| Ambrosia cumanensis Kunth | | a | | Ambrosia cumanensis Kunth | | 2868 | |
| Ambrosia artemisiifolia L. | | a | | Ambrosia artemisiifolia L. | | 103817 | |
| Ambrosia deltoidea (Torr.) W. W. Payne | | a | | Ambrosia deltoidea (Torr.) W. W. Payne | | 103819 | |
| Ambrosia dumosa (A. Gray) W. W. Payne | | a | | Ambrosia dumosa (A. Gray) W. W. Payne | | 103821 | |
| Ambrosia grayi (A. Nelson) Shinners | | a | | Ambrosia grayi (A. Nelson) Shinners | | 103823 | |
| Ambrosia peruviana Willd. | | a | | Ambrosia peruviana Willd. | | 103824 | |
| Ambrosia psilostachya DC. | | a | | Ambrosia psilostachya DC. | | 103825 | |
| Ambrosia tomentosa Nutt. | | a | | Ambrosia tomentosa Nutt. | | 103826 | |
| Ambrosia trifida L. | | a | | Ambrosia trifida L. | | 103827 | |
| Ambrosia acanthicarpa Hook. | | a | | Ambrosia acanthicarpa Hook. | | 316547 | |
| Ambrosia bidentata Michx. | | a | | Ambrosia bidentata Michx. | | 316548 | |
| Ambrosia confertiflora DC. | | a | | Ambrosia confertiflora DC. | | 316549 | |
| Ambrosia coronopifolia Torr. & A. Gray | Ambrosia psilostachya DC. | | | Ambrosia coronopifolia Torr. & A. Gray | Ambrosia psilostachya DC. | 316550 | 103825 |
| Ambrosia spp. | | a | | Ambrosia spp. | | 317003 | |
| Ambrosia linearis (Rydb.) W. W. Payne | | a | | Ambrosia linearis (Rydb.) W. W. Payne | | 400540 | |
| Ambrosia cheiranthifolia A. Gray | | a | | Ambrosia cheiranthifolia A. Gray | | 401010 | |
| Ambrosia tenuifolia Spreng. | | a | | Ambrosia tenuifolia Spreng. | | 403696 | |
| Ambrosia maritima L. | | a | | Ambrosia maritima L. | | 413031 | |
| Ambrosia paniculata Michx. var. peruviana (Willd.) O. E. Schulz | Ambrosia peruviana Willd. | | i | Ambrosia paniculata Michx. var.peruviana (Willd.) O. E. Schulz | Ambrosia peruviana Willd. | 413034 | 103824 |
| Ambrosia elatior L. | Ambrosia artemisiifolia L. | | | Ambrosia elatior L. | Ambrosia artemisiifolia L. | 416167 | 103817 |
| Ambrosia arborescens Mill. | | a | | Ambrosia arborescens Mill. | | 416922 | |
| Ambrosia pumila (Nutt.) A. Gray | | a | | Ambrosia pumila (Nutt.) A. Gray | | 444529 | |
| Ambrosia chamissonis (Less.) Greene | | a | | Ambrosia chamissonis (Less.) Greene | | 448071 | |
| Ambrosia monogyra (Torr. & A. Gray) Strother & B. G. Baldwin | | a | | Ambrosia monogyra (Torr. & A. Gray) Strother & B. G. Baldwin | | 449252 | |
| Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin | | a | | Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin | | 449253 | |
| Ambrosia eriocentra (A. Gray) W. W. Payne | | a | | Ambrosia eriocentra (A. Gray) W. W. Payne | | 454220 | |
| Ambrosia ambrosioides (Delpino) W. W. Payne | | a | | Ambrosia ambrosioides (Delpino) W. W. Payne | | 455258 | |
| Ambrosia hispida Pursh | | a | | Ambrosia hispida Pursh | | 455260 | |
| Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var. salsola | | a | i | Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var.salsola | | 461870 | |
| Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var. fasciculata (A. Nelson) Strother & B. G. Baldwin | | a | i | Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var.fasciculata (A. Nelson) Strother & B. G. Baldwin | | 461871 | |
| Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var. pentalepis (Rydb.) Strother & B. G. Baldwin | | a | i | Ambrosia salsola (Torr. & A. Gray) Strother & B. G. Baldwin var.pentalepis (Rydb.) Strother & B. G. Baldwin | | 461872 | |