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Plant List
Indexed Alphabetically by Common Name
T, U, V, W, X, Y & Z
For a list of plants indexed by Scientific Name, click here
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| National Common Name | Scientific Name with Author | Symbol | Family | |
| tabardillo | Calliandra californica Benth. | CACA82 | Fabaceae | |
| tachibana orange | Citrus tachibana (Makino) T. Tanaka | CITA3 | Rutaceae | |
| tackstem | Calycoseris Gray | CALYC4 | Asteraceae | |
| tagasaste | Chamaecytisus palmensis (Christ) Bisby & K. Nicholls [excluded] | CHPA44 | Fabaceae | |
| Tahoe sedge | Carex tahoensis Smiley | CATA | Cyperaceae | |
| tail grape | Artabotrys R. Br. | ARTAB | Annonaceae | |
| tailed grapefern | Botrychium acuminatum W.H. Wagner | BOAC2 | Ophioglossaceae | |
| tailed maidenhair | Adiantum caudatum L. | ADCA3 | Pteridaceae | |
| tailed nicker | Caesalpinia caudata (Gray) Fisher | CACA26 | Fabaceae | |
| tailed strapfern | Campyloneurum costatum (Kunze) K. Presl | CACO20 | Polypodiaceae | |
| talayote | Cynanchum racemosum (Jacq.) Jacq. | CYRA4 | Asclepiadaceae | |
| talayote | Cynanchum racemosum (Jacq.) Jacq. var. unifarium (Scheele) E. Sundell | CYRAU | Asclepiadaceae | |
| talh | Acacia seyal Del. | ACSE7 | Fabaceae | |
| tall agoseris | Agoseris elata (Nutt.) Greene | AGEL | Asteraceae | |
| tall albizia | Albizia procera (Roxb.) Benth. | ALPR | Fabaceae | |
| tall baeckea | Baeckea virgata (J.R. Forst. & G. Forst.) Andrews | BAVI9 | Myrtaceae | |
| tall beardgrass | Bothriochloa alta (A.S. Hitchc.) Henr. | BOAL3 | Poaceae | |
| tall brome | Bromus grandis (Shear) A.S. Hitchc. | BRGR4 | Poaceae | |
| tall bugbane | Actaea elata (Nutt.) Prantl | ACEL4 | Ranunculaceae | |
| tall chamomile | Anthemis altissima L. | ANAL11 | Asteraceae | |
| tall dodder | Cuscuta exaltata Engelm. | CUEX | Cuscutaceae | |
| tall false foxglove | Agalinis aspera (Dougl. ex Benth.) Britt. | AGAS2 | Scrophulariaceae | |
| tall flatsedge | Cyperus eragrostis Lam. | CYER | Cyperaceae | |
| tall grama | Bouteloua hirsuta Lag. var. pectinata (Featherly) Cory | BOHIP | Poaceae | |
| tall hairy agrimony | Agrimonia gryposepala Wallr. | AGGR2 | Rosaceae | |
| tall ladies'-tresses | Cyclopogon elatus (Sw.) Schlechter | CYEL6 | Orchidaceae | |
| tall milkvetch | Astragalus altus Woot. & Standl. | ASAL8 | Fabaceae | |
| tall oat grass | Arrhenatherum album (Vahl) Clayton | ARAL28 | Poaceae | |
| tall oatgrass | Arrhenatherum elatius (L.) Beauv. ex J.& K. Presl | AREL3 | Poaceae | |
| tall oatgrass | Arrhenatherum elatius (L.) Beauv. ex J.& K. Presl var. bulbosum (Willd.) Spenner | ARELB | Poaceae | |
| tall oatgrass | Arrhenatherum elatius (L.) Beauv. ex J.& K. Presl var. elatius | ARELE | Poaceae | |
| tall poppymallow | Callirhoe leiocarpa R.F. Martin | CALE2 | Malvaceae | |
| tall silverbush | Argythamnia mercurialina (Nutt.) Muell.-Arg. | ARME5 | Euphorbiaceae | |
| tall silverbush | Argythamnia mercurialina (Nutt.) Muell.-Arg. var. mercurialina | ARMEM | Euphorbiaceae | |
| tall silverbush | Argythamnia mercurialina (Nutt.) Muell.-Arg. var. pilosissima (Benth.) Shinners | ARMEP | Euphorbiaceae | |
| tall spiny milkvetch | Astragalus kentrophyta Gray var. elatus S. Wats. | ASKEE | Fabaceae | |
| tall spiritweed | Aegiphila elata Sw. | AEEL | Verbenaceae | |
