Index of plants by genus
| Species | Common Name | Family |
| Sabatia difformis | Lance-leaved Rose Gentian | Gentianaceae |
| Sagittaria engelmanniana | Engelmann's Arrowhead | Alismataceae |
| Sagittaria graminea | Grass-leaved Arrowhead | Alismataceae |
| Sagittaria latifolia | Arrowhead | Alismataceae |
| Salix bebbiana | Bebb's Willow | Salicaceae |
| Salix candida | Sage-leaved Willow | Salicaceae |
| Salix cordata | Sand Dune Willow | Salicaceae |
| Salix discolor | Pussy Willow | Salicaceae |
| Salix eriocephala | Heart-leaved Willow | Salicaceae |
| Salix humilis | Prairie Willow | Salicaceae |
| Salix interior | Sandbar Willow | Salicaceae |
| Salix myricoides (glaucophylloides) | Blue-leaved Willow | Salicaceae |
| Salix planifolia | Tea-leaved Willow | Salicaceae |
| Salix pyrifolia | Pear-leaved Willow | Salicaceae |
| Salix sericea | Silky Willow | Salicaceae |
| Salix serissima | Autumn Willow | Salicaceae |
| Salix uva-ursi | Bearberry Willow | Salicaceae |
| Sambucus canadensis | Elderberry | Caprifoliaceae |
| Sambucus racemosa | Red Elderberry | Caprifoliaceae |
| Sanguinaria canadensis | Bloodroot | Papaveraceae |
| Sanguisorba canadensis | American Burnet | Rosaceae |
| Sanicula canadensis | Canada Sanicle | Apiaceae |
| Sanicula marilandica | Maryland Sanicle | Apiaceae |
| Sanicula odorata | Clustered Black Snakeroot | Apiaceae |
| Sanicula trifoliata | Large-fruited Sanicle | Apiaceae |
| Sarracenia purpurea | Pitcher Plant | Sarraceniaceae |
| Sassafras albidum | Sassafras | Lauraceae |
| Satureja vulgaris | Wild Basil | Lamiacaea |
| Saururus cernuus | Lizard's Tail | Saururaceae |
| Saxifraga pensylvanica | Swamp Saxifrage | Saxifragaceae |
| Saxifraga virginiensis | Early Saxifrage | Saxifragaceae |
| Scheuchzeria palustris | Pod-grass | Scheuchzeriaceae |
| Schizaea pusilla | Curlygrass Fern | Schizaeaceae |
| Scirpus atrovirens | Green Bulrush | Cyperaceae |
| Scirpus cyperinus | Woolgrass | Cyperaceae |
| Scirpus expansus | Woodland Bulrush | Cyperaceae |
| Scirpus fluviatilis | River Bulrush | Cyperaceae |
| Scirpus hattorianus | Mosquito Bulrush | Cyperaceae |
| Scirpus microcarpus | Small-fruited Bulrush | Cyperaceae |
| Scirpus pendulus | Rufous Bulrush | Cyperaceae |
| Scirpus pungens | Chairmaker's Rush | Cyperaceae |
| Scirpus validus | Great Bulrush | Cyperaceae |
| Sclerolepis uniflora | Pink Bogbutton | Asteraceae |
| Scrophularia lanceolata | Early Figwort | Scrophulariaceae |
| Scrophularia marilandica | Maryland Figwort | Scrophulariaceae |
| Scutellaria elliptica | Hairy Skullcap | Lamiaceae |
| Scutellaria epilobiifolia | Marsh Skullcap | Lamiaceae |
| Scutellaria incana | Hoary Skullcap | Lamiaceae |
| Scutellaria lateriflora | Mad-dog Skullcap | Lamiaceae |
| Scutellaria parvula var. leonardii | Small Skullcap | Lamiaceae |
| Scutellaria parvula var. parvula | ||
| Sedum ternatum | Woodland Stonecrop | Crassulaceae |
| Selaginella apoda | Meadow Spikemoss | Selaginellaceae |
| Selaginella rupestris | Rock Spikemoss | Selaginellaceae |
| Senecio aureus | Golden Ragwort | Asteraceae |
| Senecio pauperculus | Balsam Ragwort | Asteraceae |
