- Tall bellflower
- Tall Bluebell
- Tall fescue
- Tall flatsedge
- Tall goldenrod
- Tall meadow-rue
- Tall nightshade
- Tall oat grass
- Tall sundew
- Tall thimbleweed
- Tamarack
- Tanoak
- Taro
- Tassel Hyacinth
- Tasteless Stonecrop
- Tatarian blue lettuce
- Tatarian honeysuckle
- Tatarian Maple
- Taupata
- Tawny cottongrass
- Teddybear Cholla
- Telegraphweed
- Tenpetal Anemone
- Terebinth
- Texas bindweed
- Texas bluebonnet
- Texas Bull Nettle
- Texas creeping-oxeye
- Texas live oak
- Texas mountain laurel
- Texas Paintbrush
- Texas Persimmon
- Texas Prairie Parsley
- Texas stork's bill
- Texas Thistle
- Texas toadflax
- Texas vervain
- Texas yellow star
- Thick-leaved stonecrop
- Thick-leaved Yerba Santa
- Thicket creeper
- Thimbleberry
- Three-cornered garlic
- Three-lobe false mallow
- Three-nerved Sandwort
- Three-toothed cinquefoil
- Three-way Sedge
- Threeleaf Foamflower
- Threeleaf goldthread
- Thyme-leaved Sandwort
- Thyme-leaved speedwell
- Tidy tips
- Tievine
- Timothy grass
- Tiny bluet
- Toadshade
- Tolmie's pussy ears
- Tomato
- Tomcat clover
- Topped lavender
- Tormentil
- Touch-me-not Balsam
- Tower Mustard
- Toyon
- Trailing arbutus
- Trailing blackberry
- Trailing Daisy
- Trailing fuzzy-bean
- Trailing Rhatany
- Trailing Windmills
- Tree cholla
- Tree Mallow
- Tree privet
- Tree tobacco
- Tree-of-heaven
- Tridax Daisy
- Tropical horseweed
- Tropical milkweed
- Tropical sage
- Tuberous Comfrey
- Tuberous Jerusalem sage
- Tuberous pea
- Tufted hair grass
- Tufted Loosestrife
- Tufted vetch
- Turk's cap
- Turkey Berry
- Turkey mullein
- Turkey tangle frogfruit
- Tussock cottongrass
- Tutsan
- Twinberry honeysuckle
- Twinflower
- Twisted-leaf Yucca
- Two-leaved Toothwort
- Twoleaf miterwort
- Twoleaf nightshade