Eryngium x tripartitum
I first saw this sea holly flowering splendidly in the purple borders at Sissinghurst Castle more years ago than I care to remember. It produces masses of flowers with metallic blue central cones and a spiky ruff. The overall effect is more discreet than the bold blue forms. As it’s a sterile hybrid the individual flowers last a particularly long time. The European varieties of sea holly have proved themselves to be very tough. Needs sun. 40cm x 50cm.