Eryngium planum – The blue-tinted cross thistle with a strong, architectural appearance

Eryngium planum, commonly known as blue sea holly or flat sea holly, is a striking herbaceous perennial instantly recognizable by its unique, almost sculptural shape. With its silvery-blue, branching stems and ovoid, spiky flower heads, it brings a modern, architectural touch to a variety of gardens. This hardy, sun-loving plant is not only visually striking but also a valuable nectar source for pollinators. Thanks to its drought tolerance and long flowering period, Eryngium planum is an excellent choice for gardeners looking to add a unique, low-maintenance plant to their borders.

Silver-blue stems and spiky flower heads

What makes Eryngium planum so special is the color and shape of its flowers. The plant forms straight, silvery-blue stems that branch elegantly, each crowned by compact, spiky, ovoid flower heads. These are surrounded by narrow, stiff bracts that give the plant a distinctly thistle-like appearance.

The flowers have a vibrant, deep blue to steel blue color, creating a strong contrast with traditional yellow, pink, or white flowering garden plants. This unique shade adds a cool, modern touch to the garden and creates a beautiful interplay with ornamental grasses or warm-colored flowers.

Long flowering period from mid-summer to early autumn

One of Eryngium planum's greatest assets is its long and reliable blooming period. From mid-summer until well into autumn, the flower heads remain on the stems, adding color and texture for much of the season.

Even when the flowers begin to dry, they retain their texture and decorative value, meaning they will remain beautiful in the garden for months to come.

Drought tolerant and ideal for sunny locations

The blue erect thistle is a plant that prefers full sun and well-drained, dry to moderately moist soil. Once established, it is remarkably drought-tolerant, making it particularly suitable for:

• Sunny borders

• Cottage and prairie gardens

• Gravel gardens and rock gardens

• Mediterranean vegetation

• Nature-friendly and low-maintenance gardens

Its silver-blue color is ideal for landscapes with plenty of light and warmth, and it thrives in places where many other perennials struggle with drought.

A magnet for bees, butterflies and other pollinators

Eryngium planum is a valuable nectar plant and is known for its attraction to all kinds of pollinators:

• Bees

• Bumblebees

• Butterflies

• Gliding

Its rich nectar production makes it particularly suitable for gardens focused on biodiversity and natural value. It's a real asset to ecological gardening.

Excellent as a cut and dried flower

Besides its ornamental value in the garden, the blue erect thistle is very popular with florists. The sturdy flower heads and stems make the plant ideal as a cut flower, and they last a particularly long time in a vase.
When dried, the flowers retain much of their structure and a subtle blue hue, making them perfect for:

• Dried bouquets

• Flower arrangements

• Craft decorations

• Natural interior projects

Easy to maintain and strong

Eryngium planum requires little attention. Remove old, dried-out stems in early spring to make room for new growth. Furthermore, the plant requires little fertilizer or additional care. Its robust root system makes it very hardy and reliable.

Why choose Eryngium planum?

• Unique silver-blue, thistle-like bloom

• Long flowering period from summer to autumn

• Very drought tolerant and low maintenance

• Fantastic bee and butterfly plant

• Excellent cut and dried flower

• Suitable for sunny borders, rock gardens and cottage gardens

• Adds architectural structure and color to the garden