| tall thimbleweed | Anemone virginiana L. | ANVI3 | Ranunculaceae | |
| tall thimbleweed | Anemone virginiana L. var. alba (Oakes) Wood | ANVIA2 | Ranunculaceae | |
| tall thimbleweed | Anemone virginiana L. var. cylindroidea Boivin | ANVIC | Ranunculaceae | |
| tall thimbleweed | Anemone virginiana L. var. virginiana | ANVIV2 | Ranunculaceae | |
| tall thistle | Cirsium altissimum (L.) Hill | CIAL2 | Asteraceae | |
| tall threeawn | Aristida patula Chapman ex Nash | ARPA11 | Poaceae | |
| tall tickseed | Coreopsis tripteris L. | COTR4 | Asteraceae | |
| tall windmill grass | Chloris elata Desv. | CHEL3 | Poaceae | |
| Tallahassee hawthorn | Crataegus consanguinea Beadle | CRCO8 | Rosaceae | |
| Tallul campylopus moss | Campylopus tallulensis Sull. & Lesq. | CATA4 | Dicranaceae | |
| talus collomia | Collomia larsenii (Gray) Payson | COLA8 | Polemoniaceae | |
| talus springparsley | Cymopterus lapidosus (M.E. Jones) M.E. Jones | CYLA10 | Apiaceae | |
| tamarind anisomeridium lichen | Anisomeridium tamarindi (Fee) R. C. Harris | ANTA2 | Monoblastiaceae | |
| tangelo | Citrus ×tangelo J. Ingram & H. Moore | CITA | Rutaceae | |
| tangerine | Citrus reticulata Blanco | CIRE3 | Rutaceae | |
| tangor | Citrus nobilis Lour. | CINO3 | Rutaceae | |
| Tanners Canyon onion | Allium plummerae S. Wats. | ALPL4 | Liliaceae | |
| tansyleaf evening-primrose | Camissonia tanacetifolia (Torr. & Gray) Raven | CATA2 | Onagraceae | |
| tansyleaf evening-primrose | Camissonia tanacetifolia (Torr. & Gray) Raven ssp. tanacetifolia | CATAT | Onagraceae | |
| taperfruit shortscale sedge | Carex leptopoda Mackenzie | CALE24 | Cyperaceae | |
| tapertip dodder | Cuscuta attenuata Waterfall | CUAT | Cuscutaceae | |
| tapertip flatsedge | Cyperus acuminatus Torr. & Hook. ex Torr. | CYAC2 | Cyperaceae | |
| tapertip hawksbeard | Crepis acuminata Nutt. | CRAC2 | Asteraceae | |
| tapertip hawksbeard | Crepis acuminata Nutt. ssp. acuminata | CRACA | Asteraceae | |
| tapertip hawksbeard | Crepis acuminata Nutt. ssp. pluriflora Babcock & Stebbins | CRACP | Asteraceae | |
| tapertip onion | Allium acuminatum Hook. | ALAC4 | Liliaceae | |
| tapertip spleenwort | Asplenium acuminatum Hook. & Arn. | ASAC4 | Aspleniaceae | |
| tara vine | Actinidia arguta (Sieb. & Zucc.) Planch. ex Miq. | ACAR10 | Actinidiaceae | |
| tarflower | Bejaria racemosa Vent. | BERA3 | Ericaceae | |
| tarheel sedge | Carex austrocaroliniana Bailey | CAAU7 | Cyperaceae | |
| Tarheel sedge | Carex pigra Naczi | CAPI21 | Cyperaceae | |
| taro | Alocasia (Schott) G. Don | ALOCA | Araceae | |
| tarragon | Artemisia dracunculus L. | ARDR4 | Asteraceae | |
| tarweed fiddleneck | Amsinckia lycopsoides Lehm. | AMLY | Boraginaceae | |
| tasselflower brickellbush | Brickellia grandiflora (Hook.) Nutt. | BRGR | Asteraceae | |
| Tatarian aster | Aster tataricus L. f. | ASTA | Asteraceae | |
| Tatarian cephalaria | Cephalaria gigantea (Ledeb.) Bobr. | CEGI2 | Dipsacaceae | |
| tatarian maple | Acer tataricum L. | ACTA80 | Aceraceae | |
| Tatarian orache | Atriplex tatarica L. | ATTA | Chenopodiaceae | |
| Tausch's goatgrass | Aegilops tauschii Coss. | AETA2 | Poaceae | |
| tawny cryptantha | Cryptantha fulvocanescens (S. Wats.) Payson | CRFU | Boraginaceae | |
| tawny cryptantha | Cryptantha fulvocanescens (S. Wats.) Payson var. fulvocanescens | CRFUF | Boraginaceae | |
