Buy Flowers › Eryngium planum 'Blaukappe' - 4" Pot Eryngium planum 'Blaukappe' - 4" Pot $6.50 Sea holly, 3' tall stems with blue silvery gray flowers, and gray stems, upright, re-seeds, great sturctural plant, perennial zone 4-8, sun Add To Cart Added! Sea holly, 3' tall stems with blue silvery gray flowers, and gray stems, upright, re-seeds, great sturctural plant, perennial zone 4-8, sun