Burflower-Tree 
Burser's Gentian 
Butterfly Weed 
Buttonbush 
California Centaury 
Callipeltis aperta 
Callipeltis cucullaris 
Callipeltis factorovskyi 
Calotrope 
Candy Corn Vine 
Canscora diffusa 
Canscora perfoliata 
Caralluma sinaica 
Caralluma tuberculata 
Caribbean Milkweed 
Carissa carandas 
Catchweed Bedstraw 
Catharanthus coriaceus 
Catharanthus longifolius 
Catharanthus ovalis 
Caucasian Crosswort 
Centaurium maritimum 
Centaurium portense 
Ceropegia attenuata