| tawny cryptantha | Cryptantha fulvocanescens (S. Wats.) Payson var. nitida (Greene) R.C. Sivinski | CRFUN | Boraginaceae | |
| tea | Camellia sinensis (L.) Kuntze var. sinensis | CASIS3 | Theaceae | |
| tea | Camellia sinensis (L.) O. Kuntze | CASI16 | Theaceae | |
| tecate cypress | Cupressus forbesii Jepson | CUFO2 | Cupressaceae | |
| Tecopa bird's beak | Cordylanthus tecopensis Munz & Roos | COTE2 | Scrophulariaceae | |
| teddybear cholla | Cylindropuntia bigelovii (Engelm.) F.M. Knuth | CYBI9 | Cactaceae | |
| Tejon cryptantha | Cryptantha microstachys (Greene ex Gray) Greene | CRMI3 | Boraginaceae | |
| telegraph-plant | Codariocalyx motorius (Houtt.) H. Ohashi | COMO13 | Fabaceae | |
| Temblor Range clarkia | Clarkia tembloriensis Vasek | CLTE5 | Onagraceae | |
| Temblor Range clarkia | Clarkia tembloriensis Vasek ssp. tembloriensis | CLTET | Onagraceae | |
| tender green | Brassica perviridis (L. H. Bailey) L. H. Bailey | BRPE3 | Brassicaceae | |
| Tenerife white marguerite | Argyranthemum gracilis Webb ex Sch. Bip. | ARGR20 | Asteraceae | |
| tenlobe false foxglove | Agalinis obtusifolia Raf. | AGOB | Scrophulariaceae | |
| Tennessee milkvetch | Astragalus tennesseensis Gray ex Chapman | ASTE7 | Fabaceae | |
| tenpetal thimbleweed | Anemone berlandieri Pritz. | ANBE | Ranunculaceae | |
| tequila agave | Agave tequilana A. Weber | AGTE7 | Agavaceae | |
| Terlingu brickellia | Brickellia hinckleyi Standl. var. terlinguensis (Flyr) B.L. Turner | BRHIT | Asteraceae | |
| Terlingua Creek cryptantha | Cryptantha crassipes I.M. Johnston | CRCR7 | Boraginaceae | |
| Terlingua sandmat | Chamaesyce theriaca (L.C. Wheeler) Shinners | CHTH6 | Euphorbiaceae | |
| ternate grapefern | Botrychium rugulosum W.H. Wagner | BORU | Ophioglossaceae | |
| terrestrial water-starwort | Callitriche terrestris Raf. | CATE19 | Callitrichaceae | |
| teta prieta | Cleyera albopunctata (Griseb.) Krug & Urban | CLAL4 | Theaceae | |
| Teton anemone | Anemone tetonensis Porter ex Britt. | ANTE3 | Ranunculaceae | |
| Texan canoparmelia lichen | Canoparmelia texana (Tuck.) Elix & Hale | CATE22 | Parmeliaceae | |
| Texan flatsedge | Cyperus polystachyos Rottb. var. texensis (Torr.) Fern. | CYPOT | Cyperaceae | |
| Texan fumewort | Corydalis micrantha (Engelm. ex Gray) Gray ssp. texensis G.B. Ownbey | COMIT2 | Fumariaceae | |
| Texan goatbush | Castela erecta Turp. ssp. texana (Torr. & Gray) Cronq. | CAERT | Simaroubaceae | |
| Texan great ragweed | Ambrosia trifida L. var. texana Scheele | AMTRT | Asteraceae | |
| Texan hogplum | Colubrina texensis (Torr. & Gray) Gray | COTE6 | Rhamnaceae | |
| Texan hogplum | Colubrina texensis (Torr. & Gray) Gray var. pedunculata M.C. Johnston | COTEP | Rhamnaceae | |
| Texan hogplum | Colubrina texensis (Torr. & Gray) Gray var. texensis | COTET | Rhamnaceae | |
| Texan sugarberry | Celtis laevigata Willd. var. texana Sarg. | CELAT8 | Ulmaceae | |
| Texas babybonnets | Coursetia axillaris Coult. & Rose | COAX | Fabaceae | |
| Texas bergia | Bergia texana (Hook.) Seub. ex Walp. | BETE | Elatinaceae | |
| Texas bindweed | Convolvulus equitans Benth. | COEQ | Convolvulaceae | |
| Texas bittercress | Cardamine macrocarpa Brandeg. var. texana Rollins | CAMAT | Brassicaceae | |
| Texas bluestar | Amsonia ciliata Walt. var. texana (Gray) Coult. | AMCIT2 | Apocynaceae | |
