Attractive heads provide form and interest in the border. Eryngium planum (Sea Holly) via garden.ee: This herbaceous perennial thistle has branched silvery-blue stems and and numerous small blue conical flowerheads surrounded by spiky bracts.
Backlit Bull Thistle by Jim Crotty
Thistle Digi Digital Stamp by crookedlittlestudio on Etsy
Thistle Sea Holly by Lime Tree Studio