Eryngium is a genus of flowering plants in the family Apiaceae. There are about 250 species. The genus has a cosmopolitan distribution, with the centre of diversity in South America. Common names include eryngo and amethyst sea holly (though the genus is not related to the true hollies, Ilex).
These are annual and perennial herbs with hairless and usually spiny leaves. The dome-shaped umbels of steely blue or white flowers have whorls of spiny basal bracts. Some species are native to rocky and coastal areas, but the majority are grassland plants. In the language of flowers, they represent "admiration".
Illustrated here is Eryngium x zabelii ‘Big Blue’, a common garden and cut flower. It produces especially large heads of steel-blue prickly flowers over a mound of silvery leaves that add texture to the sunny border. Exceptionally good for cutting, fresh or dried. Plants are mid-sized in habit with strong stems. A versatile plant, fitting well into the border and also useful in containers. Drought tolerant once established. Sea Holly is an easy-care perennial that adapts well to most sunny areas with average to dry soil. Remove old stems to ground level in late Autumn or early Spring.