Red Dock 
Red flower prickly pear 
Red Glasswort 
Red Hot Chili Pepper Cactus 
Red sand spurrey 
Red Sorrel 
Redstem springbeauty 
Regal foxtail 
Reinwardt's Pitcher-Plant 
Rhodalsine geniculata 
Rock buckwheat 
Rock Soapwort 
Rose Campion 
Rosy Sundew 
Round-leaved Sundew 
Rumex aeroplaniformis 
Rumex cyprius 
Rumex nepalensis 
Rumex pictus 
Sabulina tenuifolia 
Sacred Column Cactus 
Saguaro cactus 
Salicornia virginica 
Salsola cyclophylla