Rocky Mountain zinnia (Zinnia grandiflora) romero macho (Pectis linifolia) rose heath (Leucelene ericoides) Rothrock's knapweed (Centaurea rothrockii) Rothrock's snakeroot (Ageratina rothrockii) rough blackfoot (Melampodium sericeum) rough cocklebur (Xanthium strumarium) rubber rabbitbrush (Ericameria nauseosa) running fleabane (Erigeron tracyi) Rusby's cinchweed (Pectis rusbyi) Rusby's hawkweed (Hieracium abscissum) Rutter's false goldenaster (Heterotheca rutteri) safflower (Carthamus tinctorius) San Diego sunflower (Bahiopsis laciniata) San Diego wirelettuce (Stephanomeria diegensis) San Pedro daisy (Lasianthaea podocephala) Santa Maria feverfew (Parthenium hysterophorus) Santa Rita Mountain aster (Symphyotrichum potosinum) Santa Rita snakeroot (Ageratina paupercula) sawtooth candyleaf (Stevia serrata) scalebud (Anisocoma acaulis) scepterbearing fleabane (Erigeron sceptrifer) Schott's pygmycedar (Peucephyllum schottii) Seeman's sunbonnets (Leibnitzia lyrata) shaggy blackfoot (Melampodium strigosum) shaggy soldier (Galinsoga quadriradiata) shortleaf baccharis (Baccharis brachyphylla) shortray rockdaisy (Perityle microglossa) showy sunflower (Helianthus niveus) shrine jimmyweed (Isocoma tenuisecta) shrubby thoroughwort (Koanophyllon solidaginifolium) Siam weed (Chromolaena odorata) singlewhorl burrobrush (Hymenoclea monogyra) slender poreleaf (Porophyllum gracile) slimleaf bursage (Ambrosia confertiflora) slimlobe beggarticks (Bidens tenuisecta) smallflower desert-chicory (Pyrrhopappus pauciflorus) smallflower tansyaster (Machaeranthera parviflora) small wirelettuce (Stephanomeria exigua) smooth beggarticks (Bidens laevis) smooth desertdandelion (Malacothrix glabrata) snake's head (Malacothrix coulteri) Sonoran brickellbush (Brickellia simplex) Sonoran bursage (Ambrosia cordifolia) Sonoran cinchweed (Pectis cylindrica) Sonoran desertdandelion (Malacothrix sonorae) Sonoran neststraw (Stylocline sonorensis) Sonoran pricklyleaf (Thymophylla concinna) Sonoran thoroughwort (Fleischmannia sonorae) southern annual saltmarsh aster (Symphyotrichum divaricatum) southern goldenbush (Isocoma pluriflora) southwestern cosmos (Cosmos parviflorus) Spanish needles (Bidens alba) spearleaf brickellbush (Brickellia atractyloides) spineless horsebrush (Tetradymia canescens) spiny chloracantha (Chloracantha spinosa) spiny sowthistle (Sonchus asper) spoonleaf purple everlasting (Gamochaeta purpurea) spreading cinchweed (Pectis prostrata) spreading fleabane (Erigeron divergens) spring pygmy-cudweed (Diaperia verna) Stebbins' desertdandelion (Malacothrix stebbinsii) stemless four-nerve daisy (Tetraneuris acaulis) sticky brittlebush (Encelia resinifera) stinking brickellbush (Brickellia rusbyi) straggler daisy (Calyptocarpus vialis) sulphur cosmos (Cosmos sulphureus) sweetbush (Bebbia juncea) Tahoka daisy (Machaeranthera tanacetifolia) tarragon (Artemisia dracunculus) tasselflower brickellbush (Brickellia grandiflora) Texas blueweed (Helianthus ciliaris) threadleaf ragwort (Senecio flaccidus) threadleaf snakeweed (Gutierrezia microcephala) Thurber's desertpeony (Acourtia thurberi) Thurber's sneezeweed (Helenium thurberi) Thurber's wirelettuce (Stephanomeria thurberi) toothleaf goldeneye (Viguiera dentata) trailing fleabane (Erigeron flagellaris) Trans-Pecos thimblehead (Hymenothrix wislizeni) triangle-leaf bursage (Ambrosia deltoidea) turpentine bush (Ericameria laricifolia) upright prairie coneflower (Ratibida columnifera) veiny brickellbush (Brickellia venosa) velvet turtleback (Psathyrotes ramosissima) veronicaleaf brickellbush (Brickellia veronicifolia) Virgin River brittlebush (Encelia virginensis) viscid candyleaf (Stevia viscida) Wallace's woolly daisy (Eriophyllum wallacei) western pearly everlasting (Anaphalis margaritacea) white cudweed (Pseudognaphalium leucocephalum) whitedaisy tidytips (Layia glandulosa) whitemargin pussytoes (Antennaria marginata) white sagebrush (Artemisia ludoviciana) whitestem paperflower (Psilostrophe cooperi) white tackstem (Calycoseris wrightii) white woolly daisy