| Texas brome | Bromus texensis (Shear) A.S. Hitchc. | BRTE2 | Poaceae | |
| Texas broomweed | Amphiachyris amoena (Shinners) Solbrig | AMAM3 | Asteraceae | |
| Texas bruchia moss | Bruchia texana Aust. | BRTE7 | Bruchiaceae | |
| Texas bullnettle | Cnidoscolus texanus (Muell.-Arg.) Small | CNTE | Euphorbiaceae | |
| Texas chickweed | Cerastium texanum Britt. | CETE3 | Caryophyllaceae | |
| Texas chrysopsis | Chrysopsis texana Nesom | CHTE10 | Asteraceae | |
| Texas croton | Croton texensis (Klotzsch) Muell.-Arg. | CRTE4 | Euphorbiaceae | |
| Texas croton | Croton texensis (Klotzsch) Muell.-Arg. var. texensis | CRTET | Euphorbiaceae | |
| Texas dutchman's pipe | Aristolochia reticulata Jacq. | ARRE3 | Aristolochiaceae | |
| Texas flatsedge | Cyperus seslerioides Kunth | CYSE2 | Cyperaceae | |
| Texas gourd | Cucurbita pepo L. var. texana (Scheele) D. Decker | CUPET | Cucurbitaceae | |
| Texas grama | Bouteloua rigidiseta (Steud.) A.S. Hitchc. | BORI | Poaceae | |
| Texas greeneyes | Berlandiera betonicifolia (Hook.) Small | BEBE4 | Asteraceae | |
| Texas hawthorn | Crataegus texana Buckl. | CRTE2 | Rosaceae | |
| Texas Indian mallow | Abutilon fruticosum Guill. & Perrottet | ABFR3 | Malvaceae | |
| Texas Indian paintbrush | Castilleja foliolosa Hook. & Arn. | CAFO2 | Scrophulariaceae | |
| Texas jelly lichen | Collema texanum Tuck. | COTE14 | Collemataceae | |
| Texas madeiravine | Anredera vesicaria (Lam.) Gaertn. f. | ANVE2 | Basellaceae | |
| Texas madrone | Arbutus xalapensis Kunth | ARXA80 | Ericaceae | |
| Texas manjack | Cordia podocephala Torr. | COPO2 | Boraginaceae | |
| Texas milkweed | Asclepias texana Heller | ASTE | Asclepiadaceae | |
| Texas poppymallow | Callirhoe scabriuscula B.L. Robins. | CASC4 | Malvaceae | |
| Texas pricklypoppy | Argemone aurantiaca G.B. Ownbey | ARAU2 | Papaveraceae | |
| Texas redbud | Cercis canadensis L. var. texensis (S. Wats.) M. Hopkins | CECAT | Fabaceae | |
| Texas ringstem | Anulocaulis reflexus I.M. Johnston | ANRE3 | Nyctaginaceae | |
| Texas salt | Allolepis Söderstrom & Decker | ALLOL | Poaceae | |
| Texas salt | Allolepis texana (Vasey) Söderstrom & Decker | ALTE3 | Poaceae | |
| Texas saltbush | Atriplex texana S. Wats. | ATTE2 | Chenopodiaceae | |
| Texas saucerflower | Antiphytum floribundum (Torr.) Gray | ANFL3 | Boraginaceae | |
| Texas screwstem | Bartonia texana Correll | BATE2 | Gentianaceae | |
| Texas sedge | Carex texensis (Torr.) Bailey | CATE7 | Cyperaceae | |
| Texas sensitive pea | Chamaecrista flexuosa (L.) Greene | CHFL4 | Fabaceae | |
| Texas sensitive pea | Chamaecrista flexuosa (L.) Greene var. texana (Buckl.) Irwin & Barneby | CHFLT | Fabaceae | |
| Texas shell lichen | Arthopyrenia texensis (Cooke) D. Hawksw. | ARTE12 | Arthopyreniaceae | |
| Texas sundrops | Calylophus tubicula (Gray) Raven | CATU6 | Onagraceae | |
| Texas thistle | Cirsium texanum Buckl. | CITE2 | Asteraceae | |
| Texas tickseed | Coreopsis linifolia Nutt. | COLI5 | Asteraceae | |
| Texas torchwood | Amyris texana (Buckl.) P. Wilson | AMTE4 | Rutaceae | |
| Texas trumpets | Acleisanthes crassifolia Gray | ACCR | Nyctaginaceae | |
| Texas western daisy | Astranthium robustum (Shinners) DeJong | ASRO2 | Asteraceae | |
| Texas windmill grass | Chloris texensis Nash | CHTE | Poaceae | |
