Echinops ritro ssp. ruthenicus 'Platinum Blue' is a globe thistle with thistle-like leaves, silver stems and blue spheres of starry flowers.

Echinops ritro 'Veitch's Blue' is a great, somewhat old-fashioned perennial with wonderful shiny spheres that turn blue as the flowers open which ushers in a period of honey bee madness.

If you love cool plants and blue flowers, sea hollies will give you what you need.

Blue flower heads of the ultra-compact Eryngium planum 'Blue Hobbit' are surrounded by large frilled blue bracts.

Eryngium 'Jade Frost' has gorgeous variegated green and white foliage blushed with pink in spring and then topped with true blue thistle-like thimbles in summer.

Eryngium 'Neptune's Gold' is the first sea holly with totally gold leaves. It has classic blue thimbles and bracts that are blue and gold.

Eryngium 'Big Blue' is one of the best sea hollies with masses of blue, thistle-like thimbles.