Last updated October 1, 2009
| Name | Family | Nativity |
| Tabebuia chrysantha | Bignoniaceae | Mexico to Venezuela |
| Tabebuia chrysotricha | Bignoniaceae | Brazil, Colombia |
| Tabebuia sp. | Bignoniaceae | |
| Tagetes lemmonii | Asteraceae | SW United States |
| Taiwania cryptomerioides | Cupressaceae | SW China, Upper Burma |
| Tanacetum niveum | Asteraceae | Europe |
| Tanacetum parthenium | Asteraceae | |
| Tanacetum parthenium cv. Aureum | Asteraceae | |
| Tanacetum vulgare | Asteraceae | Europe |
| Taxodium distichum cv. Cajun Snowfall | Taxodiaceae | |
| Taxodium mucronatum | Taxodiaceae | Mexico |
| Tecoma cv. Orange Julius | Bignoniaceae | |
| Tellima grandiflora | Saxifragaceae | Cen California to Alaska |
| Tephrocactus articulatus v. papyracantha | Cactaceae | Argentina |
| Ternstroemia gymnanthera | Theaceae | India to Malaysia & Cen Japan |
| Tetradenia sp. nov. | Lamiaceae | Madagascar |
| Tetrapanax papyriferus | Araliaceae | China, Taiwan |
| Thalia dealbata | Marantaceae | SE United States |
| Thalictrum aquilegifolium | Ranunculaceae | Europe, Asia |
| Thalictrum dipterocarpum | Ranunculaceae | W China |
| Thalictrum flavum | Ranunculaceae | Eurasia |
| Thalictrum foetidum | Ranunculaceae | Cen Europe |
| Thalictrum minus ssp. saxatile | Ranunculaceae | Europe, N Asia |
| Thalictrum simplex | Ranunculaceae | Europe |
| Thelocactus sp. | Cactaceae | |
| Thelocactus sp. | Cactaceae | Mexico |
| Thelocactus tulensis | Cactaceae | Mexico |
| Thelypteris acuminata | Thelypteridaceae | E. Asia |
| Thelypteris ovata | Polypodiaceae | SW U.S., Cen Amer., W. Indies |
| Thelypteris ovata v. lindheimeri | Thelypteridaceae | Texas, Mexico |
| Thelypteris palustris | Thelypteridaceae | |
| Thelypteris puberula | Polypodiaceae | California |
| Thelypteris sp. | Polypodiaceae | |
| Thuja occidentalis cv. Rushmore | Cupressaceae | |
| Thujopsis dolabrata | Cupressaceae | Japan |
| Thymus serpyllum cv. Pink Chintz | Lamiaceae | |
| Thysanolaena maxima | Poaceae | China |
| Tillandsia streptophylla x brachycaulos cv. Eric Knobloch | Bromeliaceae | |
| Tillandsia albertiana | Bromeliaceae | NW Argentina |
| Tillandsia araujei | Bromeliaceae | Brazil |
| Tillandsia bergeri | Bromeliaceae | Argentina |
| Tillandsia butzii | Bromeliaceae | Mexico to Cen America |
| Tillandsia concolor | Bromeliaceae | Mexico, El Salvador |
| Tillandsia crocata | Bromeliaceae | Brazil, Argentina, Uruguay |
| Tillandsia cyanea | Bromeliaceae | Ecuador |
| Tillandsia duratii | Bromeliaceae | Bolivia, Paraguay, Argentina |
| Tillandsia edithae | Bromeliaceae | Bolivia |
| Tillandsia eizii | Bromeliaceae | Mexico |
| Tillandsia fasciculata | Bromeliaceae | Florida & Mexico to Colombia |
| Tillandsia fasciculata v. venosispica | Bromeliaceae | Mexico to Colombia, W. Indies |
| Tillandsia flabellata | Bromeliaceae | Mexico, Cen America |
| Tillandsia grandis | Bromeliaceae | Mexico |
| Tillandsia guatemalensis | Bromeliaceae | Mexico to Cen America |
| Tillandsia intermedia | Bromeliaceae | Mexico |
| Tillandsia ionantha | Bromeliaceae | Mexico to Costa Rica |
| Tillandsia ionantha cv. Druid | Bromeliaceae | |
| Tillandsia ionantha cv. Peanut | Bromeliaceae | |
| Tillandsia juncea | Bromeliaceae | Mexico to South America |
| Tillandsia juncea hybrid | Bromeliaceae | |
| Tillandsia lajensis | Bromeliaceae | Ecuador |
| Tillandsia leonamiana | Bromeliaceae | Brazil |
| Tillandsia mallemontii | Bromeliaceae | Brazil |
| Tillandsia nigri-stipitata | Bromeliaceae | Mexico |
| Tillandsia paucifolia | Bromeliaceae | Fla.,Cuba,Bahamas,CO to Mexico |
| Tillandsia recurvata | Bromeliaceae | S U.S. to South America |
| Tillandsia roseospicata | Bromeliaceae | |
| Tillandsia sp. | Bromeliaceae | |
| Tillandsia sp. | Bromeliaceae | Mexico |
| Tillandsia straminea | Bromeliaceae | Peru, Ecuador |
| Tillandsia streptophylla | Bromeliaceae | Mexico to Honduras, Jamaica |
| Tillandsia stricta | Bromeliaceae | Brazil |
| Tillandsia stricta x albertiana | Bromeliaceae | |
| Tillandsia tectorum | Bromeliaceae | Ecuador, Peru |
| Tillandsia tricolor | Bromeliaceae | Mexico to Costa Rica |
| Tillandsia usneoides | Bromeliaceae | SE U.S. to South America |
| Tillandsia usneoides v. major | Bromeliaceae | SE U.S. to South America |
| Tipuana tipu | Fabaceae | Brazil, Bolivia, Argentina |
| Tithonia rotundifolia | Asteraceae | Mexico to Cen America |
| Todea barbara | Osmundaceae | Aust., New Zealand, S. Africa |
| Tournefortia acutiflora | Boraginaceae | Mexico |
| Trachelium caeruleum | Campanulaceae | Europe |
| Trachycarpus fortunei | Arecaceae | China, Japan |
| Trachycarpus martianus | Arecaceae | Himalayas |
| Trachycarpus takil | Arecaceae | Himalayas |
| Trachycarpus wagnerianus | Arecaceae | Cultivated origin |
| Tradescantia pallida cv. Large Purple Heart | Commelinaceae | |
| Tradescantia sillamontana | Commelinaceae | NE Mexico |
| Tradescantia spathacea cv. Tricolor | Commelinaceae | |
| Trevesia palmata | Araliaceae | India to China |
| Trichodiadema bulbosum | Aizoaceae | South Africa |
| Trichoglottis philippinensis v. brachiata | Orchidaceae | Philippines |
| Tristania conferta | Myrtaceae | Australia(New South Wales) |
| Trithrinax acanthocoma | Arecaceae | Brazil |
| Trithrinax brasiliensis | Arecaceae | Caribbean |
| Tropaeolum majus | Tropaeolaceae | South America |
| Tulbaghia violacea | Alliaceae | South Africa |
| Tunilla corrugata | Cactaceae | Argentina |
| Turbinicarpus horripilus | Cactaceae | Mexico(Hidalgo) |
| Tylecodon paniculata | Crassulaceae | South Africa |
| Tylecodon sinus-alexandrii | Crassulaceae | South Africa |
| Tylecodon sp. | Crassulaceae |
