Showy Goldenrod 
Shrubby Dampiera 
Shrubby Everlasting 
Siam Weed 
Siebera nana 
Silver burr ragweed 
Silver Thistle 
Silver thistle 
Silver wormwood 
Silver-leaved yarrow 
silvercrown 
Silverpuffs 
Single-flower Knapweed 
Singlehead pussytoes 
Siphocampylus matthiaei 
Siphocampylus reticulatus 
Sky Blue Aster 
Slender Salsify 
Slender Sowthistle 
Slender woollyheads 
Slender-flower Thistle 
Slender-leaved elecampane 
Small tarweed 
Small white American-aster