Eryngium yuccifolium

Eryngium yuccifolium is characterised by a rosette of long evergreen leaves resembling the vegetation of a yucca, hence its other name of yucca-leaved eryngo. This tall thistle blooms in summer, with small ovoid flower heads ranging in colour from whitish-grey to bluish-green. With its unusual yet delicate appearance, this perennial sea holly brings volume and charm to sunny flower beds. It thrives in ordinary, well-drained soil, and from moist to dry conditions. It tolerates poor soil.

Eryngium yuccifolium belongs to the Apiaceae family, just like carrots and parsley. It is native to the great plains of the central and eastern United States, being found from Minnesota to Ohio, and further south to Texas and Florida. It is also reported to be present in Connecticut, New Jersey, Maryland, and Delaware.

This herbaceous perennial plant forms a rosette of leaves reaching about 90cm (35in) in height and 60cm (24in) in width. The leaves are evergreen, rigid, linear, elongated, and narrow, ending in a sharp point. Each leaf measures 15 to 90cm (6 to 35in) long and 1 to 3cm (1in) wide, with a margin adorned with hairs and spines. Their bluish-green colour is due to a wax layer. Flowering occurs from July to September, depending on the climate, and lasts nearly two months. Branching stems emerge from the rosette at a height of 1.5m (5ft), well above the foliage. Each stem bears 10 to 40 inflorescences. Each inflorescence is an ovoid head, measuring 1 to 3cm (1in) in diameter and 2 to 4cm (1 to 2in) in length, composed of numerous tiny whitish flowers. Each flower is surrounded by small green and spiny bracts. This flowering attracts many pollinating insects. The seeds of this thistle can self-sow in light soil. The root system of this plant does not appreciate disturbance: it consists of a taproot surrounded by thick and fleshy fibrous roots.

This yucca-like thistle blends well into a contemporary, rustic, or wild setting. This curious plant works wonders in a large rockery with well-drained soil, especially in winter. Its airy and luminous flowering lightens up any other plants in a large sunny flower bed. It looks stunning alongside crocosmia, blue and black spike agastaches (Agastache 'Black Adder'), red oriental poppies, black dahlias, or pink coneflowers. It also pairs well with giant grasses (Panicum virgatum, Miscanthus sinensis), rockroses, lavenders, rosemary, or tall mulleins in drier gardens. Create country-style bouquets with its fresh or dried flowers.