| Texas wrightwort | Carlowrightia texana Henrickson & Daniel | CATE15 | Acanthaceae | |
| Texasplume | Bauhinia lunarioides Gray ex S. Wats. | BALU | Fabaceae | |
| textile bamboo | Bambusa textilis McClure | BATE6 | Poaceae | |
| textile onion | Allium textile A. Nels. & J.F. Macbr. | ALTE | Liliaceae | |
| Tharp's croton | Croton lindheimerianus Scheele var. tharpii M.C. Johnston | CRLIT | Euphorbiaceae | |
| The Cedars manzanita | Arctostaphylos bakeri Eastw. ssp. sublaevis P.V. Wells | ARBAS | Ericaceae | |
| thicket anoda | Anoda crenatiflora Ortega | ANCR | Malvaceae | |
| thicket hogwood | Clidemia strigillosa (Sw.) DC. | CLST2 | Melastomataceae | |
| thicket rattlebox | Crotalaria virgulata Klotzsch | CRVI14 | Fabaceae | |
| thicket sedge | Carex abscondita Mackenzie | CAAB5 | Cyperaceae | |
| thickfoot saltbush | Atriplex pachypoda Stutz & Chu | ATPA8 | Chenopodiaceae | |
| thickhead sedge | Carex macloviana d'Urv. | CAMA9 | Cyperaceae | |
| thickpod milkvetch | Astragalus pachypus Greene | ASPA9 | Fabaceae | |
| thickpod milkvetch | Astragalus pachypus Greene var. pachypus | ASPAP5 | Fabaceae | |
| thicksepal cryptantha | Cryptantha crassisepala (Torr. & Gray) Greene | CRCR3 | Boraginaceae | |
| thicksepal cryptantha | Cryptantha crassisepala (Torr. & Gray) Greene var. crassisepala | CRCRC | Boraginaceae | |
| thicksepal cryptantha | Cryptantha crassisepala (Torr. & Gray) Greene var. elachantha I.M. Johnston | CRCRE | Boraginaceae | |
| thickstem wild cabbage | Caulanthus crassicaulis (Torr.) S. Wats. | CACR11 | Brassicaceae | |
| thickstem wild cabbage | Caulanthus crassicaulis (Torr.) S. Wats. var. crassicaulis | CACRC | Brassicaceae | |
| thickstem wild cabbage | Caulanthus crassicaulis (Torr.) S. Wats. var. glaber M.E. Jones | CACRG | Brassicaceae | |
| Thiers' cup lichen | Cladonia thiersii S. Hammer | CLTH2 | Cladoniaceae | |
| thinfruit sedge | Carex flaccosperma Dewey | CAFL3 | Cyperaceae | |
| thinleaf alder | Alnus incana (L.) Moench ssp. tenuifolia (Nutt.) Breitung | ALINT | Betulaceae | |
| thinleaf creepingfern | Bolbitis nicotianifolia (Sw.) Alston | BONI | Dryopteridaceae | |
| thinleaf false brome | Brachypodium phoenicoides (L.) Roemer & J.A. Schultes | BRPH3 | Poaceae | |
| thinleaf fourwing saltbush | Atriplex canescens (Pursh) Nutt. var. linearis (S. Wats.) Munz | ATCAL4 | Chenopodiaceae | |
| thinleaf sedge | Carex cephaloidea (Dewey) Dewey | CACE2 | Cyperaceae | |
| thinstem lady's mantle | Alchemilla filicaulis Buser | ALFI5 | Rosaceae | |
| thinstem lady's mantle | Alchemilla filicaulis Buser ssp. vestita (Buser) M.E. Bradshaw | ALFIV | Rosaceae | |
| thistle | Cirsium P. Mill. | CIRSI | Asteraceae | |
| thistle cholla | Cylindropuntia davisii (Engelm. & Bigelow) F.M. Knuth | CYDA4 | Cactaceae | |
| thistle cholla | Cylindropuntia tunicata (Lehm.) F.M. Knuth | CYTU3 | Cactaceae | |
| Thomas' lidflower | Calyptranthes thomasiana Berg | CATH3 | Myrtaceae | |
| Thompkins' sedge | Carex tompkinsii J.T. Howell | CATO9 | Cyperaceae | |
| Thompson's cryptantha | Cryptantha thompsonii I.M. Johnston | CRTH3 | Boraginaceae | |
| Thompson's Indian paintbrush | Castilleja thompsonii Pennell | CATH4 | Scrophulariaceae | |
| Thompson's pincushion | Chaenactis thompsonii Cronq. | CHTH | Asteraceae | |
| Thompson's rockcress | Arabis microphylla Nutt. var. thompsonii Rollins | ARMIT | Brassicaceae | |
