Callirhoe

Campanula

Campion

Candle Larkspur

Candytuft

Cardinal Flower 

Carpathian Bellflower

Catchfly

Catmint 

Centaurea

Cheddar Pinks

Chelone

Chinese Globeflower 

Clematis

Clustered Bellflower

Columbine 

Coneflower
Conoclinium

Coral Bells 

Coreopsis

Cranesbill 

Creeping Phlox 

Creeping Speedwell

Creeping Stonecrop

Creeping Thyme

Crested Iris

Crocosmia

Culver's Root

Blue: © Wit’s End Gardens
Ernest Markham: Szczepan Marczynski via Walters Gardens
Robin: © Wit’s End Gardens
regia: © Wit’s End Gardens