| Common name (English) | |
|---|---|
| Casuarina glauca | Swamp oak |
| Catalpa bignonioides | Catawba, American catalpa |
| Catharanthus roseus | Madagascar periwinkle, Billygoat Weed |
| Cedrus atlantica | Atlantic cedar, Atlas Cedar |
| Cedrus deodara | Deodar |
| Cedrus libani | Cedar of Lebanon |
| Ceiba pentandra | Kapok |
| Ceiba speciosa | Floss-silktree, Silk Floss Tree |
| Celtis australis | European nettle tree, European Hackberry |
| Cenchrus clandestinus | Kikuyo Grass |
| Cenchrus purpureus | Napier grass, Elephant grass |
| Cenchrus setaceus | African Fountain Grass |
| Cercis siliquastrum | Judas tree, Red Bud |
| Cestrum nocturnum | Night Jessamine, Queen of the Night, Night-blooming Cestrum |
| Chasmanthe aethiopica | |
| Chilopsis linearis | Desert willow |
| Clematis vitalba | Old man's beard |
| Cordyline cannifolia | Canna-leaved Palm-lily |
| Corylus avellana | Common hazel, Barcelona-nuts |
| Cosmos bipinnatus | Cosmos; Mexican aster |