| Thompson's sandwort | Arenaria franklinii Dougl. ex Hook. var. thompsonii M.E. Peck | ARFRT | Caryophyllaceae | |
| Thomson's cup lichen | Cladonia thomsonii Ahti | CLTH60 | Cladoniaceae | |
| thorn wattle | Acacia continua Benth. | ACCO18 | Fabaceae | |
| Thornber's buckhorn cholla | Cylindropuntia acanthocarpa (Engelm. & Bigelow) F.M. Knuth var. thornberi (Thornb. & Bonker) Pinkava | CYACT | Cactaceae | |
| thorncrest century plant | Agave univittata Haw. | AGUN2 | Agavaceae | |
| thorn-mint | Acanthomintha (Gray) Gray | ACANT2 | Lamiaceae | |
| thoroughwort | Chromolaena DC. | CHROM3 | Asteraceae | |
| thoroughwort | Conoclinium DC. | CONOC4 | Asteraceae | |
| thoroughwort | Critonia P. Br. | CRITO2 | Asteraceae | |
| threadleaf brodiaea | Brodiaea filifolia S. Wats. | BRFI | Liliaceae | |
| threadleaf false foxglove | Agalinis setacea (J.F. Gmel.) Raf. | AGSE3 | Scrophulariaceae | |
| threadleaf giant hyssop | Agastache rupestris (Greene) Standl. | AGRU | Lamiaceae | |
| threadleaf sedge | Carex filifolia Nutt. | CAFI | Cyperaceae | |
| threadstalk milkvetch | Astragalus speirocarpus Gray | ASSP7 | Fabaceae | |
| threadstem sandmat | Chamaesyce revoluta (Engelm.) Small | CHRE4 | Euphorbiaceae | |
| threeawn | Aristida L. | ARIST | Poaceae | |
| threeblossom lidflower | Calyptranthes triflora Alain | CATR12 | Myrtaceae | |
| threebract onion | Allium tribracteatum Torr. | ALTR2 | Liliaceae | |
| threecorner leek | Allium triquetrum L. | ALTR4 | Liliaceae | |
| threeflower hawthorn | Crataegus triflora Chapman | CRTR2 | Rosaceae | |
| threeleaf cayratia | Cayratia trifolia (L.) Domin | CATR29 | Vitaceae | |
| threeleaf goldthread | Coptis trifolia (L.) Salisb. | COTR2 | Ranunculaceae | |
| threelobe beggarticks | Bidens tripartita L. | BITR | Asteraceae | |
| threelocule corchorus | Corchorus trilocularis L. | COTR13 | Tiliaceae | |
| threeseed croton | Croton lindheimerianus Scheele | CRLI2 | Euphorbiaceae | |
| threeseed croton | Croton lindheimerianus Scheele var. lindheimerianus | CRLIL | Euphorbiaceae | |
| threeseeded sedge | Carex trisperma Dewey | CATR10 | Cyperaceae | |
| threeseeded sedge | Carex trisperma Dewey var. trisperma | CATRT3 | Cyperaceae | |
| threespike fiddlewood | Citharexylum tristachyum Turcz. | CITR7 | Verbenaceae | |
| threetip sagebrush | Artemisia tripartita Rydb. | ARTR4 | Asteraceae | |
| threetip sagebrush | Artemisia tripartita Rydb. ssp. tripartita | ARTRT2 | Asteraceae | |
| thrift seapink | Armeria maritima (P. Mill.) Willd. | ARMA6 | Plumbaginaceae | |
| Thule arctopeltis lichen | Arctopeltis thuleana Poelt | ARTH3 | Lecanoraceae | |
| Thunberg's amaranthus | Amaranthus thunbergii Moq. | AMTH2 | Amaranthaceae | |
| Thurber's desert honeysuckle | Anisacanthus thurberi (Torr.) Gray | ANTH2 | Acanthaceae | |
| Thurber's desertpeony | Acourtia thurberi (Gray) Reveal & King | ACTH | Asteraceae | |
| Thurber's Indian mallow | Abutilon thurberi Gray | ABTH2 | Malvaceae | |
| Thurber's milkvetch | Astragalus thurberi Gray | ASTH | Fabaceae | |
| Thurber's needlegrass | Achnatherum thurberianum (Piper) Barkworth | ACTH7 | Poaceae | |
| Thurber's sedge | Carex thurberi Dewey | CATH | Cyperaceae | |
| thymeleaf sandmat | Chamaesyce serpyllifolia (Pers.) Small | CHSE6 | Euphorbiaceae | |
