Weed Herbarium – by Scientific Name
| Tanacetum vulgare | tansy | Asteraceae (Compositae) - Aster or Sunflower Family |
| Taraxacum officinale | dandelion | Asteraceae (Compositae) - Aster or Sunflower Family |
| Thalictrum pubescens | see - Thalictrum polygamum | |
| Thalictrum polygamum | tall meadow rue | Ranunculaceae - Buttercup Family |
| Thlaspi arvense | field pennycress | Brassicaceae (Cruciferae) - Mustard Family |
| Tovara virginiana | Virginia knotweed | Polygonaceae - Smartweed or Buckwheat Family |
| Toxicodendron radicans | poison ivy | Anacardiaceae - Cashew Family |
| Tragopogon dubius | yellow salsify | Asteraceae (Compositae) - Aster or Sunflower Family |
| Trichostema dichotomum | bluecurls | Lamiaceae (Labiatae) - Mint Family |
| Tridens flavus | purpletop | Poaceae (Graminae) - Grass Family |
| Trifolium arvense | rabbitfoot clover | Fabaceae (Leguminosae) - Pea or Bean Family |
| Trifolium hybridum | alsike clover | Fabaceae (Leguminosae) - Pea or Bean Family |
| Trifolium pratense | red clover | Fabaceae (Leguminosae) - Pea or Bean Family |
| Trifolium repens | white clover | Fabaceae (Leguminosae) - Pea or Bean Family |
| Triodanis perfoliata | Venus lookingglass | Campanulaceae - Bluebell Family |
| Triodia flava flavus | see - Tridens flavus |
| Tussilago farfara | coltsfoot | Asteraceae (Compositae) - Aster or Sunflower Family |
| Typha latifolia | common cattail | Typhaceae - Cattail Family |