1. North American annual with small white flowers widely naturalized as a weed in South America and Europe
   - purslane speedwell

Type of: speedwell, veronica

• genus Cladrastis
• genus Clangula
• genus Clathrus
• genus Claviceps
• genus Claytonia
• genus Cleistes
• genus Clematis
• genus Cleome
• genus Clethra
• genus Clethrionomys
• genus Clianthus
• genus Cliftonia
• genus Clinopodium
• genus Clintonia
• genus Clitocybe
• genus Clitoria
• genus Clostridium
• genus Clupea
• genus Clusia
• genus Cnemidophorus
• genus Cnicus
• genus Cnidoscolus
• genus Coccothraustes
• genus Cocculus
• genus Coccus