Thorny blue

''Eryngium amethystinum'', amethyst sea holly, is a clump-forming, perennial, tap-rooted herb. Its stem is 30 to 50 cm long and is light blue to purple in colour. It has a basal circle of obovate, pinnate, spiny, leathery, mid-green leaves. It flowers in mid to late summer with cylindrical umbels, 2-3 cm long atop silvery blue bracts and branching stems. The plant is native to the eastern Mediterranean and prefers dry places and soils that are rich in calcium.