The genus Eryngium, popularly known as blue thistle or sea thistle, stands out in the family apiaceae for its spectacular inflorescences, its resistance and the variety of species distributed throughout the world.
These thorny plants, far from being simple thistles, They offer great ornamental and functional value in gardens and outdoor spaces. Furthermore, their distinctive metallic blue or white appearance, combined with their ability to thrive in infertile areas, makes them a popular choice for both sustainable gardening and modern landscaping.
What is Eryngium? Origin and general characteristics
eryngium It is a genus of herbaceous plants that mainly includes perennial and biennial species, although there are also some annual ones. There are about 250 species accepted and its distribution is cosmopolitan: America (with special presence in South and Central America), Europe, North Africa and Asia are regions where different varieties abound.
They are generally glabrous plants, with erect and highly branched stems, and leaves of variable shapes: from linear to orbicular, often deeply lobed and provided with sharp spines, a key characteristic that gives them their protective function in gardens.
Inflorescences and flowers: Eryngium is distinguished by its compact inflorescences, usually in spherical, racemose, or panicle heads, surrounded by spiny, blue, white, or purple bracts. The metallic, bright colors, especially the blues, are due to pigments called anthocyanins, which also help protect the flowers from the intense sun.
After pollination—carried out by pollinating insects such as bees and butterflies—they develop small globose or obovoyoid fruits, which are usually covered with scales or tubercles. Dispersal is primarily anemochorous (by wind), allowing them to colonize open areas or coastal dunes.
Among its highlights:
- Life habits: Annuals, biennials or perennials.
- Level: From dwarf species that barely reach 2-10 cm (Eryngium viviparum) up to varieties that reach almost 2 meters (Eryngium yuccifolium).
- Sheets: Linear to lobed, with spines on the margins and a leathery surface in many species.
- Flowers: Dense flower heads with sessile floral units, white, blue, violet or silver in colour.
Therefore, Eryngium is one of the most valued plants for its resistance, beauty and usefulness in low-intervention spaces. or sustainable gardening.
Main species of Eryngium
- Eryngium alpinum.
Thorny perennial native to the Alps and Balkans in Europe. It can reach a length of about 60 cm., with elongated, spiny leaves. Its silvery-blue flower heads are notable. Widely cultivated in gardening for its hardiness and summer flowering. Featured variety: 'Superbum' (extra-large, deep blue flowers, approximately 75 cm tall).
- Eryngium bourgatii.
Native to the Iberian Peninsula, especially the Pyrenees and the Central System. Popularly known as panicle or white thistle. It reaches 45 cm and blooms in spring and summer with bluish heads and indented leaves. It is highly valued for its elegance in rock gardens and xeriscapes.
- eryngium campestre.
A perennial native to Europe, North Africa, and the Middle East; it is known as the running thistle, tinder thistle, or mushroom thistle. It can grow up to 70 cm tall, is heavily prickled, and has bluish flower heads about 3 cm in diameter. This plant is particularly drought-resistant and very useful in Mediterranean gardens and sandy areas.
- Eryngium foetidum.
Known by many popular names, such as coyote cilantro, recao, sacha culantro, habanero cilantro, or chillangua, depending on the region, it is native to tropical America and widely cultivated throughout Latin America and Southeast Asia as a culinary and medicinal herb. It has edible lanceolate leaves (up to 30 x 5 cm), yellowish-green flowers, and can vary between 5 and 60 cm in height depending on the conditions.
Important in Caribbean and Amazonian cuisine, and in numerous traditional recipes. Its leaves are used fresh or dried to flavor stews, soups, and rice dishes. In folk medicine, it is attributed with digestive, stimulant, and anti-inflammatory properties. It is a profusely branched plant and is either annual or perennial depending on the climate. - Eryngium yuccifolium.
A perennial native to North America (prairies and grasslands), also called rattlesnake master, it grows to a height of 1,80 meters, has long, narrow leaves, and flowers grouped in greenish or whitish umbels, about 3 cm in diameter. Its roots were used by Native Americans to treat snakebites and have various ethnobotanical applications.
- Clump coast.
Known as sea thistle, it is a perennial species characteristic of dunes and coastal sandbanks throughout the Mediterranean and Atlantic regions of Europe. A robust plant, 15 to 60 cm tall, with a branched stem and leathery basal leaves, wider than they are long, blue-green to silvery in color, with spiny lobes. Its flower heads are bluish to silvery, up to 3 cm long.
