I started some Linum perenne this spring. It’s a perennial, and I didn’t expect much from it this year. However, the seedlings grew strongly and have been blooming spasmodically all summer. The individual flowers are small, but during the main flush of bloom in early summer established plants are solid blue mounds. (I had a fine specimen years ago that in flower was a blue hemisphere with a radius of about fifteen inches. Then the family cat decided that it was a nice spot to nap.)
Nolana paradoxa, or Chilean bellflower, is one of this year’s experiments. It may look like a morning glory, but it’s actually in the nightshade family, like petunias and potatoes. The plant creeps along the ground and would probably make a good ground cover. It blooms steadily but not profusely, but anything blue is welcome in the summer. Online sources stress that it likes heat and dryness, but I think they overstate the case. The plants definitely look unhappy in triple-digit temperatures without a little extra water.
This celosia suggests an early iteration of a space-filling curve.
try California Blue Bells, I experimented this year with them and they’re pretty profuse bloomers, the hummers love them. long time to germinate.
I grow Phacelia campanularia most years, probably the most intensely blue flower you can grow in Kansas. They bloom spectacularly for a month. Then the weather gets hot and they fade out.