| Senecio suaveolens | Sweet-scented Indian Plantain | Asteraceae |
| Sericocarpus asteroides | Toothed White-topped Aster | Asteraceae |
| Shepherdia argentea | Silver Buffaloberry | Elaeagnaceae |
| Shepherdia canadensis | Russet Buffaloberry | Elaeagnaceae |
| Sicyos angulatus | Bur Cucumber | Cucurbitaceae |
| Silene regia | Royal Catchfly | Caryophyllaceae |
| Silene stellata | Starry Campion | Caryophyllaceae |
| Silphium integrifolium | Rosinweed | Asteraceae |
| Silphium laciniatum | Compass Plant | Asteraceae |
| Silphium perfoliatum | Cup Plant | Asteraceae |
| Silphium terebinthinaceum | Prairie Dock | Asteraceae |
| Sisyrinchium albidum | Common Blue-Eyed Grass | Iridaceae |
| Sisyrinchium angustifolium | Narrow-leaved Blue-eyed Grass | Iridaceae |
| Sium suave | Hemlock Water Parsnip | Apiaceae |
| Smilax ecirrata | Upright Carrion Flower | Smilacaceae |
| Smilax glauca | Glaucous-leaved Greenbriar | Smilacaceae |
| Smilax hispida | Bristly Greenbrier | Smilacaceae |
| Smilax lasioneura | Carrion Flower | Smilacaceae |
| Smilax rotundifolia | Green Brier | Smilacaceae |
| Solanum carolinense | Horse-nettle | Solanaceae |
| Solanum rostratum | Buffalobur Nightshade | Solanaceae |
| Solidago altissima | Tall Goldenrod | Asteraceae |
| Solidago arguta | Atlantic Goldenrod | Asteraceae |
| Solidago bicolor | Silverrod | Asteraceae |
| Solidago canadensis | Canada Goldenrod | Asteraceae |
| Solidago caesia | Blue-stemmed Goldenrod | Asteraceae |
| Solidago erecta | Slender Goldenrod | Asteraceae |
| Solidago fistulosa | Pine Barren Goldenrod | Asteraceae |
| Solidago flexicaulis | Broad-leaved Goldenrod | Asteraceae |
| Solidago gigantea | Giant Goldenrod | Asteraceae |
| Solidago graminifolia | Grass-leaved Goldenrod | Asteraceae |
| Solidago juncea | Early Goldenrod | Asteraceae |
| Solidago leiocarpa | Alpine Goldenrod | Asteraceae |
| Solidago macrophylla | Large-leaved Goldenrod | Asteraceae |
| Solidago nemoralis | Old-field Goldenrod | Asteraceae |
| Solidago odora | Licorice Goldenrod | Asteraceae |
| Solidago ohioensis | Ohio Goldenrod | Asteraceae |
| Solidago patula | Swamp Goldenrod | Asteraceae |
| Solidago ptarmicoides | Prairie Goldenrod | Asteraceae |
| Solidago puberula | Downy Goldenrod | Asteraceae |
| Solidago riddellii | Riddell's Goldenrod | Asteraceae |
| Solidago rigida | Stiff Goldenrod | Asteraceae |
| Solidago rugosa | Rough Goldenrod | Asteraceae |
| Solidago sempervirens | Seaside Goldenrod | Asteraceae |
| Solidago squarrosa | Stout Goldenrod | Asteraceae |
| Solidago speciosa | Showy Goldenrod | Asteraceae |
| Solidago uliginosa | Bog Goldenrod | Asteraceae |
| Solidago ulmifolia | Elm-leaved Goldenrod | Asteraceae |
| Sorbus americana | American Mountain Ash | Rosaceae |
| Sorbus decora | Showy Mountain Ash | Rosaceae |
| Sorghastrum nutans | Indian Grass | Poaceae |
| Sparganium americanum | American Bur-reed | Sparganiaceae |
| Sparganium angustifolium | Narrow-leaved Bur-reed | Sparganiaceae |
| Sparganium emersum | Unbranched Bur-reed | Sparganiaceae |
| Sparganium eurycarpum | Common Bur-Reed | Sparganiaceae |
| Spartina pectinata | Prairie Cord Grass | Poaceae |
| Sphagnum spp. | Sphagnum moss | Sphagnaceae |