This plant is highly tolerant to salinity and wind, which is why it is used in dune restoration and coastal soil protection. Both young shoots and roots can be eaten cooked or blanched, and in traditional medicine, it is used as a diuretic, detoxifier, expectorant, and aphrodisiac. - eryngium planum.
A perennial native to Europe and western Asia, it grows to about 60 cm tall and has bluish flower heads and basal leaves. It is prized for both its ornamental and medicinal value (as a diuretic and appetite stimulant), and is ideal for cut flowers, both fresh and dried. It is a favorite species in modern gardens and floral arrangements due to its intense color and ability to attract pollinators.
- Eryngium viviparum.
A very small (2–10 cm tall), thornless perennial species found in northwestern Spain and France. It produces blue flowers, is adapted to acidic soils, and is found in humid areas and peat bogs. Very rare and with a localized distribution, it is protected in several regions due to its scarcity.
- Other notable species:
- Eryngium giganteum: A variety with an imposing appearance, up to 120 cm, with silvery-blue inflorescences.
- Eryngium variifolium: Native to Morocco, used ornamentally in dry gardens.
- Organic Blue Eryngium: Cultivar appreciated in organic floriculture for its bright blue flower heads, resistant to cold and very attractive to bees and pollinators.
The genus Eryngium is extensive, with numerous native and exotic species, each adapted to particular ecological conditions ranging from sandy coasts to alpine meadows or mountains.
Habitat and Ecology of Eryngium
Eryngium occupies an extraordinarily wide range of habitats, from saline coastal soils, dunes, sandbanks, roadsides, and dry grasslands to mountainous lands and wetlands. They are capable of growing in poor, dry, sandy, and even alkaline soils, withstanding sun exposure and drought well.
In Mediterranean regions, many species are found in primary and secondary dunes (Eryngium maritimum), playing a relevant ecological role as soil fixers and in the protection of coastal biodiversity.
- Tolerance: Highly tolerant of salinity, drought, and wind. They generally prefer sunny environments and well-drained soils.
- Environmental indicators: Some species, such as E. maritimum, are indicators of soils with basic pH (5.5-8), rich in bases, and of habitats disturbed only occasionally by mowing or grazing.
- Dispersion: Mainly by wind, although they can also be dispersed by the dragging of entire plants in arid environments (tumbleweeds).
- Biological type: In Raunkiaer's classification, the majority are hemicryptophytes: They develop replacement buds at ground level and are resistant to cold.
Ornamental properties and landscape value
Eryngium is highly valued in contemporary and sustainable gardening because:
- Its strong sculptural and colorful presence in both xerophilous gardens and urban green areas.
- Its ability to grow in marginal and poor soils, where most conventional species fail.
- The long lifespan of its flowers, which are highly appreciated as cut flowers (fresh and dried) for bouquets, floral arrangements and long-lasting decorations.
- Protecting garden areas: They act as a natural barrier due to their thorns and rigid shape, limiting the passage of animals and delimiting spaces.
- His role in the pollinator conservation, since the inflorescences attract bees, butterflies and other insects necessary for ecological balance.
Culinary, medicinal and traditional uses of Eryngium
Eryngium offers much more than beauty:
- Gastronomy:
species like Eryngium foetidum They are widely used as aromatic herbs, especially in American and Asian tropical cuisine as a substitute for cilantro (see difference with parsley). Its leaves flavor rice dishes, soups, sauces (such as Panamanian "recao verde" or Caribbean sancocho), stews, and salads. In Europe, the tender shoots and roots of Clump coast They are consumed blanched or cooked as a substitute for asparagus.
The aroma and flavor are more intense and long-lasting than common cilantro, and in many regional cuisines it is considered essential. - Traditional medicine:
Eryngium yuccifolium y Clump coast They have a long history of use as a diuretic, detoxifier, laxative, aphrodisiac, expectorant, and anti-inflammatory. In American and African cultures, they are prescribed for digestive problems, respiratory illnesses, gynecological conditions, and as a remedy for snake bites or to stimulate the appetite.
They contain essential oils, saponins, flavonoids, coumarins and phenolic compounds responsible for these effects.
Some species, especially Clump coast, were traditionally used as aphrodisiacs and tonics, and the consumption of infusions of roots and leaves is documented in European phytotherapy. - Other traditional uses:
In some countries, Eryngium roots are eaten as a vegetable, the tender shoots are used in salads, and its dried leaves decorate floral arrangements and crafts.
Blue thistle is also useful for ecological restoration, sustainable gardening, and restoring degraded habitats.
It is important to note that medicinal use should always be done under professional supervision, given the potential of some active compounds.
