Southwestern mock vervain 
Spanish Peaks Foxglove 
Spathodea 
Spearmint 
Spiked speedwell 
Spiny Bear's-Breech 
Spotted Beebalm 
Spotted Deadnettle 
Spotted emu bush 
Stachys aegyptiaca 
Stachys arabica 
Stachys arenaria 
Stachys cretica 
Stachys libanotica 
Stachys longispicata 
Stachys neurocalycina 
Stachys palustris 
Stachys paneiana 
Stachys spinulosa 
Stachys woronowii 
Stachys zoharyana 
Starry Leucas 
Staurogyne spathulata 
Stinging Hemigraphis