Stylidium beaugleholei 
Stylidium laricifolium 
Stylidium productum 
Sulfur Cosmos 
Swamp isotome 
Swamp Marigold 
Swamp Sunflower 
Swamp thistle 
Sweet Everlasting 
Sweet Joe-Pye weed 
Symphyotrichum subulatum 
Syrian Cornflower-thistle 
Syrian Wild Artichoke 
Tagetes tenuifolia 
Tahoka Daisy 
Takhtajaniantha 
Tall beggarticks 
Tall blue lettuce 
Tall Elephant's-Foot 
Tall Lettuce 
Tall lobelia 
Tall Rattlesnakeroot 
Tall thistle 
Tanacetum aucheri