Sea holly (Eryngium planum 'Jade Frost')
Eryngium planum 'Jade Frost' sea holly offers striking variegated foliage and violet-blue summer blooms. Ideal for dry, sunny gardens.
Complete Plant Information
Overview
Eryngium planum ‘Jade Frost’ is a standout herbaceous perennial, highly valued for its complex texture and striking coloration. This cultivar of sea holly boasts blue-green leaves intricately edged in creamy white variegation, which can even emerge with a rosy pink blush in cool weather. Its upright, architectural habit provides excellent vertical interest throughout the summer months.
The appeal of Eryngium planum ‘Jade Frost’ extends beyond its foliage; it produces thistle-like, violet-blue flower heads subtended by spiky bracts, making it an excellent specimen for modern and drought-tolerant landscapes. As a low-maintenance, low-water plant, the sea holly thrives where many other perennials struggle.
Gardeners appreciate the long-lasting interest provided by this plant, from its patterned basal rosettes to its long season of unique bloom. Once established, this tough perennial offers reliable, specialized color, making the Eryngium planum ‘Jade Frost’ a fixture in sunny, well-drained borders.
Fast Facts
- Plant Family: Apiaceae
- Plant Type: Herbaceous perennial
- Hardiness Zones: USDA Zones 5-8
- Size at Maturity:
- Height: 1.5-2.5 ft
- Spread: 1-1.5 ft
- Bloom Time: June to August
- Bloom Description: Violet blue
- Sun Exposure: Full sun
- Water Needs: Dry
- Maintenance Level: Low
How to Grow
Planting sea holly is best achieved in spring after the last frost, or early fall, ensuring it has time to establish its critical taproot. Select a location receiving full sun, as insufficient light can cause taller stems to sprawl unattractively. This species requires sandy, well-drained soil; it readily tolerates poor soils but absolutely demands dryness to prevent root issues.
Watering should be minimal once established, as Eryngium planum ‘Jade Frost’ is highly drought tolerant. Avoid the temptation to overwater, which is the quickest way to harm this plant. Fertilization is generally unnecessary; overly fertile soils can contribute to floppiness.
Pruning is minimal. Deadhead spent flower heads if desired, although they are attractive when dried. Crucially, because this is a taprooted plant, it transplants poorly. Establish your Eryngium planum ‘Jade Frost’ in its final spot, as it prefers to be left undisturbed.
Landscape Uses
The unique texture and coloration of Eryngium planum ‘Jade Frost’ make it a superb choice for contemporary or xeriscape plantings. Its upright stance adds necessary structure to beds and borders, contrasting beautifully with soft, mounding perennials. It is an excellent selection for sun-baked areas of the landscape where intense heat discourages less resilient species.
Use sea holly effectively as a single specimen to highlight its variegated foliage, or group several plants together for greater impact against a neutral backdrop, such as gravel mulch or pale stone walls. The stiff, architecturally interesting stems and heads lend themselves well to modern drifts and textural gardens.
Beyond the garden, the flower heads of Eryngium planum ‘Jade Frost’ are celebrated for floral design. They transition seamlessly from fresh bouquets to dried arrangements, offering prolonged ornamental value long after summer color fades.
Standout Features
Flower Qualities
- Showy
- Good Cut
- Good Dried
Noteworthy Characteristics
Eryngium planum, commonly called sea holly, is a coarse, clump-forming perennial featuring a summer bloom of steel-blue, thistle-like flower heads on branched stems rising from a rosette of dark green basal leaves. ‘Jade Frost’ is a variegated cultivar that features showy blue-green leaves with bold creamy white margins and violet-blue flowers and flowering stem branches. In cool temperatures, the margins of new leaves emerge a showy pink before eventually turning creamy white.
Tolerances
- Drought
- Dry Soil
Potential Problems
Eryngium planum ‘Jade Frost’ is generally robust, facing few serious insect or disease challenges under proper conditions. The primary threat involves moisture; if planted in heavy or consistently damp soils, the plant is highly susceptible to root rot. Ensure excellent drainage is provided.
Occasionally, common garden pests like aphids, slugs, or snails may appear, though they rarely cause significant damage to the mature, spiny foliage. Watch for potential leaf spot diseases, especially if humidity is high or air circulation is poor near the basal leaves. Management focuses on cultural control: positioning the plant correctly in full sun and maintaining dry soil conditions.
Frequently Asked Questions
What hardiness zones is Sea holly suitable for?
Eryngium planum ‘Jade Frost’ is hardy in USDA Zones 5 through 8, making it quite versatile across many temperate climates.
How large does Sea holly grow?
This herbaceous perennial typically reaches a modest height between 1.5 and 2.5 feet, with a spread ranging from 1 to 1.5 feet wide.
What sun exposure does Eryngium planum ‘Jade Frost’ need?
For the best density and to prevent sprawling, this plant requires full sun exposure throughout the day.
When does Sea holly bloom?
The violet-blue, thistle-like flowers appear reliably during the summer months, specifically from June through August.
Conclusion
For gardeners seeking structure, architectural form, and exceptional drought tolerance, Eryngium planum ‘Jade Frost’, or sea holly, is an outstanding selection. Its variegated foliage ensures season-long visual interest, complementing the unique summer bloom. Before planting, confirm that your site offers full sun and excellent drainage to ensure many seasons of low-maintenance enjoyment from your sea holly.
Companion Planting
Because the cultural needs of Eryngium planum ‘Jade Frost’ center around intense sun and dry, poor soils, successful companion planting relies on selecting other grit-tolerant species. Pair it with plants that hate wet feet, such as ornamental grasses like Stipa tenuissima (Mexican feather grass) or drought-tolerant Mediterranean herbs like Lavender (Lavandula) or Thyme (Thymus). These combinations create a tapestry of fine texture contrasted against the bold, spiky structure of the sea holly.
Avoid placing Eryngium planum ‘Jade Frost’ beside moisture-loving perennials like Hostas or Astilbes; the extra water they require will quickly compromise the sea holly’s health and risk root rot. Focus on companions that thrive in similar harsh, sunny conditions to maintain a cohesive planting scheme.
Design Ideas for Variegated Texture
The creamy white margins on the foliage of Eryngium planum ‘Jade Frost’ serve as an excellent textural highlight in the garden, acting almost like a soft, living mulch when viewed from above. Use this plant near the edge of a border, allowing the basal rosettes to soften hardscape edges, or mass plant them to create a shimmering, pale-green carpet punctuated by spiky blue flowers.
The coloration is particularly effective when contrasted against deep purple or dark red plantings. Consider placing it near dark-leaved Sedums or deep purple Russian Sage (Perovskia atriplicifolia). The violet-blue blooms of the sea holly harmonize beautifully with silvery foliage plants, emphasizing a cool-toned, moonlit garden palette.