| thymeleaf sandmat | Chamaesyce serpyllifolia (Pers.) Small ssp. hirtella (Engelm. ex S. Wats.) Koutnik | CHSEH | Euphorbiaceae | |
| thymeleaf sandmat | Chamaesyce serpyllifolia (Pers.) Small ssp. serpyllifolia | CHSES | Euphorbiaceae | |
| thymeleaf sandwort | Arenaria serpyllifolia L. | ARSE2 | Caryophyllaceae | |
| ti ngahere | Cordyline banksii Hook. f. | COBA14 | Liliaceae | |
| Tibet milkvetch | Astragalus tibetanus Benth. ex Bunge | ASTI5 | Fabaceae | |
| Tibetan hazelnut | Corylus ferox Wallich var. thibetica (Batalin) Franchet | COFET | Betulaceae | |
| tibey de cresta | Columnea ambigua (Urban) Morley | COAM6 | Gesneriaceae | |
| tibey parasito | Columnea scandens L. | COSC11 | Gesneriaceae | |
| tibey parasito | Columnea scandens L. var. tulae (Urban) Wiehler | COSCT | Gesneriaceae | |
| Tiburon Indian paintbrush | Castilleja affinis Hook. & Arn. ssp. neglecta (Zeile) Chuang & Heckard | CAAFN2 | Scrophulariaceae | |
| Tiburon mariposa lily | Calochortus tiburonensis A.J. Hill | CATI3 | Liliaceae | |
| tick trefoil | Codariocalyx Hassk. | CODAR | Fabaceae | |
| tickseed | Coreopsis L. | COREO2 | Asteraceae | |
| tidalmarsh amaranth | Amaranthus cannabinus (L.) Sauer | AMCA2 | Amaranthaceae | |
| tidalmarsh flatsedge | Cyperus serotinus Rottb. | CYSE5 | Cyperaceae | |
| Tidestrom's milkvetch | Astragalus tidestromii (Rydb.) Clokey | ASTI | Fabaceae | |
| Tiehm's milkvetch | Astragalus tiehmii Barneby | ASTI3 | Fabaceae | |
| tietongue | Coccoloba diversifolia Jacq. | CODI8 | Polygonaceae | |
| Tilesius' wormwood | Artemisia tilesii Ledeb. | ARTI | Asteraceae | |
| Tilesius' wormwood | Artemisia tilesii Ledeb. ssp. elatior (Torr. & Gray) Hultén | ARTIE | Asteraceae | |
| Tilesius' wormwood | Artemisia tilesii Ledeb. ssp. gormanii (Rydb.) Hultén | ARTIG | Asteraceae | |
| Tilesius' wormwood | Artemisia tilesii Ledeb. ssp. tilesii | ARTIT | Asteraceae | |
| Tilesius' wormwood | Artemisia tilesii Ledeb. ssp. unalaschcensis (Bess.) Hultén | ARTIU2 | Asteraceae | |
| timber milkvetch | Astragalus miser Dougl. | ASMI9 | Fabaceae | |
| timber milkvetch | Astragalus miser Dougl. var. crispatus (M.E. Jones) Cronq. | ASMIC | Fabaceae | |
| timber milkvetch | Astragalus miser Dougl. var. miser | ASMIM4 | Fabaceae | |
| timber milkvetch | Astragalus miser Dougl. var. oblongifolius (Rydb.) Cronq. | ASMIO | Fabaceae | |
| timber milkvetch | Astragalus miser Dougl. var. serotinus (Gray ex Cooper) Barneby | ASMIS | Fabaceae | |
| timber milkvetch | Astragalus miser Dougl. var. tenuifolius (Nutt.) Barneby | ASMIT | Fabaceae | |
| timberline sagebrush | Artemisia rothrockii Gray | ARRO4 | Asteraceae | |
| tinged sedge | Carex tincta (Fern.) Fern. | CATI2 | Cyperaceae | |
| tiny trumpet | Collomia linearis Nutt. | COLI2 | Polemoniaceae | |
| tinypetal waxweed | Cuphea micrantha Kunth | CUMI | Lythraceae | |
| Tioga Pass sedge | Carex tiogana D. Taylor & J. Mastrogiuseppe, sp. nov. ined. | CATI5 | Cyperaceae | |
| tiplant | Cordyline fruticosa (L.) Chev. | COFR2 | Liliaceae | |
| tissue sedge | Carex hyalina Boott | CAHY2 | Cyperaceae | |
| tissueleaf hawthorn | Crataegus membranacea Sarg. | CRME11 | Rosaceae | |
| titi | Cyrilla Garden ex L. | CYRIL | Cyrillaceae | |
| Toano milkvetch | Astragalus toanus M.E. Jones | ASTO2 | Fabaceae | |
| Toano milkvetch | Astragalus toanus M.E. Jones var. scidulus Welsh & Atwood | ASTOS | Fabaceae | |
