Purple foxglove 
Purple Justicia 
Purple Mullein 
Purple Owl's-Clover 
Purple Porterweed 
Purple prairie verbena 
Purple Toadflax 
Purple witchweed 
Purple Wood Sage 
Purpletop Vervain 
Pursh's Wild Petunia 
Purslane speedwell 
Pycnostachys goetzenii 
Queen's wreath 
Rattail 
Red Bartsia 
Red Deadnettle 
Red Flame 
Red kittentails 
Red Turtlehead 
Red-stemmed Figwort 
Rhodope toothwort 
Ribwort Plantain 
Richweed