Blue flowered eryngo (Eryngium aquaticum) is a perennial with pale whitish-blue to lavender to cornflower blue flowers. It may reach 1-4 feet tall by 3-4 feet wide so it's best to space plants at least 12 inches to 3 feet apart. It requires full sun to moderate shade in moist to wet, acidic soil. It is a great nectar source for pollinators.
/mp