| T |
| Tagetes erecta, African marigold; American marigold; Aztec marigold |
| Tagetes patula, French marigold |
| Tagetes temurfolia, Signet marigold |
| Taiwania cryptomerioides, Taiwan cryptomeria |
| Tamarix ramosissima, Salt cedar; Tamarisk |
| Tamarix ramosissima, Tamarix |
| Tanacetum parthenium, Feverfew |
| Tanacetum vulgare, Tansy |
| Taraxacum officinale, Dandelion |
| Targetes erecta; T. patula, Marigold |
| Taxodium ascends = T. distichum var. nutans, Pond cypress |
| Taxodium distichum var. mexicana = T. mucronatum, Mexican swamp cypress |
| Taxodium distichum, Bald cypress |
| Taxus baccata 'Fastigiata Robusta', Yew |
| Taxus baccata 'Repandens', Yew |
| Taxus baccata 'Standishii', Standish yew |
| Taxus baccata, English yew |
| Taxus chinensis, Chinese yew |
| Taxus cuspiduta, Japanese yew |
| Taxus x media, Anglojap yew |
| Tecomaria capensis, Cape honeysuckle |
| Tephrosia virginiana, Goat's rue |
| Ternstroemia gymnanthera, Japanese ternstroemia (Cleyera) |
| Teucrium chamaedrys, Germander |
| Teucrium chamaedrys, Wall germander |
| Thalia dealbata, Hardy canna; Powdery thalia |
| Thalictrum aquilegifolium, Meadow rue; Columbine meadow rue |
| Thalictrum aquilegifolium, Meadow-rue |
| Thalictrum dasycarpum, Purple meadow rue |
| Thalictrum revolutum, Meadow rue |
| Thelpteris kunthii; Thelypteris normalis, Southern shield fern; River fern; Southern maiden fern; Widespread maiden fern |
| Thelpteris novaboracensis, New York fern; Tapering fern |
| Thelypteris decursive pinnata, Japanese beech fern |
| Thelypteris hexagonoptera; Phegopteris hexagonoptera, Broad beech fern; Southern beech fern |
| Thermopsis caroliniana, Southern lupine |
| Thermopsis villosa, Bush pea; False lupine; Thermopsis |
| Thuja occidentalis 'Danica', Danica arborvitae |
| Thuja occidentalis 'Degroot's Spire', Degroot's Spire arborvitae |
| Thuja occidentalis 'Filiformis', Threadleaf arborvitae |
| Thuja occidentalis 'Hetz's Midget', Hetz's Midget eastern arborvitae |
| Thuja occidentalis 'Holdmstrup', Holmstrup arborvitae |
| Thuja occidentalis 'Little Gem', Little Gem arborvitae |
| Thuja occidentalis 'Minima', Minima arborvitae |
| Thuja occidentalis 'Rheingold', Rheingold arborvitae |
| Thuja occidentalis 'Sherwood Moss', Sherwood Moss arborvitae |
| Thuja occidentalis 'Sunkist', Sunkist arborvitae |
| Thuja occidentalis, Eastern arborvitae; American arborvitae |
| Thuja orientalis 'Filiformis Erecta', Filiformis Erecta arborvitae |
| Thuja orientalis 'Westmont', Westmont arborvitae |
| Thuja plicata, Giant arborvitae; Western red cedar |
| Thunbergia alata, Black-eyed Susan vine; Clock vine |
| Thunbergia grandiflora, Blue trumpet vine |
| Thunbergia gregorii,Orange clockvine |
| Thymus herba-barona, Caraway thyme |
| Thymus leucotrichus, Juniper thyme |
| Thymus praecox, Creeping thyme; Mother of thyme |
| Thymus serpyllum, Creeping thyme; Mother of thyme |
| Thymus vulgaris, Common thyme |
| Thymus vulgaris, Garden thyme; Common thyme |
| Tiarella cordifolia, Foamflower |
| Tiarella cordifolia, Foamflower; False miterwort |
| Tigridia, Tiger or Mexican shell flowers |
| Tilia americana, American linden |
| Tilia cordata, Littleleaf linden |
| Tilia mongolica, Mongolian linden |
| Tilia platyphyllos, Bigleaf linden |
| Tilia tomentosa, Silver linden |
| Tilia x euchlora, Crimean linden |
| Tipularia discolor, Cranefly orchid |
| Tithonia rotundifolia, Mexican sunflower |
| Toona sinensis = Cedrela sinsensis, Chinese toom; Chinese cedrela |
| Torenia fournieri, Wishbone flower |
| Toxicodendron vernix, Poison sumac |
| Trachelospermum asiaticum, Asiatic jasmine |
| Trachelospermum asiaticum,Yellow star jasmine |
| Trachelospermum jasminoides,Confederate jasmine; Star jasmine |
| Trachycarpus fortunei, Windmill palm |
| Tradescantia spp., Hairy stem spiderwort |
| Tradescantia subaspera, Spiderwort |
| Tradescantia x andersonii, Spiderwort |
| Tragopogon porrifolius, Oyster-plant |
| Tragopogon pratensis, Yellow goat's-beard |
| Trichostema dichotomum, Blue curls |
| Trifolium arvense, Rabbits-foot clover |
| Trillium catesbaei, Catesby's trillium |
| Trillium cernuum, Nodding trillium |
| Trillium cuneatum, Little sweet Betsy; Hugher's trillium |
| Trillium discolor, Colorless trillium |
| Trillium erectum forma albiflorum, White erect trillium; White wakerobin |
| Trillium erectum, Trillium; Wakerobin; Red trillium |
| Trillium grandiflorum, Large flowered trillium |
| Trillium luyeum, Yellow trillium |
| Trillium pusillum, Dwarf wakerobin; Dwarf white flowering trillium |
| Trillium sessile, Red trillum; Toadshade trillium; Sessile trillium |
| Trillium spp., Trillium |
| Trillium stamineum, Blue Ridge wakerobin; Propeller trillium |
| Trillum undulatum, Painted trillium |
| Tritonia, Blazing star |
| Trochodendron aralioides, Wheel tree |
| Trollius x cultorum, Globeflower |
| Tropaeolum majus, Nasturtium |
| Tropaeolum majus,Nasturtium; Climbing nasturtium |
| Tropaeolum peregrinum, Canary creeper; Canary bird flower |
| Tropaeolum spp., Nasturtium |
| Tsuga canadensis 'Jeddeloh', Jeddeloh Canadian hemlock |
| Tsuga canadensis, Canadian hemlock |
| Tsuga caroliniana, Carolina hemlock |
| Tsuga sieboldii, Southern Japanese hemlock |
| Tulbaghia violacea, Society garlic; Sweet garlic; Pink agapanthus |
| Tulipa spp., Tulips |
| Typha angustifolia, Cattail |
| Typha angustifolia, Narrow leaved cattail |
| Typha latifolia, Common cattail |