| Toano milkvetch | Astragalus toanus M.E. Jones var. toanus | ASTOT | Fabaceae | |
| toddy palm | Borassus flabellifer L. [excluded] | BOFL2 | Arecaceae | |
| toetoe | Cortaderia toetoe Zotov | COTO6 | Poaceae | |
| Toiyabe springparsley | Cymopterus goodrichii Welsh & Neese | CYGO | Apiaceae | |
| Tolmie star-tulip | Calochortus tolmiei Hook. & Arn. | CATO | Liliaceae | |
| Tolmie's onion | Allium tolmiei (Hook.) Baker ex S. Wats. | ALTO | Liliaceae | |
| Tolmin's orange lichen | Caloplaca tominii Savicz | CATO18 | Teloschistaceae | |
| Tolm's onion | Allium tolmiei (Hook.) Baker ex S. Wats. var. tolmiei | ALTOT | Liliaceae | |
| tomentose gopherweed | Baptisia lanceolata (Walt.) Ell. var. tomentosa (Larisey) Isely | BALAT | Fabaceae | |
| Tonglet's cracked lichen | Acarospora tongleti Hue | ACTO4 | Acarosporaceae | |
| Tonkin cane | Arundinaria amabilis McClure | ARAM6 | Poaceae | |
| Tonopah milkvetch | Astragalus pseudiodanthus Barneby | ASPS | Fabaceae | |
| Tonto Basin century plant | Agave delamateri W.C. Hodgson & L. Slauson | AGDE10 | Agavaceae | |
| toothache grass | Ctenium aromaticum (Walt.) Wood | CTAR | Poaceae | |
| toothache grass | Ctenium Panzer | CTENI | Poaceae | |
| toothed five eyes | Chamaesaracha crenata Rydb. | CHCR2 | Solanaceae | |
| toothed flatsedge | Cyperus dentatus Torr. | CYDE2 | Cyperaceae | |
| toothed midsorus fern | Blechnum serrulatum L.C. Rich. | BLSE | Blechnaceae | |
| toothed onion | Allium denticulatum (Ownbey & Aase) McNeal | ALDE6 | Liliaceae | |
| toothed snailfern | Cochlidium serrulatum (Sw.) Bishop | COSE7 | Grammitidaceae | |
| toothed spiderflower | Cleome serrata Jacq. | CLSE2 | Capparaceae | |
| toothed spleenwort | Asplenium trichomanes-dentatum L. | ASTR9 | Aspleniaceae | |
| toothleaf cyrtandra | Cyrtandra halawensis Rock | CYHA2 | Gesneriaceae | |
| toothpickweed | Ammi visnaga (L.) Lam. | AMVI2 | Apiaceae | |
| Toquima milkvetch | Astragalus toquimanus Barneby | ASTO3 | Fabaceae | |
| torchwood | Amyris P. Br. | AMYRI | Rutaceae | |
| toria | Brassica rapa L. var. dichotoma (Roxb. ex Fleming) Kitam. | BRRAD | Brassicaceae | |
| Torrey maple | Acer glabrum Torr. var. torreyi (Greene) Smiley | ACGLT2 | Aceraceae | |
| Torrey's amaranthus | Amaranthus torreyi (Gray) Benth. ex S. Wats. | AMTO6 | Amaranthaceae | |
| Torrey's blue eyed Mary | Collinsia torreyi Gray | COTO | Scrophulariaceae | |
| Torrey's blue eyed Mary | Collinsia torreyi Gray var. brevicarinata Newsom | COTOB | Scrophulariaceae | |
| Torrey's blue eyed Mary | Collinsia torreyi Gray var. latifolia Newsom | COTOL | Scrophulariaceae | |
| Torrey's blue eyed Mary | Collinsia torreyi Gray var. torreyi | COTOT | Scrophulariaceae | |
| Torrey's croton | Croton incanus Kunth | CRIN13 | Euphorbiaceae | |
| Torrey's cryptantha | Cryptantha torreyana (Gray) Greene | CRTO4 | Boraginaceae | |
| Torrey's milkvetch | Astragalus calycosus Torr. ex S. Wats. | ASCA9 | Fabaceae | |
| Torrey's milkvetch | Astragalus calycosus Torr. ex S. Wats. var. calycosus | ASCAC5 | Fabaceae | |
| Torrey's milkvetch | Astragalus calycosus Torr. ex S. Wats. var. monophyllidius (Rydb.) Barneby | ASCAM2 | Fabaceae | |
| Torrey's milkvetch | Astragalus calycosus Torr. ex S. Wats. var. scaposus (Gray) M.E. Jones | ASCAS | Fabaceae | |
| Torrey's saltbush | Atriplex torreyi (S. Wats.) S. Wats. |