your garden.
Pairing with Other Plants
TEryngium, with its bold, spiky, almost futuristic look, works beautifully alongside softer, more delicate plants. This unexpected pairing creates the perfect balance in the garden. Whether you’re after a modern, structured vibe or a wild, meadow-like feel, Eryngium can be the star of the show while still playing nicely with others. Let me share some of my favorite companion plants for Eryngium, ones that I’ve seen transform gardens time and again.
Softening the Edges with Ornamental Grasses
One of the best plants to pair with Eryngium is ornamental grasses. The light, wispy movement of grasses creates a gorgeous contrast to the rigid, spiky form of Eryngium. Think of it like adding a soft blanket to a room full of sharp edges—it’s all about balance. I’ve planted Eryngium alongside Stipa tenuissima (Mexican Feather Grass) in a few designs, and it’s always a winner. The delicate, feathery grasses sway in the breeze while the Eryngium stands firm, creating a stunning visual dynamic that’s hard to beat.
I’ve also paired Eryngium with Miscanthus sinensis ‘Morning Light’ and Festuca glauca (Blue Fescue). The cool blue-green tones of Festuca really complement the silvery-blue hue of Eryngium, making for a calming, harmonious color palette. Plus, the different textures—the spiky sea holly and the soft, flowing grasses—make both plants stand out even more.
- Tip: Ornamental grasses and Eryngium are a dream team for low-maintenance gardens. Both are drought-tolerant once established and can thrive in the toughest spots where other plants might struggle.
Adding Pops of Color with Bright Perennials
Looking to liven up your garden? Eryngium pairs beautifully with vibrant perennials. One of my favorite combinations is with Lavender. The soft purple flowers of lavender look stunning next to Eryngium’s silvery-blue spikes. This creates a cool, serene effect in your garden. Both plants thrive in full sun and well-drained soil, making them a perfect match in terms of care.
For more contrast, pair Eryngium with Echinacea purpurea (Coneflower). The bold pink and purple flowers of Echinacea create a striking contrast with the metallic tones of Eryngium. Together, they form a showstopper in any garden. Both are also excellent for attracting pollinators like bees.
Shasta Daisies (Leucanthemum x superbum) are another great option. The white petals and yellow centers of the daisies provide a clean backdrop. This allows Eryngium’s bold form to really stand out. Combined, they offer a cottage garden charm with a modern twist. For more texture, consider adding Achillea (Yarrow). The flat-topped flowers of Yarrow contrast beautifully with the spiky heads of Eryngium.
Tip: When planting colorful perennials like Echinacea or Shasta Daisies with Eryngium, use odd numbers. Grouping in threes or fives creates a more natural flow and keeps your garden looking relaxed.
Creating Height and Layers with Taller Plants
For added drama, pair Eryngium with taller plants. Verbena bonariensis is a great choice. Its tall, airy stems topped with clusters of small purple flowers float gracefully above Eryngium. This combination adds softness without overpowering the Eryngium, creating depth and dimension.
Delphinium elatum (Delphinium) also pairs beautifully with Eryngium. The tall, elegant spires of Delphiniums in shades of blue, purple, or white make the perfect backdrop to Eryngium’s spiky blooms. This combination works wonderfully in mixed borders. The variation in height keeps things interesting and draws the eye upward.
Tip: Don’t be afraid to mix heights. Eryngium holds its own against taller plants, adding contrast and creating beautiful layers in your garden.
Making a Statement with Mass Plantings
For a bolder, more dramatic effect, try planting Eryngium in drifts or larger groups. When planted en masse, Eryngium’s spiky blooms and metallic hues make a huge impact, especially when the sun catches them just right. I’ve used this technique in several designs where I wanted to create a focal point, and the results were always stunning.
If you’re going for a naturalistic, meadow-like feel, try mixing large groups of Eryngium with Nepeta (Catmint), Salvia nemorosa, and Gaura (Whirling Butterflies). The soft, airy blooms of Nepeta and Gaura provide the perfect foil to the bold structure of Eryngium, while Salvia adds another layer of color and texture. This combination creates a garden that feels relaxed, almost like it’s evolved naturally, but with plenty of visual interest.
- Tip: Plant Eryngium in a spot that gets plenty of sunlight. The metallic blooms love to catch the light, and you’ll get the best show when they’re bathed in sun for most of the day.
Eryngium is one of those plants that can adapt to a variety of garden styles and still manage to stand out. Whether you’re aiming for a modern, minimalist look or a more wild, naturalistic garden, this striking perennial can serve as both a focal point and a team player. Pair it with soft grasses, bright perennials, or tall, dramatic plants, and you’ll have a garden that’s full of life, texture, and color—all while being relatively low-maintenance.
Using Eryngium in Floral Arrangements
Eryngium is not only a star in the garden but also makes a stunning addition to floral arrangements. The flowers, both fresh and dried, add texture and interest to bouquets. When cutting Eryngium for arrangements, be sure to wear gloves, as the spiny leaves and stems can be prickly.
To dry Eryngium flowers, simply cut the stems when the blooms are fully open and hang them upside down in a cool, dry place. Dried Eryngium flowers retain their color and shape well, making them perfect for long-lasting arrangements and wreaths.
Attracting Wildlife
In addition to its ornamental value, Eryngium is also a magnet for pollinators. The flowers are rich in nectar, attracting bees, butterflies, and other beneficial insects to your garden. This makes Eryngium an excellent choice for gardeners who want to support local wildlife and contribute to a healthy ecosystem.
By planting Eryngium, you’re not just adding beauty to your garden; you’re also helping to sustain the vital pollinator populations that many other plants rely on. In fact, some species of bees are particularly attracted to Eryngium, making it a valuable addition to a pollinator-friendly garden.
Troubleshooting Common Issues
While Eryngium is generally a low-maintenance plant, it can occasionally encounter problems. Here are some common issues and how to address them:
Poor Drainage
Eryngium does not tolerate wet, poorly drained soil. If you notice the plant’s leaves turning yellow and wilting, it may be suffering from root rot due to waterlogged soil. To remedy this, ensure your plant is situated in well-drained soil or consider amending the soil with sand or gravel to improve drainage.
Pests and Diseases
Eryngium is relatively resistant to pests and diseases. However, like many garden plants, it can occasionally be affected by aphids or powdery mildew. To control aphids, spray the plant with a strong jet of water to dislodge the insects or use insecticidal soap if the infestation is severe. Powdery mildew can be prevented by ensuring good air circulation around the plant and avoiding overhead watering.
Leggy Growth
If your Eryngium becomes leggy or floppy, it may be due to overly rich soil or insufficient sunlight. Ensure your plant is receiving full sun and consider moving it to a location with poorer soil if necessary.
Why Eryngium Should Be in Your Garden
Eryngium, with its striking metallic flowers, architectural form, and low-maintenance nature, is a standout addition to any garden. Whether you’re looking to add texture and contrast to your flower beds, attract pollinators, or simply enjoy the unique beauty of this unusual perennial, the Sea Holly is a plant that delivers on all fronts.
By following the tips outlined in this guide, you can successfully grow and enjoy Eryngium in your garden, creating a space that is not only beautiful but also brimming with life. So, if you’re ready to introduce a touch of the extraordinary to your garden, why not give Eryngium a try? With its enchanting blooms and easy-care requirements, it just might become one of your favorite perennials. If you need further expert guidance, check out this handy guide from Gardener’s World on growing unusual perennials.
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