| § Ratibida columnifera |  Mexican Hat, Coneflower |
| § Rhus lanceolata | Lanceleaf Sumac |
| § Rhus microphylla | Littleleaf Sumac, Squawberry |
| § Rhus trilobata | Aromatic Sumac, Limitas |
| § Rhus virens var. choriophylla | Evergreen Sumac |
| § Ribes aureum | Golden Current |
| § Rivina humilis | Rouge Plant, Pigeon Berry |
| § Rumex hymenosepalus | Dock, Sorrel, Canaigre |
| § Salazaria mexicana | Bladder Sage |
| § Salix exigua | Coyote Willow |
| Salix gooddingii | Goodding Willow |
| § Salvia chamaedryoides | Mexican Blue Sage |
| § Salvia farinacea | Mealy Cup Sage, "Texas Violet" |
| § Salvia greggii | Cherry Sage, Autumn Sage |
| § Salvia leptophylla | Slenderleaf Sage |
| § Salvia lycioides | Blue Canyon Sage |
| § Salvia microphylla | Red Canyon Sage |
| § Salvia penstemonoides | Big Red Sage |
| § Salvia pinguifolia | Rock Sage |
| § Salvia regla | Mountain Sage |
| § Salvia roemeriana | Cedar Sage |
| Salvia spathecifolia | Tarahumara Sage |
| § Salvia summa | Summa Sage |
| § Sapindus saponaria var. drummondi | Western Soapberry, Jaboncillo |
| § Sarcostemma cynanchoides | Twining Milkweed |
| § Schaefferia cuneifolia | Desert Yaupon, Capul, Panalero |
| § Sclerocactus intertexta | White Fishook Cactus |
| § Sclerocactus uncinatus | Chihuahuan Fishook Cactus |
| § Scutellaria suffrutescens | Red Skullcap |
| § Scutellaria wrightii | Blue Skullcap |
| § Selaginella lepidophylla | Resurrection Plant |
| § Selaginella sp. | Resurrection Plant |
| Selinocarpus diffusus | Moonpod |
| § Senecio flaccidus | Threadleaf Groundsel, Gordolobos |
| § Senecio riddellii | Sand Groundsel |
| § Senna bauhinioides | Twinleaf Cassia |
| § Senna lindheimeriana | Velvetleaf Cassia |
| § Senna roemeriana | Twoleaf Cassia |
| § Senna wislizenii | Shrubby Senna |
| § Sida abutifolia | Spreading Fanpetals |
| § Silene laciniata | Mexican Campion |
| § Solanum elaeagnifolium | Silverleaf Nightshade |
| § Solanum rostratum | Buffalobur Nightshade |
| § Sophora secundiflora | Texas Mountain Laurel, Mescal Bean |
| § Sphaeralcea angustifolia | Narrowleaf Globemallow |
| § Sphaeralcea coccinea | Globe Mallow |
| § Sphaeralcea digitata | Juniper Globemallow |
| § Sphaeralcea fendleri | Fendler's Globemallow |
| § Sphaeralcea incana | Gray Globe Mallow |
| Sporobolus airoides | Alkali Sacaton |
| § Sporobolus cryptandrus | Sand Dropseed |
| § Sporobolus wrightii | Giant Sacaton |
| § Stachys coccinea | Scarlet Hedgenettle |
| § Stanleya pinnata | Prince's Plume |
| Stipa tenuissima | Needle Grass |
| § Streptanthus carinatus | Lyreleaf Jewelflower |
Last Update: 8 Oct 2006