Eryngium (Sea Holly)

Why Should I Grow Sea Holly?

Growing Sea Holly in your garden can provide a number of advantages:

Unique Aesthetics: Eryngium plants stand out with their spiky texture, distinctive thistle-like flowers, and sometimes blue or silvery tones. They can act as a focal point in your garden and draw the eye.

Attracts Pollinators: Sea Holly is an excellent plant for attracting pollinators. Its nectar-rich flowers are popular with a variety of beneficial insects, including bees and butterflies. This can help support local ecosystems and contribute to a biodiverse garden.

Drought-Tolerant: Eryngium is a very drought-tolerant plant, making it a great choice for gardeners in regions with hot, dry summers or for those who want low-maintenance plantings. It’s well-suited to xeriscaping.

Deer and Rabbit Resistant: Thanks to its prickly foliage and stems, Sea Holly is usually avoided by deer and rabbits. If these pests are a problem in your area, planting Eryngium can save you a lot of hassle.

Versatile: Sea Holly can be used in various types of gardens such as rock gardens, coastal gardens, cottage gardens, or perennial borders. Its resilient nature makes it adaptable to a range of conditions.

Floral Arrangements: Eryngium flowers are long-lasting and retain their shape and color well, even when dried. This makes them excellent for use in floral arrangements and crafts.

In short, if you’re looking for a plant that offers striking visual interest, is low maintenance, and attracts beneficial wildlife, then Eryngium would make an excellent choice.

Garden Design with Eryngium

Sea Holly can be a striking addition to various garden designs due to its unique color, texture, and structural form. Here are some ideas on how to integrate it into your garden design:

Focal Point: With their unique thistle-like flowers and often bluish or silver hues, Eryngium plants can act as a focal point in a garden bed or border. Their spiky form creates visual interest and can break up the soft forms of other plants.

Cottage and Coastal Gardens: Sea Holly is a traditional component of cottage gardens and also adapts well to coastal gardens due to its salt tolerance. Pair it with other cottage garden favorites like roses, delphiniums, or lavender for a classic look.

Rock Gardens: Because of their preference for well-drained soil, Eryngium varieties work well in rock gardens. Pair them with other drought-tolerant species like sedums, sempervivums, or small ornamental grasses.

Mixed Perennial Border: Use Sea Holly in a mixed border to provide contrast with softer or rounder flowers. It pairs beautifully with coneflowers, black-eyed susans, lavender, and ornamental grasses.

Wildlife Garden: If your aim is to attract and support wildlife, Eryngium is a great choice. Plant them with other nectar-rich plants to create a buffet for bees, butterflies, and other beneficial insects.

Modern and Architectural Gardens: Sea Holly’s structural form works well in contemporary, minimalist garden designs. Pair them with other architectural plants like agaves or tall grasses, or use them to add texture to a garden full of sleek, smooth-leaved plants.

Cutting Garden: Grow Eryngium in a cutting garden to provide unique, long-lasting flowers for bouquets and floral arrangements. They even retain their shape and color when dried, adding to their utility.

Remember that Eryngium, like all plants, will thrive best when its preferred growing conditions are met. Make sure to give it a sunny spot with well-drained soil to help it look its best.

Companion Plants

Sea Holly has a unique texture and color that can contrast beautifully with many different types of plants. Here are some suggestions for companion plants:

Ornamental Grasses: The spiky form of Eryngium contrasts well with the flowing, feathery forms of ornamental grasses. Try Panicum, Stipa, or Miscanthus for an interesting textural contrast.

Echinacea and Rudbeckia: These plants all bloom around the same time, and the bright purples and yellows of Echinacea and Rudbeckia flowers contrast well with the blue or silver of Eryngium.

Sedum: Sedums have fleshy, succulent-like leaves and clusters of star-shaped flowers. Their rounded form makes a nice contrast to the spiky Eryngium, and they also share similar growing conditions.

Lavender: The silver-blue color of many Eryngium varieties complements the color of lavender flowers beautifully. They also both enjoy full sun and well-drained soil.

