Weed Herbarium – by Scientific Name
| Sagina procumbens | birdseye pearlwort | Caryophyllaceae - Pink Family |
| Saponaria officinalis | bouncing bet | Caryophyllaceae - Pink Family |
| Schizachyrium scoparium | see - Andropogon scoparius |
| Scleranthus annuus | knawel | Caryophyllaceae - Pink Family |
| Scrophularia nodosa | common figwort | Scrophulariaceae - Figwort Family |
| Senecio jacobaea | tansy ragwort | Asteraceae (Compositae) - Aster or Sunflower Family |
| Senecio vulgaris | common groundsel | Asteraceae (Compositae) - Aster or Sunflower Family |
| Setaria lutescens | see - Setaria glauca | |
| Setaria faberi | giant foxtail | Poaceae (Graminae) - Grass Family |
| Setaria glauca | yellow foxtail | Poaceae (Graminae) - Grass Family |
| Sicyos angulatus | burcucumber | Cucurbitaceae - Gourd Family |
| Silene cucubalus | see - Silene vulgaris | |
| Silene alba | white cockle | Caryophyllaceae - Pink Family |
| Silene vulgaris | bladder campion | Caryophyllaceae - Pink Family |
| Silphium perfoliatum | cup plant | Asteraceae (Compositae) - Aster or Sunflower Family |
| Sinapis arvensis | see - Brassica kaber |
| Sisymbrium officinale | hedge mustard | Brassicaceae (Cruciferae) - Mustard Family |
| Smilax herbacea | carrion flower | Smilacaceae - Catbrier Family |
| Solanum carolinense | horsenettle | Solanaceae - Nightshade Family |
| Solanum dulcamara | bittersweet nightshade | Solanaceae - Nightshade Family |
| Solanum ptycanthum | eastern black nightshade | Solanaceae - Nightshade Family |
| Solidago canadensis | Canada goldenrod | Asteraceae (Compositae) - Aster or Sunflower Family |
| Solidago graminifolia | narrowleaf goldenrod | Asteraceae (Compositae) - Aster or Sunflower Family |
| Solidago sempervirens | seashore goldenrod | Asteraceae (Compositae) - Aster or Sunflower Family |
| Sonchus arvensis | perennial sowthistle | Asteraceae (Compositae) - Aster or Sunflower Family |
| Sonchus asper | spiny sowthistle | Asteraceae (Compositae) - Aster or Sunflower Family |
| Sonchus oleraceus | annual sowthistle | Asteraceae (Compositae) - Aster or Sunflower Family |
| Sorghastrum nutans | yellow Indiangrass | Poaceae (Graminae) - Grass Family |
| Sorghum halepense | Johnson grass | Poaceae (Graminae) - Grass Family |
| Spergularia rubra | red sandspurry | Caryophyllaceae - Pink Family |
| Stellaria graminifolia | see - Stellaria graminea | |
| Stellaria graminea | little starwort | Caryophyllaceae - Pink Family |
| Stellaria media | common chickweed | Caryophyllaceae - Pink Family |
| Symplocarpus foetidus | common skunk cabbage | Araceae - Arum Family |