| Spinulum annotinum | Common Bristly Clubmoss | Lycopodiaceae |
| Spiraea alba | Meadowsweet | Rosaceae |
| Spiraea tomentosa | Steeplebush | Rosaceae |
| Spiranthes arcisepala | Appalachian Ladies' Tresses | Orchidaceae |
| Spiranthes bightensis | Atlantic Ladies' Tresses | Orchidaceae |
| Spiranthes casei | Case's Ladies' Tresses | Orchidaceae |
| Spiranthes cernua | Nodding Ladies' Tresses | Orchidaceae |
| Spiranthes incurva | Sphinx Ladies' Tresses | Orchidaceae |
| Spiranthes lacera | Slender Ladies' Tresses | Orchidaceae |
| Spiranthes laciniata | Lace-lipped Ladies' Tresses | Orchidaceae |
| Spiranthes lucida | Shining Ladies' Tresses | Orchidaceae |
| Spiranthes magnicamporum | Great Plains Ladies' Tresses | Orchidaceae |
| Spiranthes ochroleuca | Yellow Ladies' Tresses | Orchidaceae |
| Spiranthes odorata | Fragrant Ladies' Tresses | Orchidaceae |
| Spiranthes ovalis | October Ladies' Tresses | Orchidaceae |
| Spiranthes romanzoffiana | Hooded Ladies' Tresses | Orchidaceae |
| Spiranthes sheviakii | Old Field Ladies' Tresses | Orchidaceae |
| Spiranthes vernalis | Spring Ladies' Tresses | Orchidaceae |
| Sporobolus heterolepsis | Prairie Dropseed | Poaceae |
| Stachys arenicola | Sand Hedge Nettle | Lamiaceae |
| Stachys hispida | Hairy Hedge Nettle | Lamiaceae |
| Stachys tenuifolia | Smooth Hedge Nettle | Lamiaceae |
| Staphylea trifolia | Bladdernut | Staphyleaceae |
| Stellaria longipes | Long-stalked Starwort | Caryophyllaceae |
| Stipa spartea | Porcupine Grass | Poaceae |
| Streptopus amplexifolius | Clasping-leaved Twisted-stalk | Liliaceae |
| Streptopus lanceolatus | Rose Twisted-stalk | Liliaceae |
| Stylophorum diphyllum | Celandine Poppy | Papaveraceae |
| Symphoricarpos albus | Common Snowberry | Caprifoliaceae |
| Symplocarpus foetidus | Skunk Cabbage | Araceae |
| Symphyotrichum boreale | Northern Bog Aster | Asteraceae |
| Symphyotrichum cordifolium | Heart-leaved Aster | Asteraceae |
| Symphyotrichum depauperatum | Serpentine Aster | Asteraceae |
| Symphyotrichum drummondii | Drummond's Aster | Asteraceae |
| Symphyotrichum dumosum | Bushy Aster | Asteraceae |
| Symphyotrichum firmum | Glossy-leaved Aster | Asteraceae |
| Symphyotrichum laeve | Smooth Blue Aster | Asteraceae |
| Symphyotrichum lanceolatum | Lance-leaved Aster | Asteraceae |
| Symphyotrichum lateriflorum | Calico Aster | Asteraceae |
| Symphyotrichum lowrieanum | Lowrie's Blue Wood Aster | Asteraceae |
| Symphyotrichum novae-angliae | New England Aster | Asteraceae |
| Symphyotrichum novi-belgii | New York Aster | Asteraceae |
| Symphyotrichum oblongifolium | Aromatic Aster | Asteraceae |
| Symphyotrichum oolentangiense | Sky Blue Aster | Asteraceae |
| Symphyotrichum patens | Late Purple Aster | Asteraceae |
| Symphyotrichum pilosum | Hairy White Aster | Asteraceae |
| Symphyotrichum prenanthoides | Crooked-stemmed Aster | Asteraceae |
| Symphyotrichum puniceum | Purple-stemmed Aster | Asteraceae |
| Symphyotrichum shortii | Short's Aster | Asteraceae |
| Symphyotrichum undulatum | Wavy-leaved Aster | Asteraceae |
| Symphyotrichum urophyllum | White Arrow-leaved Aster | Asteraceae |
© 2004 Michael Hough