Eryngium is the largest genus in the carrot family, with about 250 species distributed across the world. The largest diversity of species is in South America but, of the 25 found in Europe, the sea holly (Eryngium maritimum) and the scarce field eryngo (Eryngium campestre) are British native species.
The intense metallic blue of the inflorescences of Eryngium planum 'Blaukappe' (in the Merton Borders in the Botanic Garden) is common to many Eryngium species and, combined with their striking architecture, makes them popular garden plants. Resentful of root disturbance, eryngiums establish well when sown directly. Species such as Eryngium maritimum are adapted to the inhospitable environment of coastal habitats with extensive root systems and thick, waxy foliage. The blue colouration of the inflorescence, caused by anthocyanin, may well protect the plant from strong sunlight; extreme conditions, such as high light levels, and poor soils, intensify this colour.
Common names such as sea holly and the Watling Street Thistle (Eryngium campestre) suggest that the genus is not typical of the Apiaceae. The dense, stalkless umbel is surrounded by long, spiny bracts and does have a superficial resemblance to a thistle. The leaves of many species, such as Eryngium yuccifolium, have are strap-like leaves with parallel venation, as is typical of monocots.
Eryngium has been used as food and medicine across the world. Eryngium foetidum is a popular culinary herb in India, imparting a taste somewhat like coriander. Eryngium planum has been used as a traditional remedy for whooping cough in Transylvania and some American species were believed to be effective against snake bites. Modern medical research has identified potential uses in the treatment of skin conditions. Roots of Eryngium maritimum were collected widely in seventeenth-century England to be candied as 'Eryngoes'. These lozenges were credited with tonic and aphrodisiac properties. In The Merry Wives of Windsor, Falstaff calls for the sky to 'hail kissing-comfits and snow eringoes [/] let there come a tempest of provocation'. Whilst Elizabethan Colchester became known for its production of 'Oysters and Eringo Root'.
The Eryngium giganteum cultivar, 'Miss Willmott's Ghost', was so-called after the eccentric Ellen Willmott probably not, as Christopher Lloyd suggested, 'because she was pale and prickly', but after her habit of sowing the seed wherever she visited. This fascinating and varied genus has retained its popularity as an ornamental perennial and its allure as a scarce wild plant of British seashores and fields.
Brickell C 2008. RHS A-Z encyclopedia of garden plants. Dorling Kindersley.