| Ageratella A. Gray ex S. Watson, 1887 |
| Ageratella microphylla (Sch. Bip.) A. Gray ex S. Watson, 1887 |
| Ageratella microphylla var. microphylla (Sch. Bip.) A. Gray ex S. Watson, 1887 |
| Ageratella microphylla var. palmeri A. Gray, 1887 |
| Ageratella microphylla var. seemannii (Benth. & Hook. f.) A. Gray, 1887 |
| Ageratella microphylla var. sonorana B.L. Turner, 1995 |
| Ageratella palmeri (A. Gray) B.L. Rob., 1905 |
| Ageratina Spach, 1841 |
| Ageratina abronia (Klatt) R.M. King & H. Rob., 1972 |
| Ageratina acevedoana B.L. Turner, 1993 |
| Ageratina acutidentata (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina adenachaenia (Sch. Bip. ex Klatt) R.M. King & H. Rob., 1970 |
| Ageratina adenophora (Spreng.) R.M. King & H. Rob., 1970 |
| Ageratina aegirophylla (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina amblyolepis (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina areolaris (DC.) Gage ex B.L. Turner, 1997 |
| Ageratina arsenei (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina articulata (Sch. Bip. ex Hieron.) R.M. King & H. Rob., 1970 |
| Ageratina aschenborniana (Schauer) R.M. King & H. Rob., 1970 |
| Ageratina astillera (B.L. Turner) B.L. Turner, 1987 |