Roses: The spiky texture of Eryngium contrasts nicely with the soft petals of roses, and their blue or silver color can help to set off the color of the roses.

Salvia: With their spires of flowers, salvias can echo the form of Eryngium but provide a softer texture. Look for varieties with purple or blue flowers for a cool-colored theme, or contrast with red or pink varieties.

Drought-tolerant Perennials: If you’re gardening in a dry area, pair Eryngium with other drought-tolerant plants like Agastache, Perovskia (Russian Sage), or Penstemon.

Yarrow (Achillea): With its feathery foliage and flat-topped clusters of flowers, yarrow provides a strong contrast to the spiky form of Eryngium.

Coreopsis (Tickseed): These perennial plants produce masses of bright, cheerful, daisy-like flowers throughout the summer. They’re hardy, drought-tolerant, and they attract beneficial insects. Their flowers are typically yellow, but can also be found in pink and red varieties, providing a great color contrast to the blue-green of Eryngium.

Cosmos: Cosmos are annuals that bloom from summer to the first frost. They’re easy to grow, and they produce flowers in a range of colors, from white and pink to red, orange, and yellow. They grow tall and can provide a nice backdrop for the spiky Sea Holly flowers. Cosmos also attract a range of pollinators.

Zinnia: Zinnias are vibrant annuals that bloom heavily from summer to frost. They come in a multitude of colors and can add a pop to any garden. Like Cosmos, they grow fairly tall and attract butterflies, making them a wonderful companion for Eryngium.

Remember, the key to successful companion planting is to consider the needs of each plant and ensure they are compatible. Eryngium thrives in full sun and well-drained soil, so choose companions with similar needs.

Growing Tips

Growing Eryngium, also known as Sea Holly, isn’t too difficult if you provide the right conditions. Follow these steps:

Choose the right location: Eryngium thrives in full sun exposure – at least 6 hours of direct sunlight per day. The sunnier the site, the more intense the blue! It can tolerate partial shade, but it’s best to select a location where it can get a good amount of sunlight each day. The plant also prefers dry, poor to moderately fertile, well-drained soils except for Eryngium pandanifolium (Giant Sea Holly), which prefers moist soils. Sea Holly doesn’t do well in heavy clay or overly wet conditions.

Planting: Eryngium can be grown from seeds, divisions, or young plants. If you’re planting from seed, sow them in a cold frame in fall or spring. Divisions should be made in spring. For young plants, dig a hole twice the size of the root ball, place the plant in, and backfill with soil. Water thoroughly after planting. Eryngium is a tap-rooted plant that transplants poorly and is best left undisturbed once established. Select your site carefully!

Watering: Water the plants regularly during the growing season, but make sure you’re not overwatering. Eryngium does not like to sit in wet soil. Once established, it is quite drought tolerant.

Feeding: Sea Holly plants do not require fertilization. They may sprawl if grown in overly fertile soils.

Maintenance: Deadhead spent blooms to encourage more flowers. In fall, you can cut back the stems or leave them for winter interest and to provide food for birds.

Winter: Eryngium needs winter protection and a warm site to allow the e rosettes to overwinter successfully. Otherwise, these plants use up all their energy replacing foliage.

Pests and Diseases: Eryngium is fairly resistant to most pests and diseases. However, there are a few issues that gardeners should watch out for:

• Aphids: Like many garden plants, Eryngium can be affected by aphids. These small, soft-bodied insects feed on the sap of plants and can weaken them over time. They’re usually found on new growth or the undersides of leaves.
• Root Rot: This can occur if the plant is in poorly drained soil or watered excessively. Symptoms include yellowing leaves, stunted growth, and plant death. To prevent root rot, ensure your Eryngium is planted in well-draining soil and avoid overwatering.
• Powdery Mildew: Although it’s not very common, Eryngium can sometimes be affected by powdery mildew, especially in humid conditions or when there’s a lack of air circulation around the plant. This fungal disease manifests as a white, powdery coating on the leaves.