Growing and caring for Eryngium in the garden and in pots
Essential requirements for optimal growth
- Sunlight: They prefer locations with direct sunlight for most of the day. Intense sun exposure not only promotes growth but also intensifies the blue color of the flower heads thanks to anthocyanins.
- Substratum: Dry, sandy, well-drained soils. It tolerates poor soils and arid areas where other plants do not thrive. Excessive moisture and waterlogging cause root rot.
- Irrigation: Scarce. It tolerates drought well and only requires light, spaced watering during the warmer months. Excess water promotes the development of disease.
- Fertilizer: Poor, as excess nutrients reduce the intensity of the color and weaken the structure. Organic compost or liquid fertilizer can be applied to the pot, but always in moderation.
- Climate: Cold-resistant, suitable for coastal areas and humid climates, although it prefers dry and temperate environments.
How to plant Eryngium correctly
- Planting time: Sowing is recommended in spring or, in the case of species that require vernalization, in autumn to withstand the cold and improve germination.
- Place seeds in seedling trays or pots with specific substrate, separated and shallow.
- Water gently and expose to direct sunlight. They germinate in 8-15 days, although some species may take longer if the seeds are not fresh.
Transplant and maintenance
- Transplant: Plant when the seedling has visible roots in the drainage system. Plant in a sunny area of the garden or in a larger pot with lean, well-drained soil. Do not over-handle the roots, as they are sensitive.
- Pruning and cleaning: Remove diseased, old leaves and eliminate mature flower spikes to prolong the life of the plant (especially in the case of Eryngium foetidum).
- Subscriber: For potted plants, use liquid fertilizer every two weeks during the growing season; for soil, use compost or well-cured manure occasionally.
- Plagues and diseases: Resistant, although it can be attacked by aphids, slugs and snails. The most feared disease is root rot due to overwatering. Control is based on avoiding waterlogging and manually removing parasites when they appear.
- Associations: Perfect in combination with ornamental grasses, lavenders, salvias and rockery plants to create colorful dry landscapes.
- Multiplication: In addition to seed, some species allow separation of offspring and cuttings, although most respond better to sexual reproduction.
- Practical tips: Don't repot frequently, as Eryngium prefers to establish and expand without intervention. Soils too rich in organic matter or fertilizers can diminish color and vigor.
Eryngium in floriculture and floral design
Its use stands out in:
- Cut flower: For bouquets, arrangements, centerpieces, and dried arrangements. Ideal for weddings, events, and long-lasting decor.
- Dried flower: It is harvested when the flowers are at their peak and dried in bright, well-ventilated areas. Its color and texture are maintained for months.
- Modern arrangements: The contrast between the metallic blue of Eryngium and the warm tones of grasses or white flowers creates avant-garde and sophisticated combinations.
- Ecological restoration: In dunes and degraded soils, urban reforestation and as an element of biodiversity.
Curiosities, etymology and historical data
The name Eryngium It comes from the Latin ēryngē, -ium, taken in turn from the Greek ἡρύγγιον, used since ancient times for various species of thistles with medicinal properties, mentioned by Theophrastus, Dioscorides and Pliny the Elder.
The type species of the genus is Clump coast, described by Linnaeus, which has historically symbolized coastal resilience and protection in European folklore. Furthermore, each country and region has its own vernacular names, depending on culinary and medicinal uses (e.g., "recao" in Puerto Rico, "chillangua" in Colombia and Ecuador, "culantro coyote" in Costa Rica, "cardo marino" in Spain).
Frequently asked questions and doubts about Eryngium
- Is Eryngium toxic?
In general, it is not considered toxic to people or pets. Some species may contain compounds that cause discomfort if ingested excessively, although in most cases the leaves and shoots are consumed as vegetables or as a condiment. - Can it be grown indoors?
This genus is ideal for outdoor cultivation due to its need for direct sunlight and dry soil. Indoors, it only thrives in very bright light and adequate ventilation. - Is it suitable for low-maintenance gardens?
Without a doubt, it is one of the best plants for low-water, low-maintenance, and sustainable gardens, especially in arid or coastal areas.
The Eryngium genus stands out as an example of a resilient, aesthetic, and multifunctional plant. Whether used to protect gardens, enjoy long-lasting blooms, in cooking or traditional medicine, or as a decorative element in contemporary landscaping, blue thistles demonstrate why they have fascinated horticulturists, botanists, and garden lovers for centuries. Their easy cultivation and great adaptability make them a safe investment for both experts and amateurs.